RS Flashcards

Question

A 64-year-old man with a history of alcoholism presents with acute onset fever and productive cough. What feature on his admission CXR would be in keeping with Klebsiella pneumonia as opposed to pneumococcal pneumonia? [Book 1 Question 36] A. Lobar consolidation. B. Parapneumonic effusion. C. Reticulonodular opacity. D. Bulging interlobar fissure. E. Spherical opacity.

Answer 1

**Bulging interlobar fissure ** Klebsiella (Gram-negative) pneumonia occurs predominantly in older alcoholic men and debilitated hospitalized patients. On the CXR it appears as a lobar opacification with air bronchograms. A bulging interlobar fissure is secondary to inflammatory exudate, increasing the volume of the involved lobe. This sign, however, is not specific and is also seen with Haemophilus influenzae and Staphylococcus aureus. Pneumococcal (Streptococcus) pneumonia typically presents as lobar consolidation. Parapneumonic effusions are seen in up to 50%. Reticulonodular opacity is a recognized atypical presentation. In children it typically presents as a spherical opacity (round pneumonia).

Answer 2

**Klebsiella** Klebsiella causes a dense pneumonia with bulging of fissures often associated with an empyema. Pneumococcal pneumonitis can also mimic this.

Answer 3

**Klebsiella pneumonia** Klebsiella pneumonia is typically seen in elderly, debilitated men and produces dense, lobar consolidation, with bulging of the fissure sometimes seen. This may also be seen with pneumococcal pneumonia, but less commonly. Klebsiella may also cause empyema (the commonest cause) and patchy bronchopneumonia. Cavitation occurs in 50%. Staphylococcus aureus pneumonia has a broncho-pneumonic pattern which may coalesce, and cavitation is common. Multiple abscesses tend to occur in intravenous drug addicts. Effusions and empyema are common. Streptococcal pneumonia occurs in all ages, especially young adults, and often produces a lobar consolidation in the basal region. Haemophilus influenzae pneumonia has no characteristic appearance. Legionnaires’ disease causes a spreading consolidation of broncho-pneumonic type.

Answer 4

**Pleural effusion** Pneumocystis carinii is the most common cause of pneumonia at this stage of the disease. Pleural effusions and lymphadenopathy are not features of PCP.

Answer 5

**Aspiration with anaerobic pneumonia** The superior segments of the lower lobes and posterior segments of the upper lobes are most affected in aspiration pneumonia. Thick-walled cavitation, frequently with air-fluid levels, can develop within weeks, mimicking post-primary TB.

Answer 6

**Diffuse bilateral ground-glass opacification** There are often diffuse bilateral ground-glass opacities and less often, focal areas of consolidation, pleural effusions, and mediastinal lymphadenopathy. Approximately 1 / 3 of patients develop pneumatocoeles, usually in the upper lobes, which usually resolve spontaneously, although infrequently can cause a pneumothorax.

Answer 7

**Infection** Bacterial causes include mycobacterium tuberculosis, mycobacterium avium intra-cellulare complex, staph aureus. Viral causes include Cytomegalovirus (CMV) and respiratory syncytial virus. Fungal causes include invasive aspergillosis.

Answer 8

**Pneumocystis jirovecii (formerly P. carinii)** * Commonest AIDS-defining opportunistic infection.CD4 <400 cells/mm 3. * CXR o Initially – normal. o Eventually – a fine para-hilar reticular or ground-glass pattern. o Pleural effusions and lymphadenopathy are uncommon. Mycobacterium avium-intracellulare primarily affects the GI tract, but chest involvement in disseminated disease typically manifests as lymphadenopathy. Diffuse reticular opacities and hilar lymphadenopathy are a feature of toxoplasmosis. Diffuse miliary nodules are seen in coccidioidomycosis. Candida pneumonia demonstrates diffuse, bilateral nonsegmental airspace opacities.

Answer 9

**Mycoplasma pneumonia**. The given clinical history is classical of mycoplasma pneumonia, which usually affects younger adults in closed populations such as prisons or the military. It is one of the most common causes of community acquired pneumonia in otherwise healthy individuals. Serum cold agglutination is positive in up to 70%. On HRCT areas of ground-glass attenuation tend to be around areas of consolidation. Centrilobular nodules and peri-broncho vascular thickening are common associated findings.

Answer 10

**Multizonal peripheral opacity** The majority of H1N1 influenza cases have been mild, but the 2009 strain can cause severe illness, including in young previously healthy persons. Radiological findings in four or more lung zones distributed bilaterally and peripherally, are significantly more often seen on the CXR obtained at admission in patients with poor outcome (requiring mechanical ventilation) compared to those with good clinical outcome. Central GGO is the most common radiographic abnormality but is not significantly associated with poor outcome. Pleural effusions are uncommon, although bilateral effusions are an independent predictor of short-term mortality in community acquired pneumonia. It should be noted that an initial normal CXR does predict against a poor outcome.

Answer 11

**Lack of pleural involvement** There is significant overlap between the features of melioidosis, pneumonia and TB. However, in melioidosis, simultaneous involvement of other organs is common. Pleural involvement such as effusion, empyema, mediastinal or hilar adenopathy are rare, making them useful differentiating features from TB. ## Footnote Melioidosis (STATdx) Infection caused by gram-negative bacillus Burkholderia pseudomallei Acute melioidosis (85%) Nodules – Small with irregular margins rapidly increase in size, coalesce, and may cavitate Consolidation – Segmental, lobar, or multi-lobar ± cavitation Pulmonary abscess Chronic melioidosis (11%) Mixed parenchymal opacities – Nodules, linear densities, and cavitation Other manifestations – Lymphadenopathy, Pleural involvement is rare Top Differential Diagnoses Staphylococcus aureus pneumonia (acute melioidosis) – pneumatocele Septic embolism (acute melioidosis) – evidence of distant infection Tuberculosis (chronic melioidosis) – apical fibrosis, granuloma

Answer 12

**Calcification** The case describes hydatid disease. Hydatid cyst of the lungs can present as solid ovoid solitary or occasionally multiple lesions on plain films. When the cyst communicates with a bronchial tree, an air fluid level is demonstrated. Several other signs are described. Whilst bilaterality is less likely (up to 20%), calcification is extremely rare (0.7%) ## Footnote Hydatid Pulmonary Cysts (STATdx) Organism Larval stage (metacestode) of cestodes (tapeworms) of genus Echinococcus (E. granulosus, E. multilocularis, E. vogeli, E. oligarthrus) Radiography * Solitary or multiple spherical or ovoid masses with well-defined borders * Variable size (1 cm to > 20 cm) * Tracheobronchial communication (rupture) o Meniscus or crescent sign: Cyst communication with bronchus (air between peri- cyst and exo-cyst) o Water lily or camalote sign: Undulating cyst membranes floating in fluid * Hydatid pneumonitis: Aspiration of hydatid material (vomica) * Pleural effusion; hydropneumothorax CT * Spherical or ovoid fluid-filled cyst * Cyst wall enhancement * May involve mediastinum, heart, chest wall, pulmonary artery, diaphragm

Answer 13

**Solitary ovoid mass with air-fluid level and floating debris** The lungs are the second most frequent site affected by hydatid disease in adults, being involved in up to 25% of cases. Commonly, a solitary ovoid or spherical mass is seen in the lower lobes. These can be quite large, measuring up to 20cm in size. There is communication with the bronchial tree, producing air–fluid levels, and the wall of the cyst may be visible, and may appear as a curvilinear opacity or floating debris. Calcification may occur within the wall of the cyst in a few cases.

Answer 14

**Bronchial atresia** * Congenital, usually discovered incidentally. * Local obliteration of the proximal lumen of a segmental bronchus * Most affected – apico-posterior segment of the left upper lobe. * Distal airway beyond atresia o Still produces mucous → mucoid impaction/mucocoele. o Ventilated by collateral air shift → Hyperexpanded and lucent, oligaemic. Congenital lobar emphysema can look similar, however there is usually no mucous plug and patients tend to present early.

Answer 15

**Focal overdistension of endotracheal tube cuff** Tracheobronchial injury secondary to blunt trauma presents with non-speciﬁc symptoms and signs. Persistent pneumomediastinum, pneumothorax or subcutaneous emphysema despite treatment is suggestive. Associated ﬁndings are fractures of the upper three ribs and posterior dislocation of the sternoclavicular joints. The diagnosis is conﬁrmed by bronchoscopy. In intubated patients, focal overdistension of the cuff of the endotracheal tube is seen when the balloon bulges into the defect. Mediastinal haematoma is more suggestive of vascular injury and chylothorax is more suggestive of thoracic duct injury. These may occur in association with tracheobronchial injury.

Answer 16

**Bronchogenic cyst** Bronchogenic cyst is an abnormality of the ventral diverticulum of the primitive foregut and is the most common foregut abnormality in the thorax. Typical appearances are of a thin-walled cyst containing mucus or ﬂuid. CT shows a well-deﬁned mass of water density in 50% (0–10 HU) or slightly higher density in the rest (10–50 HU); 86% are mediastinal and 50% peri-carinal. Pericardial cysts largely occur in the cardio-phrenic angle and are rarely mediastinal. Like bronchogenic cysts, these may change shape with position and respiration. Carcinoids occur in the lungs within bronchi and are mainly central. These are solid and may calcify. Bronchogenic carcinomas are usually solid, and centrally located in 38% of cases, where they are usually small cell tumours. These occur in the older population. Lymphadenopathy secondary to lymphoma is usually solid (unless treated) and involves multiple nodes in 95% of cases. The anterior mediastinum and retrosternal lymph nodes are usually affected ﬁrst.

Answer 17

**Squamous cell carcinoma**. Tracheal malignancies make up 1–2% of all adult intrathoracic tumours and as such are uncommon. Malignant lesions make up 90% of all tracheal malignancies. Of these, squamous cell carcinomas are the most common, presenting in elderly patients with a history of smoking. Adenoid cystic carcinoma is the next most common, presenting in a younger age group and associated with a better prognosis. Benign lesions account for less than 10%. Non-small cell lung cancer (NSCLC) would be the leading differential diagnosis if this lesion was found endo-bronchially, but not in the trachea. NSCLC can cause tracheal narrowing, but as an extrinsic lesion. The history is too brief for post-intubation stenosis to be considered and this is not associated with a soft tissue mass.

Answer 18

**Adenoid cystic carcinoma** Adenoid cystic carcinoma is the second most common malignancy of the central airways after squamous cell cancer and often presents as an endoluminal mass with an intact mucosa. Mucoepidermoid carcinoma is rare. Benign tumours are mostly of mesenchymal origin and are rare. Carcinoids in these locations are usually of the typical type.

Answer 19

**Low attenuation filling defect occupying and expanding the whole luminal diameter**. Pulmonary artery sarcoma is a rare malignancy arising from the intima of the pulmonary artery. It is frequently misdiagnosed as PE, although there are features that help differentiation. Findings that favour pulmonary artery sarcoma include a low attenuation filling defect occupying the entire luminal diameter of the proximal or main pulmonary artery, expansion of the involved arteries and extraluminal tumour extension. A filling defect forming an acute angle with the arterial wall is seen in acute PE, whereas a filling defect forming an obtuse angle indicates organizing thrombus in chronic PE. A partial filling defect surrounded by areas of contrast enhancement is a feature of embolus floating freely within the lumen. ## Footnote Low attenuation ﬁlling defect occupying and expanding the whole luminal diameter. Pulmonary artery sarcoma is a rare malignancy arising from the intima of the pulmonary artery. It is frequently misdiagnosed as PE, although there are features that help differentiation. Findings that favour pulmonary artery sarcoma include a low attenuation ﬁlling defect occupying the entire luminal diameter of the proximal or main pulmonary artery, expansion of the involved arteries and extraluminal tumour extension. A ﬁlling defect forming an acute angle with the arterial wall is seen in acute PE, whereas a ﬁlling defect forming an obtuse angle indicates organizing thrombus in chronic PE. A partial ﬁlling defect surrounded by areas of contrast enhancement is a feature of embolus ﬂoating freely within the lumen. Pulmonary Artery Sarcoma (STATdx) * Large filling defect in PA refractory to anticoagulation * Radiography o Normal if intraluminal with no PA dilatation o PA dilatation: Hilar mass o Distal oligemia, pulmonary infarction, and extraluminal extension possible * CECT: Filling defect in PA; may exhibit contrast enhancement * MR: Distinction between tumour and thrombus o Tumour more likely to enhance o Acute thrombus and tumour thrombus may enhance * Cine MR for pulmonic valve assessment * FDG PET/CT: FDG uptake within tumour

Answer 20

**Relapsing polychondritis**. Wegener’s granulomatosis and amyloidosis can both give a similar appearance to that described. Amyloid can occur as an isolated condition or as a part of systemic amyloidosis. It gives smooth narrowing, but can also give multifocal stenoses or plaques, and is frequently associated with calcification. Wegener’s commonly affects the subglottic region, giving an identical appearance, although it can cause a more irregular pattern of thickening and ulcer formation. Similarly, Wegener’s commonly affects the cartilage in the nose. However, histologically, Wegener’s causes vasculitis and granuloma formation. Mounier–Kuhn disease is also known as tracheobronchomegaly. It can be associated with tracheobronchomalacia, which may give a similar CT appearance to that described. The key difference is that this condition is characterized by a reduction in calibre of >50% of the airway lumen during expiration, as compared to inspiration. Relapsing polychondritis is a systemic condition also affecting the cartilage of the nose, ears, and joints.

Answer 21

**C. Spiculated margin** In order of decreasing likelihood, the following are features suggestive of malignancy in an indeterminate pulmonary nodule: * Spiculated margin * Size > 3cm * Age > 70 years * Malignant growth rate * Smoker * Upper lobe location

Answer 22

**A. Age 30-39** Benign growth rate, benign calcification, age < 39 (answer) and a non-smoking history are the features most likely to favour a benign nodule.

Answer 23

**B. Contrast enhancement > 10HU** Degree of contrast enhancement is much higher in cavitating lung tumours. Adjacent bronchiectasis is more often seen in aspergillomas.

Answer 24

**High signal on T2-weighted images** PMF has a peripheral location which moves towards the hilum on follow-up imaging. Calcification and cavitation may also be seen. PMF lesions can be FDG-avid on PET-CT. However, high signal in a mass on T2-weighted images is strongly suspicious for malignancy.

Answer 25

**Enhancing central mass** Aspergilloma appears as a solid mass in a thin-walled cavity, which lies in a dependent position and is mobile. A crescent-shaped airspace is typical. It may calcify and be associated with pleural thickening. In contrast, cavitating malignancy often has irregular thick-walled margins with a central mass that often enhances and is fixed and non-mobile. Calciﬁcation may occur in relation to malignancy but is usually adjacent to, rather than in, the lesion and is usually seen with a scar carcinoma. Neither causes high-density lesions. Adjacent bronchiectasis is more often seen when there has been previous infection such as tuberculosis, producing a cavity in which an aspergilloma develops.

Answer 26

**Chondroid calcification** Calcification occurs in approximately 20% of cases and is almost pathognomonic if of the chondroid ‘popcorn’ type.

Answer 27

**Central ’popcorn’ calcification** Irregular or spiculated margin, eccentric or stippled calcification, doubling time of 20–400 days, contrast enhancement of more than 15 HU, and high uptake (SUV > 2.5) on PET-CT are all features associated with a malignant lesion. Diffuse, central nodular, and popcorn-like calcification, doubling time of more than 400 days, contrast enhancement of less than 15 HU, and low uptake (SUV < 2.5) on PET-CT are associated with benign lesions.

Answer 28

**Hamartoma** Hamartomas are usually well-defined solitary lesions < 4cm. The presence of fat in the lesion is a diagnostic feature, although may not be present in a hamartomatous nodule in up to 1/3 of cases. The lesions may grow slowly over time.

Answer 29

**Presence of fat** Hamartomas are usually seen in the periphery of the lungs (two-thirds) with 10% being endobronchial. Calcification is seen in 15%, often popcorn type. Cavitation is rare but fat is seen in 50%. Carcinoids are usually located centrally and are endobronchial. Calcification is seen in one-third and they rarely cavitate. They do not contain fat and show prominent enhancement following contrast, as they are vascular. Hamartomas: peripheral, Ca, rarely cavitate, fat +, don’t enhance. Carcinoid: central, Ca, rarely cavitate, no fat, enhance.

Answer 30

**Lobulated, 3 cm mass with calcification and fat, in a peripheral location** Hamartomas are seen in 0.25% of the population and are the commonest benign lung tumour. Two-thirds are found peripherally. They are rarely multiple or cavitatory. Fifteen per cent calcify (classically popcorn) and 50% contain fat. Option (a) is more typical of carcinoid, while (c) is suggestive of multiple granulomas, probably secondary to chickenpox. Option (e) is characteristic of pulmonary arteriovenous malformation.

Answer 31

**Bronchioloalveolar carcinoma**. In this disease, the tumour spreads along the alveolar septa without invading alveolar walls. The air in the alveoli is replaced by tumour cells, producing consolidation and GGO. Mediastinal lymphadenopathy is rare; pleural effusion is common. Diagnosis is made by sputum/bronchial washing cytology or lung biopsy. It mimics other causes of air-space opacification such as pneumonia, haemorrhage, oedema etc. Disseminated adenocarcinoma, choriocarcinoma, or lymphoma might produce identical CT findings. PET-CT is often negative in the case of both bronchioloalveolar carcinoma and carcinoid tumours of the lung. Carcinoid is in the form of a focal mass, not diffuse consolidation. Klebsiella pneumonia classically produces enlargement of the involved lobe, bulging of the fissures with the propensity for cavitation, and abscess formation. Small cell carcinoma is usually positive on PET-CT. TB is usually PET positive and has a predilection for the upper lobes, or apical segments of the lower lobes.

Answer 32

**Indium-111 octreotide SPECT–CT**. Bronchial carcinoid * Younger patients * Not associated with smoking * Central, hilar, perihilar, or endobronchial (unlike peripheral nodule of carcinoid tumour) * Classical features o a smooth nodule, narrowing or compressing the bronchus, or o an endobronchial lesion o Both have stippled calcification and demonstrate avid enhancement. The degree of enhancement can simulate a pulmonary vascular malformation, which can be assessed with angiography, although MR angiography would be less invasive in this case. The definitive tissue diagnosis is commonly reached with bronchoscopy, but this can be associated with massive haemorrhage because of the vascular nature of this tumour. As such radiolabelled imaging, which is sensitive in 86% of patients, is a less invasive option. FDG PET is often negative in cases of carcinoid because of the low metabolic activity of this tumour. MRI characteristics of bronchial carcinoid have been well described but will be unlikely to significantly progress the diagnostic pathway in this case.

Answer 33

**Adenocarcinoma**. These are all classical features of adenocarcinoma. Bronchoalveolar carcinoma is a subtype of adenocarcinoma. This comprises 2–10% of lung cancers. There are three subtypes: a solitary nodule (41%), multifocal nodules (36%), and peripheral consolidation (23%). Squamous cell carcinoma is only slightly less prevalent than adenocarcinoma. It cavitates in 86% of cases and typically occurs centrally. Small cell carcinoma comprises 18% of lung cancers. It usually presents on plain film radiography as hilar and/or mediastinal adenopathy. CT often detects lung opacities. Giant cell carcinoma is a poorly differentiated subtype of NSCLC that is capable of rapid growth and early metastasis.

Answer 34

**CT scan within 12 months for both. If unchanged, both need a follow-up CT within a further 12 months.** ## Footnote British Thoracic Society Guideline on Solitary Pulmonary Nodule (2015) Solid nodules 1. Nodules with clear features of benign disease can be discharged a. Hamartoma b. Peri-fissural nodules 2. Nodule size: <5 mm diameter or <80 mm3 volume → Discharge 3. Nodule size: ≥5 to <6 mm diameter → CT at 1 year from baseline a. stable on basis of 2D diameter → CT 2 years from baseline with volume assessment b. stable on volumetry → Discharge c. volume doubling time >600 days → Discharge or CT surveillance up to patient d. volume doubling time 400-600 days → Consider biopsy or CT surveillance e. volume doubling time ≤400 days → Further workup or Definitive Mg 4. Nodule size: ≥6 mm diameter or ≥80 mm3 volume → CT at 3 months from baseline a. volume doubling time ≤400 days → Further workup or Definitive Mgt b. volume doubling time >400 days → CT surveillance 5. Nodule size: ≥8 mm diameter or ≥300 mm3 volume a. low risk of malignancy (<10% Brock) → CT surveillance b. higher risk of malignancy (≥10% Brock) → PET-CT and Herder model i. <10% risk of malignancy → CT surveillance ii. 10-70% risk of malignancy → Image-guided biopsy iii. >70% risk of malignancy → Excision or non-surgical management Subsolid nodules These include nodules with a partly solid or partly ground glass component. 1. Nodule size: <5 mm diameter or <80 mm3 volume → discharge 2. Nodule size: ≥5 mm diameter or ≥80 mm3 volume a. If there is previous imaging i. nodules stable for 4 years are discharged ii. nodules stable for less than 4 years undergo further surveillance and malignancy risk assessment b. if no previous imaging is available, CT in 3 months i. Resolved → Discharge ii. Stable 1. low risk of malignancy (<10% Brock) → CT 1, 2, 4 years 2. higher risk of malignancy (≥10% Brock) → D/W patients a. surveillance thin section CT at 1, 2 and 4 years b. image guided biopsy c. resection or non-surgical treatment iii. Growth/altered morphology → Resection or non-surgical 1. offer repeat CT at 1, 2 and 4 years from baseline if the patient does not want resection/therapy

Answer 35

**None of these**. [This answer does not apply to the most recent staging where small cell and non-small cell carcinoma are staged under the same system]. The TNM staging of lung cancer is not commonly used for staging small cell lung cancer. This cell type is particularly aggressive and often has occult metastases at the time of malignancy. The mainstay of treatment is with chemoradiotherapy, with imaging only used to stage disease as intrathoracic (limited or extensive) or extra-thoracic.

Answer 36

**Stage 2B ** The TNM deﬁnitions, on which the staging system is based, were recently updated in 2010. In this update, the nodal classiﬁcations were not changed, but the T staging was updated, as was M staging. Sub-classiﬁcations were added to T1, with lesions <2 cm being T1a and lesions between 2 and 3 cm being T1b. Lesions between 3 and 5 cm are T2a and between 5 and 7 cm are T2b. Lesions over 7 cm are T3, as are synchronous lesions within the primary lobe, as in this case. Multiple lesions within the primary lobe were formerly T4. In this question, the lymph node is not enlarged by size criteria and is not FDG avid on PET. While this may yet still be involved, on imaging ﬁndings alone, this lesion should be classed as N0. The absence of metastases is obviously M0. Thus, this patient is T3 N0 M0, which corresponds to stage 2b. T2b N1 tumours are also in this stage. Stage 2a lesions are T2a N1 or T2b N0. Stage 3a lesions are T3 or less with N2 disease or T3 N1 lesions. ## Footnote Lung Cancer Staging (8 th Edition – 2017) T Staging T1 < or = 3cm [Substage a, b, c – 1, 2, 3 cm] T2a [3.1-4 cm] or main bronchus without carina T2b [4.1-5 cm] or visceral pleura, hilar fat, or atelectasis T3 [5-7 cm] or synchronous nodule in the same node***, parietal pleura/pericardium, chest wall, phrenic nerve T4 [>7 cm] or visceral pericardium, mediastinum, vertebra, diaphragm, carina N Staging N1 ipsilateral peripheral nodes up to hila N2 ipsilateral mediastinal, carina N3 any contralateral, or supraclavicular/scalene of any side M Staging M1a Intra-thoracic, Pleural/pericardial effusion M1b Single organ extra-thoracic M1c Multiple organ extra-thoracic Overall All M1c → Stage IVB Other M’s → Stage IVA N1 → Start from IIB until T3, then IIIA N2 → Start from IIIA until T3, then IIIB N3 → Start from IIIB until T3, then IIIC T1 a, b, c → IA 1, 2, 3 T2 a, b → IB, IIA T3 → IIB T4 → IIIA

Answer 37

**T2 N2 M0** The T stage is T2, as the lesion is over 3cm but there is no chest wall or mediastinal invasion or other associated feature. The nodes at the right hilum (N1) and in the subcarinal space (N2) are signiﬁcantly enlarged, whereas the node in the aortopulmonary space (N3) is not (<10mm short axis), hence the N stage is N2.

Answer 38

**Central location** BAC can present in a local form as a mass, usually peripheral, subpleural in location or as diffuse persistent/progressive consolidation in patients with a history of smoking. The area of consolidation is often of low attenuation on CT due to copious mucin production. It is the second most common type of malignancy associated with cavitation.

Answer 39

**Bronchioloalveolar carcinoma** BAC usually presents as a peripheral, subpleural mass or persistent patch of consolidation. All the others can present as endobronchial lesions.

Answer 40

**Squamous cell cancer** The case describes a Pancoast tumour for which squamous is the most common cell type.

Answer 41

**Bronchogenic carcinoma** The changes described indicate lymphangitis carcinomatosis. Whilst similar appearances are seen in sarcoidosis, the changes are usually in the upper lobe and pleural effusion is rare. In heart failure, the interlobar septal thickening is usually smooth and usually bilateral. In EAA, pleural effusion is rare, and changes are more broncho centric and bilateral. The polygonal structure is usually distorted in both EAA and cryptogenic fibrosis, where the changes are again subpleural.

Answer 42

**A. Bronchogenic carcinoma** A typical carcinoid is a small mass (< 2.5cm) with no associated lymphadenopathy. Calcifications are seen in up to 26% of cases on CT. The iceberg phenomenon is the presence of a small endobronchial component associated with a larger extra-bronchial component.

Answer 43

**Invasion of the pericardium** T3 disease features include a tumour of any size less than 2cm from the carina, invasion of the parietal pleura, chest wall, diaphragm, mediastinal pleura, pericardium, pleural effusion or satellite nodule in the same lobe. T4 disease is characterised by invasion of the heart, great vessels, trachea, oesophagus, vertebral body, carina, or the presence of a malignant pleural effusion.

Answer 44

**Shift of the previously central trachea to the left** All the other changes are expected changes at this stage following a pneumonectomy. However, contralateral shift of the trachea may be indicative of a post-surgical bronchopleural fistula.

Answer 45

**Focal paravertebral muscle uptake** FDG uptake occurs at many sites due to physiological uptake. Muscle uptake is variable, but usually occurs throughout a muscle when physiological. Focal muscle uptake is of concern, although benign causes are not uncommon. Diffuse thyroid uptake is usually physiological, but may indicate thyroiditis, whereas focal thyroid uptake may be malignant in 20–50% of cases. Tonsillar uptake if diffuse and symmetrical is likely to be benign, but asymmetrical or focal uptake requires further assessment. Caecal uptake, if diffuse, is probably due to lymphoid uptake, but, again, focal uptake must be assessed further. FDG uptake in the uterine cavity is usually due to menstruation.

Answer 46

**Obtain tissue diagnosis** Wherever possible, deﬁnitive diagnosis should be obtained, as it will enable the best possible treatment. Dependent upon the cause of the obstruction, the correct therapeutic option can then be employed. Radiotherapy often gives a good response, but, in small-cell lung cancer, chemotherapy often gives good results. Stenting should be used when radiotherapy or chemotherapy has failed. Surgical therapy is usually reserved for benign causes where conservative options have failed.

Answer 47

**Mediastinal Small Cell Carcinoma** Diaphragmatic elevation with paradoxical motion is usually due to phrenic nerve paralysis. Mediastinal tumours are one of the commonest causes. Pancoast’s tumours invade the brachial plexus, though they can uncommonly invade the phrenic nerve. Eventration tends not to show paradoxical motion, though it can if large. Strokes may cause diaphragmatic elevation, but due to bilateral innervation of the diaphragm, this is not usually due to phrenic nerve involvement and has other causes, such as weakness of chest wall muscles.

Answer 48

**18 FDG PET/CT scan** Although the imaging features suggest a benign nodule, malignancy cannot be excluded, and further investigation is warranted. CT enhancement studies may be helpful in solid nodules but are of less value when a nodule is cavitating. An 18 FDG PET/CT scan has both high sensitivity and speciﬁcity in assessing solitary pulmonary nodules, with accuracy over 90%. There is a high speciﬁcity for a lesion that shows no FDG uptake being benign. Follow-up is still recommended to ensure no growth and exclude a very low-grade tumour. Interval CT may be considered an option, but in a young patient, unless there are exceptional circumstances, aiming to characterize the lesion is considered more appropriate. MRI is of no proven value in the evaluation of lung nodules.

Answer 49

**Dual time point assessment of SUV** Dual time point assessment involves measuring the SUV at two time points to assess for change. In malignant lesions the SUV rises with time, whereas with benign lesions this tends to remain static. The maximum SUV corrected for lean body mass or weight is the standard measurement used for assessment of metabolic activity of lesions on PET. The metabolic tumour burden is currently not used in clinical practice. The assessment of uptake in the peripheral and central areas of a lesion is not a recognized technique.

Answer 50

**Lymphangitis carcinomatosis** Lymphangitis carcinomatosis is tumour cell accumulation within connective tissue, causing lymphatic obstruction. This leads to interstitial oedema. The chest radiograph may be normal, but there is often reticulonodular change with Kerley A and B lines. An ipsilateral hilar or mediastinal mass may be seen. Pulmonary ﬁbrosis has a peripheral predominance and tends to be bilateral. Extrinsic allergic alveolitis and histiocytosis tend to be bilateral. Sarcoidosis usually produces a more nodular pattern and there is predominance in the upper lobes. Polygonal structures on CT are uncommon in sarcoidosis.

Answer 51

It is possible to estimate postoperative lung function (FEV 1 (forced expiratory volume in 1 s)) with ventilation and perfusion scintigraphy, either in isolation or combination. However, ventilation scintigraphy is the best predictor of postoperative FEV1. This does underestimate the value; therefore, patients with borderline lung function should not necessarily be denied surgery because of the result. CT and MRI have not been shown to be helpful in assessing postoperative lung function.

Answer 52

**Pleural fibroma** HPOA * Malignant Causes o Primary bronchogenic carcinoma especially NSCLC o Pulmonary metastasis from extra-thoracic malignancies * Benign Causes o Pleural fibroma (answer) o Bronchiectasis

Answer 53

**HPOA with pleural fibroma** The periosteal reaction is typical of hypertrophic osteoarthropathy (HOA), which has many causes, both intra- and extra-thoracic. It is associated with bronchogenic carcinoma and malignant mesothelioma, but features of the described lesion are not typical of either of these, and are more in keeping with pleural ﬁbroma. These are associated with HOA in 20–35% of cases and rarely with clubbing. They may arise in pleura adjacent to the chest wall or in a ﬁssure and can vary in size from 2 cm to 30cm in diameter. Tuberculosis is a rare cause of HOA. Rheumatoid arthritis is associated with bilateral periosteal reactions, but not HOA.

Answer 54

**Nodularity of the pleural thickening** On multivariate analysis, the CT findings of rind-like pleural involvement, mediastinal pleural involvement and pleural thickness > 1 cm were independent findings in differentiating malignant pleural mesothelioma from other malignant pleural disease, with specificity values of 0.85, 0.67 and 0.82, respectively.

Answer 55

**The diaphragmatic disease noted on MRI**. The finding of peritoneal disease upstages this tumour to Stage 4, which is inoperable. CT is the main imaging modality in malignant mesothelioma, which is sufficient in a lot of cases that are obviously inoperable on this modality alone. MRI has been shown to be superior to CT in the detection of local invasion, hence the normal CT appearance in this case, where peritoneal disease was noted on MRI. PET or PET-CT are better at detecting nodal disease than either CT or MRI. As such, in some cases all three modalities are necessary to stage disease.

Answer 56

**Subdiaphragmatic Extension** Imaging findings of deep myocardial invasion, multifocal chest wall invasion or subdiaphragmatic extension are contraindications to surgery. Patients with stage 1-3 may be surgical candidates but not necessarily cured. MRI findings of focal thickening and enhancement of the interlobular fissures are useful signs in the detection of early malignant pleural disease.

Answer 57

**Melanoma** Pericardial effusion, thickening or mass may indicate metastatic involvement of the pericardium. Most neoplasms have a low-signal intensity on T1-weighted images and a high signal intensity on T2-weighted images, except for metastatic melanoma. The most common tumours to metastasize to the pericardium are breast and lung, followed by lymphomas and melanomas.

Answer 58

**Choriocarcinoma** Choriocarcinoma, renal carcinoma, and melanoma are causes of haemorrhagic pulmonary metastases.

Answer 59

**Melanoma metastases**. The GGO surrounding a nodule is known as the ‘halo’ sign and represents perilesional haemorrhage. Melanoma metastases can both cavitate and produce perilesional haemorrhage. Differential diagnoses for Halo’s sign (Perilesional haemorrhage or cellular infiltration) * Infection: Angio invasive fungi (classically Aspergillus, also Candida, Mucor), mycobacteria, rickettsia, viruses (e.g., Varicella zoster, Herpes simplex, Cytomegalovirus), and septic embolism * Inflammatory: Granulomatosis with polyangiitis, eosinophilic pneumonia, cryptogenic organizing pneumonia, endometriosis * Neoplastic: Kaposi sarcoma, pulmonary adenocarcinoma with lepidic features, vascular metastases (e.g., angiosarcoma, choriocarcinoma, osteosarcoma) * Iatrogenic: Post-transbronchial biopsy, catheter-induced pulmonary pseudoaneurysm Cavities with Halo Wegener’s granulomatosis Lymphoma, Bronchoalveolar carcinoma Squamous cell carcinoma Haemorrhagic Mets Cavities without Halo Rheumatoid lung Eosinophilic granuloma Lung abscesses Churg–Strauss syndrome is not associated with the halo sign and cavitation is rare.

Answer 60

**Renal cell cancer** RCC

Answer 61

**Choriocarcinoma** In order of decreasing frequency, pulmonary metastases arise from choriocarcinoma, hypernephroma/Wilms’ tumour, Ewing’s/rhabdomyosarcoma, and testicular tumours.

Answer 62

**Lung** In order of decreasing frequency, metastases to the pleura arise from lung, breast, lymphoma, ovary and stomach cancers.

Answer 63

**metastases secondary to osteosarcoma** Osteosarcoma pulmonary metastases are uncommon (seen in 2% of cases) and present as multiple masses which may calcify. There is a high incidence of associated pneumothorax. Wilms’ tumours may also produce multiple pulmonary masses and may be associated with pneumothorax but are not known to calcify. Testicular tumours may produce calciﬁed lung metastases but are not associated with pneumothorax. Varicella pneumonia shows patchy consolidation in the acute phase, with multiple, small, calciﬁed nodules in the chronic phase. Abscesses may present as multiple masses but rarely calcify and often cavitate.

Answer 64

**Normal chest radiograph** In chronic asthma, most patients (73%) have normal appearances on chest radiographs between acute episodes. Features such as bronchiectasis or parenchymal scarring may be seen, especially with episodes of repeated infection. Hyper-expansion and peri-bronchial cuffing are features seen during acute exacerbations of asthma.

Answer 65

**Alpha-1 antitrypsin deficiency** Alpha-1 antitrypsin is a glycoprotein synthesized in the hepatocytes, which acts as a proteolytic inhibitor. In the absence of alpha-1 antitrypsin, the enzyme elastase released by neutrophils and alveolar macrophages acts unopposed and digests the basement membrane. There is rapid progressive deterioration of lung function due to severe pan-acinar emphysema, which shows basilar predominance (due to gravitational distribution of pulmonary blood flow). The alveolar destruction is accelerated in smokers. Cirrhosis of the liver is a complication.

Answer 66

**Lack of bronchial tapering** Whilst all the above can be seen in patients with bronchiectasis, a lack of progressive tapering of the bronchi is the most sensitive (80%).

Answer 67

**Decreased calibre of vessels in lucent areas** In multiple focal mosaic lung attenuation * If the blood vessels in the lucent areas are smaller, then the lucent areas are probably abnormal. o The paucity of vessels in these regions may be secondary to focal air-trapping or poor ventilation and subsequent reflex vasoconstriction. If areas of lucency are exaggerated on expiratory scans (air-trapping), then this is the hallmark of small airways disease. o Alternatively, if the areas of lucency do not become more prominent on the expiratory scans, small airways disease is not the likely cause. In this situation, the inhomogeneous lung attenuation is probably secondary to changes in vessel calibre, and secondary to pulmonary hypertension, including chronic PE, emphysema, or inflammatory vasculopathies. * If the blood vessels in the regions of relative lucency are equal in size to vessels in surrounding areas, the regions of relative opacity are most likely abnormal, e.g., areas of GGO.

Answer 68

**Chronic thromboembolic disease** Mosaic perfusion is caused by abnormalities of ventilation, or vascular obstruction. Expiratory scans help to distinguish causes by establishing whether there is air trapping. With no air trapping present, pulmonary emboli of any cause are most likely. Air trapping would suggest airway disease such as bronchiolitis obliterans, or other causes of small airway obstruction such as bronchiectasis or cystic fibrosis.

Answer 69

**The lucent areas have abnormally small vessels** Mosaic perfusion refers to areas of altered attenuation on CT and reflects vascular obstruction or abnormal ventilation. Differentiation from ground-glass opacification can be difficult but can usually be done by assessment of the centrilobular vessels. In comparing ‘lucent’ and ‘opaque’ areas, the area in which the vessels appear larger is generally the normal area, though this may be a difficult differentiation to make in practice, as the vessels may be of the same size throughout the lung. In mosaic perfusion, the vessels appear abnormal in the ‘lucent’ area, whereas, in ground-glass opacification, the vessels appear abnormal in the ‘opaque’ area. Expiratory scans may then help to distinguish airway causes from vascular causes, by the presence of air trapping, which is seen with airway disease.

Answer 70

**Fertility assessment** The presence of dextrocardia, nasal polyposis and bronchiectasis raises the possibility of Kartagener’s syndrome. This is immotile/dysmotile cilia syndrome and may also present with deafness and infertility. There is also an association with transposition of the great vessels, pyloric stenosis, post-cricoid web and epispadias.

Answer 71

**Respiratory bronchiolitis interstitial lung disease (RB-ILD).** RBILD is a disease of smokers and the centrilobular nodules reflect chronic inflammation in the respiratory bronchioles. GGO may occur and is typically multifocal and upper lobe predominant. Reticulation is uncommon and fibrosis is not a typical feature. The typical features of UIP are reticulation, honeycombing, and traction bronchiectasis, with a basal and subpleural predominance. NSIP has overlapping features with UIP, but GGO is more common and honeycombing less common. DIP is a rare disease and, like RBILD, associated with smoking. The cardinal feature is GGO, with a basal and peripheral predominance. Sometimes small cystic areas can be seen within the areas of GGO. Progression to fibrosis/honeycombing is rare. COP was formerly known as bronchiolitis obliterans organizing pneumonia (BOOP). The main finding on HRCT is consolidation, which is usually multifocal and bilateral. It typically has a lower zone and peripheral predominance but can affect any lobe. Dilated airways are often seen on HRCT with air bronchograms mimicking acute pneumonia. There may also be GGO and reticulation, but lung volumes are usually maintained.

Answer 72

**Predominant ground-glass opacification** Although Ground glass opacification (GGO) can be commonly seen in USIP, it is found in 75-100% of cases of NSIP, where it is usually bilateral, symmetrical and subpleural in two-thirds of patients and has a lower zone predominance on over 50%. Honeycombing is not a major feature, although it can occur in up to 50%. Typical HRCT features of USIP include reticulation, honeycombing and traction bronchiectasis with basal and subpleural predominance.

Answer 73

**Lymphocytic interstitial pneumonia**. LIP is a benign lymphoproliferative disorder that is also associated with AIDS, autoimmune thyroid disease, and Castleman’s syndrome. Lymphomas may arise in some cases. On HRCT: * Randomly distributed thin-walled cysts. * GGO, centrilobular/subpleural nodules, septal thickening. * Eventually larger nodules (>2 cm), consolidation, and architectural distortion may develop. * Mediastinal and hilar lymphadenopathy (2/3) o The presence of mediastinal and hilar lymphadenopathy (two-thirds) and septal thickening help distinguish from Langerhans cell histiocytosis. o The presence of centrilobular nodules assist in the differentiation from LAM. Birt–Hogg–Dube syndrome: * AD * Facial fibrofolliculomas * Malignant renal tumours * Thin-walled pulmonary cysts * Spontaneous pneumothorax.

Answer 74

**Cryptogenic organizing pneumonia**. An area of GGO surrounded by a ring of consolidation describes the ‘ring halo’ sign. This is not specific to COP, but has been described in tuberculosis, active sarcoidosis, cryptococcosis, and blastomycosis. However, it has been found that granulomatous infectious diseases and sarcoidosis, which cause the ‘ring halo’ sign, result in a nodular ring, whereas COP results in a smooth-walled ring. COP is rapidly responsive to steroids, but the latter can have deleterious effects in infectious diseases. Thus, it has been suggested that a nodular ring can be used as a discriminator. COP (also known as idiopathic BOOP) is a patchy organizing pneumonia caused by bronchiolar obstruction by plugs of loose organizing connective tissue that may wax and wane. The main finding of COP is consolidation, seen in 90% and usually multifocal and bilateral. In 50% the consolidation is subpleural or peri-broncho-vascular. It has a lower zone predominance but can affect any lobe. Dilated airways are often seen on CT and air bronchograms give the appearance of acute pneumonia. GGO is a prominent pattern in 60%. Linear opacities occur in isolation or in association with multifocal areas of consolidation. Nodules are seen in 30–50% and lung volumes are preserved in 75%. COP is a clinical-pathological entity and is diagnosed when the correct clinical picture and radiological findings are present. If these features are uncertain, lung biopsy is required. Organizing pneumonia can be idiopathic (COP) or secondary to viral infection, toxic fume inhalation, RA, systemic lupus erythematosus (SLE), organ transplantation, drug reaction, or chronic aspiration. The hallmark of obliterative bronchiolitis is air-trapping and hyperinflation. It has many causes, including RA and other connective tissue diseases.

Answer 75

**GGO**. This is a salient feature of NSIP and is seen in almost all cases. Diffuse nodules are very infrequent in NSIP. If centrilobular nodules are present, one should think of other forms of diffuse lung disease such as respiratory bronchiolitis interstitial lung disease (RBILD) or hypersensitivity pneumonitis. If multiple cysts are present, again other diffuse lung disease should be considered, such as lymphocytic interstitial pneumonia (LIP), DIP, lymphangioleiomyomatosis, and pulmonary Langerhans cell histiocytosis. Areas of air-trapping would be a more typical finding in hypersensitivity pneumonitis, rather than NSIP. Pleural effusions are not a typical finding in NSIP.

Answer 76

**A lack of oral/genital ulcers** Hughes-Stovin syndrome, also known as incomplete Behçet’s disease, overlaps in radiologic and histopathologic findings, but there is an absence of oral and genital ulcerations.

Answer 77

**Sarcoid**. There are numerous causes of bilateral hilar lymphadenopathy (BHL) and in the absence of further clinical information, sarcoid would always feature high in the list of differentials. However, the finding of BHL in association with paratracheal adenopathy is classical for this disease.

Answer 78

**Sarcoid** These are characteristic features of sarcoid on HRCT. Peri-lymphatic nodules (beading along the fissures) and architectural distortion are commonly found.

Answer 79

**Posterior mediastinal lymph nodes** All the above are features of mediastinal lymphadenopathy in sarcoidosis. Whilst sarcoidosis can involve different mediastinal and hilar groups, posterior mediastinal lymphadenopathy is a feature of NHL.

Answer 80

**Centrilobular region**. In sarcoid, the granulomatous nodules are typically distributed along the lymphatics and are therefore seen along the bronchovascular bundles, interlobular septa, major fissures, and subpleural regions. The centrilobular region of the secondary pulmonary lobule contains the bronchiole and therefore conditions that cause peribronchiolar inflammation, such as subacute EAA and RB-ILD more often cause centrilobular nodules. These are often ground glass in attenuation and ill-defined, unlike the more solid appearing granulomatous nodules of sarcoid. Rarely sarcoid can cause centrilobular nodules because of the presence of peribronchiolar granulomas, but the other mentioned locations are much more typical.

Answer 81

**Scleroderma** Whilst haemoptysis may be a presentation in tuberculosis and Wegener’s and bi-basal fibrosis maybe seen in all the above except tuberculosis (where apical fibrosis is the more likely feature), scleroderma is the only condition resulting in a patulous lower oesophageal sphincter, oesophageal shortening, and stricture formation.

Answer 82

The presence of ground glass opacification (without evidence of traction bronchiectasis) in the middle lobe and lingula is strongly associated with active alveolitis. Basal ground glass shadowing is a non-specific finding and a poor predictor of alveolitis.

Answer 83

**Lower zone fibrosis** The case describes neurofibromatosis I, which is associated with lower zone fibrosis and thin-walled bullae, mainly in the upper zones. Apart from the pulmonary changes, skeletal abnormalities involving the ribs and spine and mediastinal masses may also be seen.

Answer 84

**Pleural effusion** Pleural effusion is the commonest thoracic manifestation of rheumatoid arthritis, much more common in men (M = 9:1). It is unilateral in most cases. The fluid is an exudate with low sugar content and is often seen in the absence of other pulmonary changes.

Answer 85

**Pleural effusion** Whilst all the above are seen in SLE, pleural effusions are the commonest radiographic abnormality.

Answer 86

**Pleural Effusion** Between 2% and 54% of patients with rheumatoid arthritis have pulmonary abnormalities. Pleural abnormalities are most frequent, being either an effusion (unilateral in 92% of cases) or pleural thickening (usually bilateral). Fibrosis occurs in 30% of patients with pulmonary involvement. Nodules are unusual and seen in advanced disease. They are usually peripheral and may cavitate. Bronchial abnormalities are seen in 30% of patients with rheumatoid lung and include bronchiectasis and bronchiolitis obliterans. Other findings include pulmonary arterial hypertension and heart failure secondary to carditis/pericarditis.

Answer 87

**Sjogren syndrome** Whilst pulmonary fibrosis is a feature of all the above conditions, bronchiectasis is most likely seen in Sjogren syndrome.

Answer 88

**Granulomatosis with Polyangiitis** This condition is associated with the findings described, including bilateral nodules and cavitation, particularly in the context of a history of sinusitis.

Answer 89

**Ankylosing spondylitis** Pulmonary changes occur in ankylosing spondylitis in 1% of patients, with reticulonodular abnormality in the upper zones progressing to conﬂuent opaciﬁcation and ﬁbrosis. There may be apical bullous formation and cavitation mimicking tuberculosis. No granulomatous disease is seen. Ossiﬁcation of spinal ligaments is typical in ankylosing spondylitis. Upper-zone ﬁbrosis is seen with tuberculosis, sarcoidosis, and chronic extrinsic allergic alveolitis, but spinal ossiﬁcation is not a feature of these conditions. The reciprocal is true of Reiter’s syndrome.

Answer 90

**Interstitial lung disease** All of these features can occur, but 65% of patients have ﬁbrosis on CT, although only 30% of patients with systemic sclerosis have clinically signiﬁcant lung disease. The commonest interstitial lung disease is nonspeciﬁc interstitial pneumonitis, seen in two-thirds of cases. This is less coarse and extensive than usual interstitial pneumonitis, the other type seen, and is almost always associated with ground-glass opaciﬁcation. Other respiratory features seen in systemic sclerosis are organizing pneumonia, pulmonary haemorrhage, pleural thickening, and malignancy.

Answer 91

**Symmetrical hilar lymphadenopathy** Differentiation of tuberculosis and sarcoidosis can be difﬁcult clinically and radiologically. The presence of symmetrical hilar lymphadenopathy is seen more often with sarcoidosis than with tuberculosis. Pleural effusions, and cavitating and calciﬁed lesions are much more common with tuberculosis. Consolidation can be seen in both conditions, though it is again more commonly seen in tuberculosis.

Answer 92

**Mid-zone predominance of reticulation** Sarcoidosis is seen more commonly in females and affects the thorax in 90% of cases. It usually produces adenopathy with or without parenchymal disease. There is a mid-zone predominance with irregular septal thickening, peri-lymphatic nodules, ground-glass opaciﬁcation, traction bronchiectasis, and honeycombing. Rheumatoid lung is more common in males and mostly presents with pleural abnormalities, usually an effusion. It may present with an interstitial ﬁbrotic picture with a lower-zone predominance. Multiple large nodules of up to 7 cm in diameter are seen with rheumatoid lung. Cardiomegaly may be seen with both sarcoidosis and rheumatoid, because of congestive cardiac failure.

Answer 93

**Loffler syndrome** This is described as simple eosinophilic pneumonia but is of unknown aetiology. Pathologically, there is interstitial and alveolar oedema. Patients are usually asthmatic/atopic but have mild or no symptoms. Classical chest radiograph appearance is of fleeting infiltrates with transient and shifting peripheral consolidation.

Answer 94

**Homogenous peripheral airspace consolidation** Chronic eosinophilic pneumonia is characterised by the presence of homogenous peripheral airspace consolidation on CT, whereas the peripheral consolidation in Churg-Strauss has a tendency towards lobular distribution and is often associated with centrilobular nodules within the ground glass opacity.

Answer 95

Small centrilobular nodules Churg–Strauss syndrome is rare, though pulmonary abnormalities are a common feature of the condition. Typically, airspace and airway patterns are seen with the following features – centrilobular nodules, ground-glass opacities, bronchial wall thickening, bronchiectasis, consolidation, and septal thickening. Lymphadenopathy may be seen in the mediastinum and at the hila but is not a common feature. Large nodules may occur, but a tumour-like mass is not a feature. Pleural effusions and bullae are not seen.

Answer 96

**Eosinophilic pneumonia**, resolving pulmonary oedema, desquamative interstitial pneumonia and sarcoidosis are causes of reverse bats wings peripheral infiltrates. Causes of perihilar bats wings infiltrates include pulmonary oedema, proteinosis, sarcoidosis, lymphoma, Goodpasture’s syndrome and alveolar cell carcinoma.

Answer 97

**Chronic eosinophilic pneumonia**. ## Footnote * The radiological ‘photographic negative’ of pulmonary oedema. * Middle age, females > males. * Common history of atopy * Histology – filling of alveolar spaces with inflammatory eosinophilic infiltrates in alveolar spaces, and in interstitium and peripheral blood eosinophilia. * A dramatic response to steroid therapy within days. ABPA and acute eosinophilic pneumonia do produce blood eosinophilia ABPA – bronchiectasis and mucus plugging with the possibility of mosaic perfusion in addition to peripheral consolidation, Acute eosinophilic pneumonia – diffuse GGO, deﬁned nodules, smooth interlobular septal thickening, and often the presence of pleural effusion. Simple pulmonary eosinophilia = Löfﬂer’s syndrome Peripheral transient parenchymal consolidation accompanied by eosinophilia. Minimal or no pulmonary symptoms CXR appearances change within one to several days and spontaneous resolution occurs within one month. Eosinophilic granuloma is nodular/cystic, a pulmonary form of Langerhan’s cell histiocytosis, and should not be confused with the eosinophilic pneumonias.

Answer 98

**Wegener’s granulomatosis** The combination of nosebleeds and cavitatory nodules is very suggestive of Wegener’s granulomatosis, especially with renal impairment. In the lungs there is often patchy alveolar infiltration, pleural effusions and cavitatory nodules. Systemic lupus erythematosus produces similar appearances by the same mechanism of vasculitis. Sarcoidosis produces many lung changes but cavitatory nodules are rare. Metastatic nasopharyngeal carcinomas are usually squamous cell tumours and can produce cavitatory metastases, but primary tumours usually present with nasal obstruction, although they may cause epistaxis. Renal impairment is not a feature. Multiple abscesses are not usually associated with epistaxis and present acutely, typically in intravenous drug users.

Answer 99

**Loeffler’s syndrome** Loeffler’s syndrome is of unknown aetiology and is characterized by areas of non-segmental consolidation, which are peripherally situated and transient. Histiocytosis produces ill-defined nodules which cavitate, first producing thick-walled and then thin-walled cysts. Klebsiella pneumonia usually affects the upper lobes, producing dense, lobar consolidation, sometimes with bulging fissure and empyema. Pseudomonas pneumonia is patchy but extensive and usually in the lower lobes. Lipoid pneumonia is segmental and homogeneously dense, and changes only slowly.

Answer 100

**Tubular finger-like opacities** Allergic bronchopulmonary aspergillosis (ABPA) is hypersensitivity to aspergillus in people with asthma. Typical features are of a migratory pneumonitis, predominantly in the upper lobes. It may cause bronchiectasis and upper-zone fibrosis, which are features also seen in extrinsic allergic alveolitis (EAA). Tubular opacities, indicating mucus plugging, are seen in ABPA, but not in EAA. Centrilobular nodules are seen in EAA, along with mosaic perfusion and patchy ground-glass change. Pleural effusions are rarely seen in EAA and not in ABPA.

Answer 101

**C. Amiodarone**. The pulmonary findings could equally be caused by NSIP and cardiac failure, among other causes. However, the high attenuation of the liver and spleen is due to deposition of amiodarone, which contains iodine. Amiodarone, methotrexate, and bleomycin all may cause pulmonary toxicity. Pulmonary toxicity occurs in 5–10% of patients on amiodarone, usually within months of starting therapy. The prognosis is good, with most patients improving after discontinuation of therapy. NSIP is the most common manifestation of amiodarone-induced lung disease. Pleural inflammation is an accompanying feature and can manifest as pleural effusion. COP is less common and typically occurs in association with NSIP. A distinctive feature of amiodarone toxicity is the occurrence of focal, homogenous pulmonary opacities. They are typically peripheral in location and of high attenuation at CT, due to the incorporation of amiodarone into the type II pneumocytes. The combination of high attenuation within the lung, liver, and spleen is characteristic of amiodarone toxicity. RA can produce many pulmonary sequelae: pulmonary nodules, pleural effusion, fibrosis, obliterative bronchiolitis, and COP. Methotrexate can be used to treat RA and psoriasis, and as chemotherapy for various cancers. NSIP is most common, and COP is seen less frequently. Bleomycin is a chemotherapy agent used in the treatment of testicular carcinoma, among others. Diffuse alveolar damage (DAD) is its most common manifestation, with NSIP and COP being less common. The prognosis is poor, with most patients dying of respiratory failure within 3 months of the onset of symptoms.

Answer 102

**A. Nitrofurantoin**. Drugs causing pulmonary eosinophilia 1. Nitrofurantoin 2. Penicillamine 3. Sulphasalazine 4. NSAID, and para-aminosalicylic acid. Drugs associated with diffused alveolar damage Bleomycin and cyclophosphamide, busulphan, carmustine, gold salts, and mitomycin. In early DAD, HRCT typically shows scattered or diffuse areas of GGO. Fibrosis typically develops within 1 week and if progressive can cause marked architectural distortion and honeycombing. Amiodarone and methotrexate are associated with an NSIP pattern on HRCT. Carmustine and chlorambucil can also cause this appearance. With early disease, HRCT scans may show only scattered or diffuse areas of GGO. Later, findings of fibrosis (traction bronchiectasis, honeycombing) predominate in a basal distribution. Other recognized patterns of drug-induced lung injury include a COP pattern and diffuse pulmonary haemorrhage.

Answer 103

**C. Pulmonary alveolar proteinosis.** ## Footnote This is rare, but most commonly develops in a primary idiopathic form (90%), chieﬂy in middle aged smokers, with a male predominance. It can also occur secondary to industrial dust exposure, immunodeﬁciency disorders (HIV and iatrogenic causes), and, as in the question, secondary to underlying haematological malignancies. There is also a congenital form. The radiological ﬁndings are often out of proportion with the disease severity. The HRCT ﬁndings described are those of ‘crazy-paving’. There is a wide differential diagnosis for this, including pulmonary oedema, pneumocystis pneumonia, haemorrhage, bronchoalveolar carcinoma, ARDS, lymphangitis carcinomatosis, radiation or drug-induced pneumonitis, hypersensitivity pneumonitis, and pulmonary veno-occlusive disease. The distinguishing factor in our case is the history of leukaemia; this would also predispose to infection, but the BAL has ruled pneumocystis out. In alveolar proteinosis, BAL or lung biopsy reveals intra- alveolar deposits of proteinaceous material, dissolved cholesterol, or eosinophilic globules. Symptomatic treatment includes whole lung lavage and multiple procedures may be required. Pulmonary Alveolar Proteinosis (STATdx) Causes Autoimmune (90%) Secondary to immunodeficiency or haematological malignancy Congenital Radiology 1. Ground-glass pattern 2. Crazy-paving pattern 3. Consolidation

Answer 104

**B. Alveolar proteinosis** The typical chest radiographic findings are of bilateral central and symmetric lung opacities with relative sparing of the apices. A range of findings are possible however, including asymmetric opacities and diffuse consolidation. The most common elevated serologic marker is LDH, although this is non-specific. There can be a marked disparity between the often-moderate symptoms and extensive radiologic findings.

Answer 105

**c. pulmonary alveolar proteinosis** Pulmonary alveolar proteinosis is due to accumulation of proteinaceous material in the alveoli, which causes hypoxia. There is a variable combination of airspace and interstitial changes, but diffuse ground-glass opacification and ‘crazy-paving’ are typical. A geographic distribution is also described. Lack of other features (such as cardiomegaly, lymphadenopathy, and effusion) helps to distinguish it from infection and oedema. The lack of precipitating event and slow onset makes acute respiratory distress syndrome unlikely. Hypersensitivity pneumonitis often shows no abnormality on chest radiograph, but high-resolution CT shows surprisingly marked ground-glass change and centrilobular nodules with peripheral sparing.

Answer 106

**b. Multiple bilateral small cysts** Phacomatoses - a group of neurocutaneous syndromes consisting of * Neurofibromatosis I and II, * Sturge–Weber syndrome, * von Hippel Lindau syndrome, * Osler–Rendu–Weber syndrome and * Tuberous sclerosis. The above features describe multiple renal angiomyolipomas, which are a feature of tuberous sclerosis. These patients may demonstrate multiple thin-walled cysts with lower zone fibrosis (forme fruste of LAM).

Answer 107

**E. Histiocytosis** Osteosarcoma, Wilms’ tumour and histiocytosis are causes of pulmonary nodules with pneumothorax.

Answer 108

**E. Langerhans’ cell histiocytosis (LCH)** Early findings include interstitial infiltrate centred on the small airways, leading to the development of small parenchymal nodules. These are typically irregular, of soft-tissue density, and measure 1-5mm in diameter, although some may be over 1cm in size.

Answer 109

**D. Pulmonary Langerhans cell histiocytosis** ## Footnote Pulmonary Langerhans cell histiocytosis * Young adult, smoker. * Symptoms o Non-productive cough, dyspnoea. o Less commonly fatigue, weight loss, pleuritic chest pain, fever. * CXR o Initially, small irregular nodules, bilateral, symmetric, with upper lobe predominance, with sparing of costophrenic angles. o Later stage, coarse reticular and reticulonodular pattern o May present with recurrent pneumothorax. o Pleural effusion is uncommon but may occur with pneumothorax. * HRCT o Cysts and nodules in a characteristic distribution with normal intervening lung. o Interstitial ﬁbrosis and honeycombing are seen in advanced stages. * Treatment o Smoking cessation o Steroids o Chemotherapeutic agents o Lung transplantation. * Prognosis – variable.

Answer 110

**a. Lymphangioleiomyomatosis** The cysts in LAM are thin-walled air-containing cysts, rather than cavitation in nodules.

Answer 111

**c. tuberous sclerosis** The lung is involved in 5% of patients with tuberous sclerosis, with symptoms usually occurring in adult life, and it is predominantly women who are affected. There is interstitial fibrosis in the lower lungs with miliary nodular changes, which progress to honeycomb lung. Recurrent pneumothoraces occur in 50% of cases. Chylothorax may also be seen. Preservation of the lung volumes with honeycombing is seen in histiocytosis, neurofibromatosis and lymphangiomyomatosis, as well as tuberous sclerosis.

Answer 112

**d. lymphangiomyomatosis** Lymphangiomyomatosis is exclusively seen in women of child-bearing age and is worsened in pregnancy. Classically, it causes coarse reticular/reticulonodular interstitial changes, and patients develop recurrent chylous effusions and pneumothoraces. Lung volumes are preserved or may be increased (the only interstitial lung disease with increased lung volumes). It may progress to honeycombing. Histiocytosis usually affects men, and causes cystic change in the upper lobes, small nodules and septal thickening. Tuberous sclerosis has similar features to histiocytosis but is associated with skin changes, reduced IQ, and epilepsy. Neurofibromatosis tends to cause progressive fibrosis, but effusions and pneumothoraces are uncommon. Idiopathic pulmonary fibrosis tends to affect the older age group with a reticulonodular pattern.

Answer 113

**d. histocytosis** Honeycombing is seen with all these conditions, but the combination of normal volumes, cysts and peri-bronchial nodules is very suggestive of histiocytosis. Often the lung bases are preserved early in the disease but the whole lung is eventually involved. Lung volumes in usual interstitial pneumonitis are reduced. Neurofibromatosis causes interstitial fibrosis with little nodularity. Tuberous sclerosis causes lower zone fibrotic change with miliary nodules that progresses to honeycombing. Lymphangiomyomatosis produces coarse reticular change due to cyst formation, but nodularity is not seen. Pneumothoraces and pleural effusions are seen with neurofibromatosis, tuberous sclerosis and lymphangiomyomatosis.

Answer 114

**b. coal worker’s pneumoconiosis with progressive massive fibrosis** The history of mining (dust exposure) with small nodules in the upper zones is typical of pneumoconiosis. The sausage-shaped mass is characteristic of progressive massive fibrosis (PMF), although malignancy cannot be excluded. PMF is often seen to have reduced nodularity surrounding it, as it incorporates the surrounding nodules and migrates towards the hilum. Tuberculosis usually produces a generalized distribution of 2–3mm nodules in its miliary form, often with lymphadenopathy. Metastases from primary lung cancer are not uniformly small (though they can be in thyroid cancer and melanoma). Chronic extrinsic allergic alveolitis produces fibrotic changes in the mid and lower zones.

Answer 115

**c. Posterior costophrenic sulci** The question is leading to chronic hypersensitivity pneumonitis as the most likely underlying diagnosis. The fibrotic process, in advanced stages, affects both the subpleural lung and the peri-bronchovascular interstitium. There may be honeycomb formation at the lung bases, but unlike usual interstitial pneumonia/idiopathic pulmonary fibrosis, the honeycombing typically spares the most extreme posterior costophrenic sulci. Classically, the fibrotic process is more pronounced in the mid and upper lung zones.

Answer 116

**d. Subpleural** Subpleural pulmonary fibrosis associated with asbestos exposure is seen mainly in a subpleural distribution towards the lung bases.

Answer 117

**e. Cystic spaces** Although ground glass changes and small centrilobular nodules are present in hypersensitivity pneumonitis, there are no cystic spaces, or thickening of the bronchovascular bundles.

Answer 118

**e. Hypersensitivity pneumonitis** Characteristic HRCT features in hypersensitivity pneumonitis include ground glass opacity, air trapping and centrilobular ground glass opacities.

Answer 119

**b. Areas of air-space shadowing** Acute extrinsic allergic alveolitis is predominantly a type III hypersensitivity reaction. There is poor correlation between the clinical presentation and the radiological changes. Lymphadenopathy is unusual in the acute phase but is seen more commonly in recurrent disease. The early changes are mainly in the mid zones, but the fibrosis that develops in chronic extrinsic allergic alveolitis is mainly in the upper zones. In the acute phase, diffuse air-space shadowing or multiple opacities are seen.

Answer 120

**Siderosis**. - Iron Oxide, Welders - Multiple small centrilobular nodules but is not usually associated with any symptoms or fibrosis. - If combined with silica dust it can cause silico-siderosis, which can be associated with fibrosis. Silicosis and coal workers pneumoconiosis, secondary to inhalation of silica dust and washed coal dust, respectively, show similar features on CT. This is usually the presence of 2–5 mm nodules, mainly involving the upper and posterior lung zones. Large opacities (>1 cm) indicate progressive massive fibrosis. Calcification in lymph nodes can occur and eggshell calcification is more typical in silicosis. Berylliosis is a chronic granulomatous lung disease caused by exposure to beryllium dust or fumes. CT findings are like other granulomatous lung diseases, such as sarcoid. Fibrosis may therefore occur. Asbestosis is pulmonary fibrosis secondary to inhalation of asbestos fibers.

Answer 121

**Rounded atelectasis**. Rounded atelectasis is an infolding of pleura associated with atelectasis, which occurs in the posterior lower lobes and abuts an area of pleural thickening. Often a ‘comet’s tail’ of bronchovascular markings is seen curving towards the hilum. Bronchogenic carcinoma may occur with asbestos exposure but is usually of bronchioalveolar cell type and has a latent period of 25–35 years. Round pneumonia produces spherical consolidation with air bronchograms. Silicosis may cause conglomerate masses, usually in the mid or upper zones, or progressive massive fibrosis, but reticulonodular changes predominate.

Answer 122

**Progressive massive fibrosis**. Silicosis is due to inhalation of silicon dioxide particles, and radiographic changes of chronic silicosis are seen 10–20 years after exposure. The nodules are typically less than 10mm, compared with sarcoid nodules, which can be more variable in size (acinar type 6–7mm, alveolar type >10mm). Calcified hilar lymph nodes (eggshell pattern), traction bronchiectasis, and honeycombing occur in both conditions and are not discriminatory. Progressive massive fibrosis is a complication of the pneumoconioses and is not seen in sarcoidosis.

Answer 123

**Dilated pulmonary veins**. This patient has developed Eisenmenger syndrome with reversal of his longstanding left-to-right shunt across the ASD. All the features listed except dilated pulmonary veins are generally present.

Answer 124

**Fat embolism**. Seen in: - Long bone fractures - Major burns - Pancreatitis - Haemoglobinopathy - Tumors - Liposuction Locations: - Pulmonary - Cerebral - Cutaneous symptoms (petechiae secondary to coagulopathy) The time lapse between the traumatic event and the radiographic abnormalities is usually 1–2 days, which allows differentiation from traumatic contusion. The radiographic findings resemble ARDS, although a peripheral distribution of consolidation is described. V/Q scanning will reveal multiple peripheral perfusion defects. In practice, it is the clinical features such as the rash, confusion, and coagulopathy, as well as the presence of a fracture, which raise the suspicion of fat embolism.

Answer 125

**Fat embolism** In a patient who has sustained multiple fractures, fat embolism should always be considered when a patient is short of breath in the presence of a normal chest radiograph. This manifests on a V/Q scan as mottled peripheral perfusion defects. Chest radiograph remains normal for up to 72 hours, when discoid atelectasis, diffuse alveolar infiltrates, and consolidation may develop. Fat embolism may precede the development of acute respiratory distress syndrome. Pulmonary contusions usually manifest earlier, within the first 24 hours.

Answer 126

**Infarction results in linear scarring** HRCT often reveals ground-glass opacification, which does not have a lobar distribution and may have a scattered or mosaic pattern. Adults tend to have lower lobe or multilobar involvement, compared to the upper lobe pattern more often seen in children. Microvascular occlusion causes a reduction in the vascular markings and infarction results in linear scarring.

Answer 127

**RV/LV diameter ratio**

Answer 128

**No further investigation or anticoagulation required**. * In the setting of low probability with positive D-dimer, a good quality negative CTPA has a negative predictive value of 96%. * In the setting of a high pre-test probability, a negative CTPA should be followed with either venous ultrasound or MR venography (PIOPED).

Answer 129

**Perfusion defect with a rim of surrounding normally perfused lung**. Multiple bilateral perfusion defects with a normal ventilation scan are the classic diagnostic findings in PE. Occluding pulmonary emboli produce segmental perfusion defects that extend to the pleural surface. As other conditions may also produce perfusion defects, the ventilation scan improves specificity. Non-embolic lung disease will typically have both perfusion and ventilation abnormalities, resulting in matched defects. V/Q scans are categorized as normal, low, intermediate, or high probability. A perfusion defect that matches ventilation and CXR abnormalities in size and location is a triple matched defect. A triple matched defect in the middle or upper lung zones is in keeping with low probability but rises to intermediate probability when in the lower zones. A single moderate matched V/Q defect, but with a normal CXR, is also of intermediate probability. No perfusion defect is in keeping with a normal scan and four moderate segmental defects is a high probability scan. A perfusion defect with a rim of surrounding normally perfused lung is known as the stripe sign and corresponds to low probability for PE, as PE perfusion defects should extend to the pleural surface and have no overlying stripe of perfused lung. PIOPED II Criteria (Sn 77.4%, Sp 97.7%) Pulmonary embolism present (high probability) * Two or more large mismatched segmental perfusion defects or the arithmetic equivalent of moderate and/or large defects Nondiagnostic (low or intermediate probability) * All other findings not falling into the pulmonary embolism present or absent categories Pulmonary embolism absent (normal or very low probability) * No perfusion defects * Nonsegmental perfusion defects (e.g., pleural effusion at the costophrenic angle, cardiomegaly, elevated hemidiaphragm, hilar enlargement, linear atelectasis), without other perfusion defects in either lung * Perfusion defects smaller than corresponding chest radiographic opacity * One to three small subsegmental perfusion defects * Two or more matched ventilation and perfusion defects with a regionally normal chest radiograph and some areas of normal perfusion elsewhere * Solitary triple matched defect (matched ventilation and perfusion defect with corresponding chest radiographic opacity) in a single segment in the middle or upper lung zone * Stripe sign (a stripe of perfusion peripheral to a defect, best seen on tangential view) * Large pleural effusion (occupying one-third or more of the pleural cavity), without other perfusion defects in either lung

Answer 130

**Large, segmental, matched defect with similar-sized opacity on chest radiograph** With ventilation–perfusion scintigraphy, matched segmental defects are considered low probability. When there is a similar-sized area of opacification on the chest radiograph, which indicates 'triple match,' this becomes intermediate probability. Matched non-segmental defects, reverse mismatch, and multiple small perfusion defects are all indicators of low probability. Two large segmental perfusion defects that are not matched are considered high probability.

Answer 131

**Venous ultrasound**. For pregnant patients, venous ultrasound is recommended before imaging tests with ionizing radiation are performed. Up to 29% of pregnant patients with PE will have a positive venous ultrasound, obviating the need for further imaging. The majority of the PIOPED II investigators currently recommend V/Q scanning over CTPA in the evaluation of PE in pregnant patients. The foetal dose with V/Q is similar to that with CTPA, although the effective dose per breast is much greater with CTPA. MRI requires further evaluation and gadolinium-based contrast agents have not been proven to be safe in pregnancy. The role of catheter angiography is probably limited to those patients requiring mechanical thrombectomy. It should be noted that even a combination of CXR, lung scintigraphy, CTPA, and pulmonary angiography exposes the foetus to approximately 1.5mGy of radiation, which is well below the accepted limit of 50 mGy for the induction of deterministic effects in the foetus.

Answer 132

**Pelvic ultrasound** Even with no clot seen, the loss of respiratory variation with continuous flow suggests a more proximal occlusion. As the limb swelling is unilateral, the most likely site of occlusion would be in the pelvic veins.

Answer 133

**Unilateral regional oligemia** This represents Westermark’s sign and is associated with PE, not pulmonary oedema. The other features are consistent with cardiac failure. Focal right upper lobe oedema is associated with mitral regurgitation, where the regurgitant jet produces locally increased pressures in the right upper lobe pulmonary veins with a focal increase in oedema in that region. This can mimic consolidation on plain film but will be seen to resolve after diuresis. Pleural effusions may be unilateral in cardiac failure.

Answer 134

**PE with inability to achieve or maintain therapeutic anticoagulation** Other absolute indications include PE/DVT with contraindication to anticoagulation, PE/DVT and complications of anticoagulation, and recurrent DVT/PE despite anticoagulation.

Answer 135

**CT pulmonary angiogram ** The differential diagnosis is between pulmonary embolus or pneumonia with effusion, with investigation directed accordingly. High-resolution CT would be unhelpful due to lack of contrast. A staging chest CT is performed in the aortic phase of contrast so pulmonary arteries will be suboptimally seen. CT pulmonary angiogram is the best investigation in this case because when there is consolidation/opacification present on a chest radiograph, a V/Q scan has a high likelihood of being nondiagnostic. Conventional pulmonary angiography is a high-risk procedure and is rarely performed in modern practice.

Answer 136

**Chronic thromboembolic disease** Mosaic perfusion is caused by abnormalities of ventilation or vascular obstruction. Expiratory scans help to distinguish causes by establishing whether there is air trapping. With no air trapping present, pulmonary emboli of any cause are most likely. Air trapping would suggest airway disease such as bronchiolitis obliterans or other causes of small airway obstruction such as bronchiectasis or cystic fibrosis.

Answer 137

**Peripheral mural filling defect forming obtuse angle with wall** Chronic emboli usually form peripheral flattened defects, forming obtuse angles with the arterial wall. Secondary changes such as hypertrophy of the right atrium and ventricle, cardiomegaly, and pulmonary hypertension may be present. Recanalization or collateral formation is suggestive of chronicity, and clot calcification also indicates chronicity.

Answer 138

**Trans-oesophageal echocardiogram** In this clinical scenario, the patient is most likely to have multiple septic emboli secondary to intravenous drug use. Given the multiple pulmonary abscesses and pneumonia, tricuspid endocarditis should be considered, and an echocardiogram should be performed. Trans-oesophageal echocardiogram is more sensitive to valvular vegetations and should be the investigation of choice.

Answer 139

**CT pulmonary angiogram has a higher total body dose but a lower uterine dose** The total body dose for CT pulmonary angiogram is approximately 2–3 times higher than for V/Q scanning. However, the uterine, and therefore fetal, dose is higher with V/Q scanning. Although low-dose V/Q techniques can reduce this, the uterine dose remains higher. The risk of death from pulmonary embolus outweighs any radiation risk to the patient or fetus.

Answer 140

**Bilateral pleural effusions**. The underlying diagnosis is ARDS. Causes * Direct lung injury (e.g. pneumonia, toxic gas inhalation, aspiration) * Indirect lung injury (e.g. trauma, sepsis, pancreatitis). Diagnosis * PaO2 /FiO2 < 200 mmHg AND * No evidence of left heart failure Therefore, the presence of a pleural effusion casts doubts on the diagnosis. Appearances * Can mimic pulmonary oedema * Bronchial dilatation is frequently seen on CT. * The alveolar changes are heterogenous with a density gradient in both the cranio-caudal and antero-posterior directions. * Radiographic changes tend to be absent for the first 24 hours (except direct lung injury), then increase to remain static for days or weeks, and then begin to resolve. * Pneumothorax can occur secondary to ventilation. * Reticular changes, with a predilection for non-dependent lung, may be secondary to the underlying process or to barotrauma (seen in 85% of survivors in one study; the mortality of ARDS is approximately 50%).

Answer 141

**Patchy ill-defined opacities** Acute respiratory distress syndrome (ARDS) commences with interstitial oedema, progressing to congestion and extensive alveolar, and interstitial oedema and haemorrhage. The chest radiograph is often normal for the ﬁrst 24 hours, before patchy opacities appear in both lungs. These progress to massive airspace consolidation over the following 24–48 hours. True volume loss, atelectasis, cardiomegaly and effusions are not seen in ARDS.

Answer 142

**Pulmonary oedema** Inhalation of noxious gases, including smoke, produces focal or diffuse pulmonary oedema. With smoke this may be delayed by 1–2 days. Bronchiolitis obliterans may then ensue after 1–3 weeks, especially with chemical inhalation.

Answer 143

**Reticular changes in the anterior aspects of the lungs** In most patients who survive acute respiratory distress syndrome (ARDS), there is no functional deﬁcit. Where investigated, however, the most common abnormality detected is a reticular pattern in the ventral non-dependent lung. The extent of this is negatively related to the extent of opaciﬁcation in the acute phase and strongly related to the duration of mechanical ventilation. Bronchiectasis is seen in both acute and chronic phases but is less common than reticular change. Upper lobe ﬁbrosis is not associated with ARDS.

Answer 144

**Posterior aspect of the lungs**. The stem of the question is pointing towards ARDS during the ICU admission, resulting in pulmonary ﬁbrosis. Classically HRCT shows relative sparing of the posterior aspect of the lungs. This pattern of sparing is unusual in other causes of peripheral ﬁbrosis and is an important clue to the aetiology. During the acute and subacute phases of ARDS in the supine patient, the dependent portions of the lungs usually demonstrate extensive consolidation and atelectasis. It is postulated that these areas may be protected from the long-term effects of barotrauma and high oxygen exposure as they are essentially non-aerated during the acute and subacute phases.

Answer 145

**Greater association with congenital abnormalities** The association with congenital abnormalities is greater in extra-lobar (50%) than intra-lobar sequestration (15%). Other features of extra-lobar sequestration include systemic venous drainage, having its own pleural investment, and being symptomatic in the first 6 months of life.

Answer 146

**Intra-lobar sequestration** The presence of systemic vascular supply to the infected segment and the history of recurrent infections makes intra-lobar sequestration the most likely diagnosis. ## Footnote Pulmonary Sequestration (STATdx) * Definition: Lung tissue not connected to tracheobronchial tree, with anolomous systemic arterial supply. * Synonyms: Rokitansky lobe * Pathologic Subtypes: o Extra-lobar sequestration ▪ More common in foetus ▪ Separate pleural covering ▪ Systemic venous drainage ▪ Histology: Dilated bronchioles, alveoli, and subpleural lymphatics o Intra-lobar sequestration ▪ Less common in foetus ▪ No separate pleural covering ▪ Pulmonary venous drainage ▪ Histology: Chronic inflammation and fibrosis * Sites: o 85-90% - supradiaphragmatic, 10-15% subdiaphragmatic o 80% left-sided, lower lung predominant * Imaging o USG ▪ Homogeneously echogenic, solid mass ▪ May be isoechoic to lung in late gestation ▪ Feeding vessel arising from aorta most specific imaging finding o Intrathoracic bronchopulmonary sequestration (BPS) ▪ Echogenic, triangular lesion adjacent to diaphragm ▪ Ipsilateral pleural effusion in 6-10% o Abdominal BPS ▪ Stomach displaced anteriorly by echogenic mass ▪ Separate from adrenal gland o MR ▪ Homogeneously T2 bright mass ▪ T2 flow void feeding vessel ▪ Not always necessary * Top Differential Diagnoses o Congenital pulmonary airway malformation (CPAM) o Hybrid lesion (BPS + CPAM) o Neuroblastoma * Clinical Issues o 1/3 of prenatally diagnosed lung masses o Associated anomalies in up to 50% - DHP, Congenital Diaphragmatic hernia * Treatment for hydrothorax +/- hydrops o Embolization o Resection postnatally * Prognosis – Excellent.

Answer 147

**Intra-lobar sequestration** Active tuberculosis, consolidation, atypical pulmonary hamartomas, and scars may cause false positive results. Uncomplicated sequestration will not demonstrate FDG uptake.

Answer 148

**Left hilar enlargement** The case describes Swyer–James syndrome (Macleod syndrome). This is a post-infectious constrictive bronchiolitis which causes a small, hyperlucent lung with bronchiectasis and air trapping in expiration. The number and size of pulmonary vessels are also diminished, resulting in a small ipsilateral hilum.

Answer 149

**MacLeod syndrome** MacLeod or Swyer-James syndrome manifests as hyper-lucency with features of air trapping. The affected lung in proximal interruption of a pulmonary artery is often as opaque, or slightly opaquer, than the contralateral lung, and there is no evidence of air trapping.

Answer 150

**Enclosed in visceral pleura** Bronchopulmonary sequestration is a malformation consisting of a nonfunctioning lung segment with no communication to the bronchial tree and a systemic arterial supply. The intra-lobar type accounts for 75% of cases. It is enclosed in visceral pleura and presents in adulthood with pain, repeated infection, cough, and haemoptysis. The extra-lobar type is enclosed in its own pleura and presents in infancy with feeding difficulties, respiratory distress, cyanosis, and congestive heart failure. Systemic venous drainage is seen in 80% of cases of extra-lobar type, but only in 5% of cases of intra-lobar type.

Answer 151

**Atypical thymoma** Thymoma Whilst the ultimate differentiation between these lesions is pathological, there are several clinical and imaging features that can help limit the differential if present. Whilst benign thymoma, atypical thymoma, and thymic carcinoma can all present as focal mass lesions in the thymus, Benign thymoma would not demonstrate the locally aggressive features found on this patient’s scan. Atypical thymoma is a locally aggressive lesion with benign features on pathology; it has a better prognosis than thymic carcinoma. Atypical thymoma, thymic carcinoma, thymic lymphoma, and malignant thymic germ cell tumours can all be locally aggressive. The presence of mediastinal lymphadenopathy, invasion of the great vessels, or distant metastases are uncommon for atypical thymoma, but are features of the other three tumours; none of these were present in this case. The ﬁnal key differentiating feature in this case to indicate atypical thymoma over the other differentials is the presence of myasthenia gravis. As thymic lymphoma and malignant germ cell tumours are not of thymic origin, they would not cause this. It is rarely a feature of thymic carcinoma.

Answer 152

**Thymoma** This case describes the typical features of a thymoma. Thymic hyperplasia and thymic carcinoma are usually ill-defined abnormalities. The signal from the lesion is not typical for a thymic cyst or thymolipoma.

Answer 153

**Thymus** The thymus is the only extra-nodal site where Hodgkin’s lymphoma commonly occurs, and almost all cases are of the nodular sclerosing subtype.

Answer 154

**Mediastinal enlargement** Mediastinal lymph node enlargement is a feature of primary tuberculosis. The other features are seen with reactivation or fibrocavitary TB. Miliary TB can be seen in any phase with haematogenous dissemination, but primary presentation is uncommon.

Answer 155

**Contiguous spread** Contiguous spread is a feature of Hodgkin’s disease, compared with non-contiguous spread in non-Hodgkin’s disease. Other differences include greater thoracic involvement and less abdominal involvement in Hodgkin’s disease.

Answer 156

**Intercostal schwannoma** The description is of a posterior mediastinal lesion obscuring part of the descending thoracic aorta. The other lesions are anterior mediastinal apart from hilar lymphadenopathy, which is hilar/middle mediastinal.

Answer 157

**Spinnaker/thymic sail sign** Plain radiographic signs of pneumomediastinum include the Spinnaker or thymic sail sign in children, streaky lucencies in the thoracic inlet, and tubular artery sign, where air outlines the major arteries.

Answer 158

**Thick wall** Bronchogenic cyst is the most common intrathoracic foregut duplication cyst. It could have all the above features, but in a mediastinal location, the cyst walls are usually thin. Thick-walled cysts are more likely to be oesophageal.

Answer 159

**Pulmonary contusion** Pulmonary contusion is the commonest manifestation of blunt trauma and indicates trauma to alveoli with alveolar haemorrhage without significant alveolar disruption. Whilst plain film changes may not be apparent for up to six hours, CT will demonstrate changes almost immediately post-trauma and signs of resolution can be seen as early as 48 hours. If unresolved, it may progress to ARDS.

Answer 160

**Fibrosing mediastinitis** Fibrosing mediastinitis is a rare condition which has two forms: focal (usually secondary to tuberculosis or histoplasmosis) or diffuse (often idiopathic). When associated with tuberculosis, it is thought to be secondary to rupture of lymph nodes in the neck or mediastinum. Calcification is seen in 63% of cases, but the mass may be difficult to differentiate from malignant conditions when calcification is not present. Symptoms and signs are due to compression/obstruction of mediastinal structures. Small-cell carcinoma and lymphoma can produce middle mediastinal masses, but calcification is rare, unless in treated lymphoma when progressive symptoms would be unlikely. Malignant teratomas are typically anterior mediastinal masses which have well-defined lobulated margins, and usually do not calcify.

Answer 161

**Water-soluble contrast swallow** Oesophageal rupture is the most likely diagnosis. CT may be able to elicit suspicious signs, such as mediastinal gas, oesophageal thickening and pleural effusion, but cannot make a definitive diagnosis. A contrast swallow is best in confirming the diagnosis, but barium should not be used due to its potential to cause a severe inflammatory reaction and worsening mediastinitis.

Answer 162

**Aortic Rupture** Aortic injury is usually fatal, though some patients survive to reach hospital. A chest radiograph may show a variety of features including deviation of the trachea and oesophagus (position of nasogastric tube) to the right, depression of the left main bronchus, apical pleural cap and left pleural effusion. The presence of a mediastinal haematoma following trauma is more likely due to azygos or hemiazygos vein injury or possibly internal mammary or intercostal artery injury. Superior vena caval injury tends to cause right-sided mediastinal and lung changes. Bronchial rupture may be accompanied by vascular injury but would tend to present with pneumomediastinum and pneumothorax with or without collapsed lung.

Answer 163

**Extramedullary haematopoiesis** Extramedullary haematopoiesis occurs in conditions where there is prolonged anaemia. This can occur in the spleen, liver, lymph nodes, adrenals and many other sites. In the mediastinum it produces a rounded/lobulated, paraspinal soft-tissue mass, usually between T8 and T12. Unlike other causes of paraspinal masses, there is usually no pain or bone erosion. Bronchogenic cysts are of fluid density. Bochdalek’s hernia can present in adults as a paravertebral mass, which is usually asymptomatic and contains fat as well as abdominal organs (bowel, kidney or spleen). It is usually left sided. Tuberculous abscesses are usually associated with bone destruction. Neurogenic tumours are rounded/ovoid and may extend through the intervertebral foramen into the spinal canal and/or produce bone erosion.

Answer 164

**Liposarcoma** Liposarcoma is an uncommon tumour in the thorax. It contains variable amounts of fat, with soft-tissue components that may enhance following intravenous contrast. Calcification may occur within these lesions. Lipomas are more common and occur anywhere within the mediastinum. Hamartomas usually present as soft-tissue nodules within the peripheral lung and classically show popcorn calcification. They may contain fat. Neurofibromas present as paravertebral masses, often extending into the intervertebral canal, and may have fatty attenuation due to the presence of myelin. Thymolipomas occur in the anterior mediastinum and are found in young adults.

Answer 165

**Thyroid goitre** Thyroid goitres extend into the mediastinum in 3–17% of cases. Tracheal displacement may occur due to any adjacent enlarging mass, but narrowing is specific for thyroid lesions, especially goitre. Calcification is common. Teratomas tend to arise more often in the anterior mediastinum, though they may involve the superior mediastinum by extension. Thymomas may arise in the superior or anterior mediastinum. Either of these may show calcification. Lymph node masses tend to calcify only after treatment, such as radiotherapy for lymphoma.

Answer 166

**Predominantly posterior mediastinal lymph node involvement** Mediastinal nodal involvement is generally more suggestive of Hodgkin’s disease, but disease is usually seen in the middle and anterior mediastinum. Posterior mediastinal involvement, with little or no anterior or middle mediastinal involvement, suggests non-Hodgkin’s lymphoma as a more likely diagnosis. Calcification can occur in either condition, nearly always post-therapy. The size of the lymph node masses is not discriminatory.

Answer 167

**Calcification** A definite diagnosis as to whether a teratoma is benign cannot be made on radiological features. Features suggestive of a benign nature are a rounded lesion, projection from one side of the mediastinum, and calcification (especially if in the form of a tooth). A fat–fluid level is characteristic of a benign lesion but is rare. Features more suggestive of malignancy are lobulated margins, invasion into adjacent structures (may cause pleural or pericardial effusions), and projection from both sides of the mediastinum.

Answer 168

**Endobronchial tuberculosis** The CT findings describe the ‘tree-in-bud’ pattern, which results from centrilobular bronchiolar dilatation and filling by mucus, pus, or fluid that resembles a budding tree. It is usually most pronounced in the lung periphery. All of the options provided are differentials for ‘tree-in-bud’, although infective causes are most common, classically endobronchial spread of active TB. The patient in this case is also at risk of invasive aspergillosis, although typically the ‘tree-in-bud’ pattern occurs in combination with consolidation accompanied by a halo of GGO. Obliterative bronchiolitis occurs in bone marrow transplantation in the setting of chronic graft-versus-host disease. The most sensitive CT finding in this condition is air-trapping on expiratory CT. Diffuse pan-bronchiolitis is of unknown cause but occurs almost exclusively in Eastern Asia. Primary pulmonary lymphoma is also a rare cause of ‘tree-in-bud’. Other potential differentials of this pattern include cytomegalovirus infection, cystic fibrosis, aspiration, connective tissue disease, and tumour emboli.

Answer 169

**Air-trapping** Air-trapping is an indirect finding of small airway narrowing/obliteration and is the most common and identifying imaging feature of constrictive bronchiolitis. Air-trapping is accentuated on expiratory scans.

Answer 170

**Systemic amphotericin** Post-transplant complications * Infections – most common cause of death (Aspergillus – very high mortality) * Rejection – radiologically similar to pulmonary oedema, endomyocardial biopsy * Accelerated atherosclerosis of the graft * Post-transplant malignancy – Skin carcinoma, adenocarcinoma of the lung or GI tract, Kaposi sarcoma, Lymphoproliferative disorder (Leukaemia, Lymphoma)

Answer 171

**Drug toxicity** Post-transplant pulmonary complications may develop in up to 40–60% of patients. 1. Neutropenia – First two weeks, most common. 2. Angio-invasive Aspergillosis – first 2-3 weeks, multiple GGO +/- cavities and peribronchiolar consolidation 3. Lyphoid Interstitial Pneumonia (LIP) – >3 months, chronic GVH 4. CMV Pneumonia – any time in the first 100 days. Multiple GGO or consolidation but not reticulation 5. Drug Toxicity – Neutropenic phase, combination of groundglass and reticular changes 6. Pulmonary oedema – Neutropenic Phase ground glass and reticular, also pleural effusion.

Answer 172

Acute rejection is the most likely cause as it typically presents with fever, dyspnea, and radiological changes similar to those described. Reperfusion edema typically occurs immediately post-transplantation, while anastomotic dehiscence would present differently. PCP infection usually occurs later than 8 days post-transplant.

Answer 173

**Pulmonary laceration** occurs following trauma disrupting the lung parenchyma. The typical appearance is of a rounded cavity containing blood and/or air. On plain films, consolidation due to contusion often obscures the laceration. The laceration appears as a rounded/ovoid opacity with a pseudocapsule of compressed lung (2–3mm), and may be fully opacified, be filled with air or have an air–fluid level. Complications are uncommon and include abscess (causes fever), bronchopleural fistula (causes pneumothorax) and progression. Bronchogenic cysts could present as an incidental finding after trauma but are usually mediastinal in location. The less common intrapulmonary bronchogenic cysts may cavitate. Pulmonary infarcts may present post-trauma due to immobilization and other risk factors causing pulmonary embolus, but these do not usually cavitate.

Answer 174

**Morgagni’**s **hernia** is due to a developmental defect anteromedially in the diaphragm between the septum transversum and left (10%) or right (90%) costal margins. They are usually asymptomatic but can produce pain. They are usually small and present in older children or adults. A Bochdalek hernia is a posterolateral developmental defect. It tends to be large, is more common on the left and presents in infancy. Rolling hiatus hernia is herniation of the stomach through the oesophageal hiatus alongside the oesophagus. A septum transversum defect is a defect in the central tendon.

Answer 175

**Chronic renal failure** is the most likely cause as the appearances are suggestive of ‘metastatic’ pulmonary nodular calcification secondary to chronic renal failure. The upper lobe distribution is due to the relative alkalinity of the upper lobes, caused by the higher ventilation-to-perfusion ratio. It is often associated with calcification of chest wall vessels. Varicella produces multiple calcified nodules of 1–3mm after the acute episode has resolved. Patients with tuberculosis or histoplasmosis, where calcified nodules are seen, have 2–5mm, well-defined nodules, and most have calcified lymphadenopathy. Talcosis characteristically produces 1mm, very-high density nodules.

Answer 176

**Macleod’s syndrome** (Swyer–James) syndrome is a result of acute bronchiolitis in childhood causing obliterative bronchiolitis. There is usually a history of recurrent infections. Chest radiographs show hyperlucent lung with a small or normal-sized hemithorax. High-resolution CT shows reduced vascularity and attenuation of lung with air trapping. Congenital lobar emphysema presents in the first 6 months of life with respiratory distress and a hyperlucent, overexpanded lobe (usually left upper) on the chest radiograph. Poland’s syndrome is an absence of part of the pectoralis major muscle, which causes apparent hyperlucent lung, though the lung is normal. Hypogenetic lung syndrome is usually asymptomatic and causes reduced volume of lung with reduced lucency.

Answer 177

**Rheumatoid arthritis** is characterized by erosion of the lateral ends of the clavicle, seen in several conditions including rheumatoid arthritis, hyperparathyroidism, and cleidocranial dysostosis. The associated rib notching and loss of the space between the humeral head and acromion (due to wasting/rupture of supraspinatus) are typically seen with rheumatoid arthritis. Clavicle erosions are not features of neurofibromatosis or osteoarthritis.

Answer 178

**Amiodarone pulmonary disease** occurs after 1–12 months of treatment. Features are of alveolar and interstitial infiltrates and high-density areas of consolidation (iodine attenuation). Heart failure usually gives a ‘bat-wing’ distribution of consolidation with increased heart size and vascular congestion, and often cyanosis. Sarcoidosis may produce reticulonodular changes, which coalesce to form areas of consolidation. Acute extr

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