Most host defense mechanisms in the airways exist at what levels
Pharynx, trachea, central bronchi
Once the organisms penetrate the lung parenchyma, what is or are activated? Cellular immunity? Humoral? Or both?
Both
3 potential routes responsible for producing pneumonia
Via the tracheobronchial tree, pulmonary vasculature or via direct spread from infection in the mediastinum, chest wall or upper abdomen
3 radiographic patterns of pneumonia
Lobar pneumonia, lobular or bronchopneumonia, atypical pneumonia
Typical of pneumococcal pulmonary infection. In this pattern of disease, the inflammatory exudate begins within the distal airspaces
Lobar pneumonia
Inflammatory process (pathophysiology) in lobar pneumonia
Spreads via the pores of Kohn and canals of Lambert to produce nonsegmental consolidation
Most common pattern of disease and is most typical of staphylococcal pneumonia
Bronchopneumonia
Radiographically, at appears as multifocal opacities that are roughly lobular in configuration produce a “patchwork quilt” appearance because of the interspersion of normal and diseased lobules
Bronchopneumonia
In the early stages of bronchopneumonia, the inflammation is centered primarily
In and around lobular bronchi
Pattern of pneumonia most often the result of viral and mycoplasma pulmonary infection, there is inflammatory thickening of bronchiolar and alveolar walls and pulmonary interstitium
Atypical pneumonia
Segmental and subsegmental atelectasis from small airways obstruction is common in this pattern of pneumonia
Atypical pneumonia
At what part of the lungs is severely affected by hematogeneous spread of infection
Lung bases
Patterns of disease in strep pneumoniae, legionella, klebsiella and haemophilis influenzae
Lobar/sublobar consolidation and air bronchograms
Patterns of disease in staph aureus, pseudomonas, e. Coli, anaerobes, actinomyces
Lobular/patchy consolidation, absence of air bronchograms, bronchial wall thickening
Pattern of disease in mycoplasma and chlamydia
Ill-defined nodular/patchy opacities, reticular opacities, bronchial wall thickening
Pattern of disease in nocardia
Nodules/masses and consolidation
Pathogen common in elderly, alcoholics, compromised hosts, sickle disease and patients who had undergone splenectomy
Streptococcus pneumonia
Pathogen of pneumonia that tends to begin in the lower lobes or the posterior segments of upper lobes
Pneumococcal pneumonia
2 forms of tb that are recognized clinically and radiographically
Primary tb and postprimary or reactivation disease
Tuberculosis differs from normal response to bacterial organism, in that it involves
Cell-mediated immunity (delayed hypersensitivity)
typical radiographic appearance of acute pneumococcal pneumonia
lobar consolidation
cavitation in pneumococcal pneumonia is rare, with the exception of infections caused by what serotype
serotype 3
important cause of nosocomial pneumonia, and typically affects debilitated patients
staphylococcus aureus
pathogen responsible for hematogeneous spread to the lungs in patients with endocarditis or indwelling catheters and IV drug users
staph aureus
bilateral bronchopneumonia which may be complicated with abscess are usually seen in what pathogen
staph aureus
pneumatoceles are common in what pathogen
staph aureus
pneumatoceles may be distinguished from abscesses by what features
thin walls, rapid change in size, tendency to develop during late phase of staph aureus infection
pleural effusion is common in staph pneumonia or uncommon?
common, that may rapidly result in epyema
gram neg bacteria that are most often responsible for pneumonia
enterobacteriaceae family (e.coli, klebsiella, proteus, serratia), pseudomonas, haemophilus influenzae, legionella
gram neg pneumonia that occurs predominantly in older alcoholic men and debilitated hospitalized patients. appears as a homogeneous lobar opacification containing air bronchograms
Klebsiella pneumoniae
These features, when present, can held distinguish klebsiella pneumonia from pneumococcal pneumonia
- volume of involved lobe may be increased by the exuberant inflammatory exudate, producing a bulging interlobar fissure
- abscess may develop, with cavity formation, which is uncommon with pneumococcal pneumonia
- incidence of pleural effusion and empyema is higher
- pulmonary gangrene, however, rare
most common pathogen of pneumonia in patients with COPD, alcoholism, DM and those with an anatomic functional splenectomy
Haemophilus influenzae
Most often cause bronchitis, atho it may extend to produce bilateral lower lobe bronchopneumonia
Haemophilus influenzae
pneumonia that most often affects debilitated patients, particularly those requiring mech ventilation
pseudomonas aeruginosa
presents as patchy opacities with abscess formation, which mimic staphylococcal pneumonia, are common when the infection reaches the lung via the tracheobronchial tree. pleural effusion are common and are usually small
pseudomonas aeruginosa
gram neg bacillus commonly found in air conditioning and humidifier systems
legionella pneumonia
characteristic radiographic pattern is airspace opacification, which is initially peripheral and sublobar. In some patients, the airspace opacities appear as round pneumonia. The infection progresses to lobar or multilobar involvement despite the initiation of antibiotic therapy. At peak of disease, parenchymal involvement is usually bilateral
legionella pneumonia
the radiographic resolution of this type of gram neg pneumonia is often prolonged and lag behind symptomatic improvement
legionella pneumonia
the majority of anaerobic lung infections arise from
aspiration of infected oropharyngeal contents
most common organisms in aspirated infected oropharyngeal contents causing pneumonia are
gram neg bacilli bacteroides and fusobacterium
true or false, all anaerobic pulmonary infections produce a similar radiographic appearance
true
when aspiration occurs in the supine position, what segments are predominantly involved
posterior segments of upper lobes and superior segments of lower lobes
aspiration in erect position leads to involvement of what segments
lower lobes
typical radiographic appearance of anaerobic pulmonary infections include
peripheral lobular and segmental airspace opacities, cavitation with areas of consolidation, discrete lung abscesses, hilar and/or mediastinal lymph node enlargement, empyema with or without bronchopleural fistula formation
an anaerobic gram positive filamentous bacterium that is a normal inhabitant of the human oropharynx. it causes disease when it gains access to devitalized or infected tissues that facilitate its growth. most commonly follows dental extractions, manifesting as mandibular osteomyelitis or soft tissue abscess. lung findings include nonsegmental airspace opacities in the periphery of the lower lobes. In some cases, the infection manifest as mass-like opacity, mimicking a lung cancer
actinomycosis
true or false: thoracic actinomycosis is characterized by its ability to spread to contiguous tissues without regard for normal anatomic barriers
true
most common atypical pneumonia and account for 10% to 15% of all community-acquired pneumonia
mycoplasma
pattern of mycoplasma pneumonia
unilateral, tends to involve lower lobes, fine reticular pattern, may progress to patchy segmental ground glass or airspace opacities which may coalesce to produce lobar consolidation
Granulomas are usually well formed by what weeks, coinciding with the development of delayed hypersensitivity
1-3 weeks
Consists of a calcified parenchymal focus (ghon lesion) and a nodal calcification
Ranke complex
Discrete nodular opacities that may develop in primary TB but are more common in postprimary tb
Tuberculomas
Tuberculous pleural effusion is made by demonstrating granulomas on parietal pleural biopsy or detecting _____ in pleural fluid samples
Elevated adenosine deaminase
Detection of necrotic lymph node enlargement in a patient with TB suggests active or inactive disease
Active disease
Hilar enlargement in tb are usually unilateral or bilateral?
Unilateral
During the primary tuberculous infection, there is homogeneous dissemination of the organism to regions with
High partial pressure of oxygen; these include the lung apices, renal medullae and bone marrow
Reactivation tb tends to occur at what lung regions
Apical and posterior segments of upper lobes and the superior segments of the lower lobes
Important radiographic feature of postprimary infection and usually indicates active and transmissible disease
Cavitation
Erosion of a cavitary focus into a branch of pulmonary artery can produce an aneurysm called
Rasmussen aneurysm
Parenchymal healing of tb are associated with
Fibrosis, bronchiectasis and volume loss (cicatrizing atelectasis) in the upper lobes
Late complications of pulmonary TB
Interstitial fibrosis, which can cause pulmonary insufficiency and secondary pulmonary arterial hypertension, bronchiectasis, mycetoma formation, erosion of a calcified peribronchial lymph node (broncholith), bronchostenosis
Size of pulmonary nodules in miliary tb
2-3 mm
Most common organisms responsible for pulmonary disease caused by atypical mycobacterial infection are
Mycobacterium avium intracellulare or mycobacterium kansasii
Radiographic features of the most common form of this pulmonary infection are often indistinguishable from tb, with chronic fibrocavitary opacities involving the upper lobes. While cavitation is common, PE, lymph node enlargement and miliary spread are distinctly unusual
Pulmonary mycobacterium avium-intracellulare infection
Second pattern of disease with MAI in middle-aged and elderly women presents with
Small centrilobular nodules and bronchiectasis, often in middle lobe and lingular distribution
Third form of MAI infection reflects a hypersensitivity reaction to inhaled MAI in hot water systems and has been termed “hot-tub” lung. Imaging features include
Hypersensitivity pneumonitis with centrilobular ground glass nodules and ground glass opacities
Standard treatment for pulmonary MAI
Combination of 3 antibiotics for a minimum of one year
Pattern of viral pneumonia
Nonspecific, demonstrates a pattern of bronchopneumonia or reticulonodular opacities
Resolution of viral pneumonia is usually complete, but permanent sequelae may be seen including
Bronchiectasis, constrictive bronchiolitis (which may produce a unilateral hyperlucent lung or Swyer-James syndrome), and pulmonary fibrosis
In most cases of influenza, disease is confined to the
Upper respiratory tract
In elderly persons, those with underlying cardiopulmonary disease or immunocompromised, and in pregnant women, influenza may cause
Severe hemorrhagic pneumonia
In adults with influenza pneumonia, there is often what pattern of opacities
bilateral lower lobe patchy airspace opacification, ground-glass or airspace opacities with centrilobular nodules
Bacterial superinfection with what organisms contributes to a fulminating course that may to death in influenza pneumonia
Streptococcus or staphylococcus organisms
Common causes of epidemic viral pneumonia in children. Presents as patchy airspace opacities, bronchial wall thickening and centrilobular nodules and tree-in-bud opacities
Respiratory syncytial virus and parainfluenza
Patients on immunosuppresive therapy or with lymphoma are at greatest risk. Presents as diffuse bilateral ill-defined nodular opacities 5-10mm in diameter. These opacities usually resolve completely, altho in some patients they involute and calcify to produce innumerable small (2-3 mm) calcified nodules
Varicella zoster
Frequent cause of upper and occasionally lower respiratory tract infection. Hyperinflation and bronchopneumonia accompanied by lobar atelectasis are most frequent radiographic manifestations, however in children, it may present as lobar or segmental consolidation
Adenovirus
endemic fungi that are endemic and most commonly infect normal hosts
Histoplasma capsulatum, Coccidiodes immitis, and Blastomyces dematidis
opportunistic fungal pathogens in immunocompromised hosts
aspergillus, candida, cryptococcus, mucormycosis (zygomycosis)
in all cases, fungi elicit what type of reaction
necrotizing granulomatous reaction
medications used in fungal infection
triazoles (fluconazole, intraconazole, voriconazole, posaconazole), lipid-laden amphotericin B and endocardins (caspofungin)
radiographic finding tha may be the only indication of prior histoplasmosis infection
multiple well defined calcified nodules less than 1 cm in size, with or without calcified hilar or mediastinal lymph nodes
histoplasmoma size
<3cm
histoplasmomas are commonly seen in what lobe of the lungs
lower lobes
imaging findings in primary TB
mediastinal/hilar lymph node enlargement (necrotic), segmental/lobar consolidation, PE, military opacities
imaging findings in postprimary TB
consolidation with cavitation, centilobular nodules/tree-in-bud densities
imaging findings in inactive TB
calcified nodules +/- lymph nodes, fibronodular changes in upper lobes
imaging findings in fibrocavitary form of non-tubercuous mycobacteria
single/multiple cavities, centrilobular nodules, tree-in-bud opacities
imaging findings in nondular bronchiectatic form od non-tuberculous mycobacteria
cylindrical bronchiectasis (esp ML/lingula), centrilobular nodules, patchy consolidation
imaging findings in allergic (“hot-tub lung”) forn of nontuberculous mycobacteria
centrilobular ground glass nodules, GGO, air trapping in expiratory CT
asymptomatic blood-borne dissemination of H.capsulatum is common, as judged by the frequency of what finding in the spleen in residents of endemic areas
calcified splenic granulomas
fungal infection endemic to southwestern US nd San Joaquin Valley of California
Coccidioidomycosis
caused by B.dermatitidis, is a chronic systemic disease primarily affecting the lungs and skin
blastomycosis
these species are responsible for a spectrum of pulmonary diseases in humans. this includes aspergilloma or mycetoma formation within preexisting cavities, semi-invasive (chronic necrotizing) aspergillosis in patients with mildly impaired immunity, invasive pulmonary aspergillosis in neutropenic lymphoma or leukemia patient, and allergic bronchopulmonary aspergillosis in hyperimmune patient
aspergillus
is a ball hypahe, mucus, and cellular debris that colonizes a pre-existing bulla or a parenchymal cavity created by some other pathogen or destructive process such as post-primary TB
aspergilloma
in general, parasitic diseases of the thorax are manifested by what types of invasion/spread of disease
direct invasion of lungs and pleura, or less commonly, a hypersensitivity reaction
Amoebiasis is usually confined to the GI tract and liver. If the infection remains confined to the subphrenic space, it may result into
right PE and basilar atelectasis, from local diaphragmatic inflammation
the most common method of pleuropulmonary involvement by amebiasis is by
direct intrathoracic extension of infection from a hepatic abscess
the cause of most cases of human hydatid disease
Echinococcus granulosus
this disease is endemic in sheep-raising areas. Dogs, coyotes and wolves are the usual definitive hosts with sheep, goats and cattle acting as intermediate hosts
Hydatic disease (echinococcosis)
three layers of pulmonary echinococcal cysts
exocyst (chitinous layer)- protective membrane
inner endocyst- daughter cysts
surrounding capsule of compressed fibrotic lung known as pericyst
pulmonary echinococcal cysts are well-circumscribed, spherical soft tissue masses. In distinction to hepatic cysts, lung cysts do not have
calcified walls
echinococcal cysts range in size from __ to __ cm, with predilection to the
1-20cm, lower lobes and the right side
if the pericyst of echinococcus ruptures, a thin crescent of air will be seen around the periphery of the cyst, producing the ___ sign
meniscus or crescent sign
if the cyst wall of echinococcus may be seen crumpled and floating within an uncollapsed pericyst, it produces the pathognomonic sign called
sign of the camalote or water lily sign
result from infection with the lung fluke paragonimus westermani
paragonimiasis
lung fluke paragonimus are found predominantly in what part of the world, acquired by eating raw crabs or snails
eastern asia
schistosomiasis is caused by three blood flukes, namely
schistosoma mansoni, japonicum and haematobium
pathophysiology of schistosomiasis
larvae penetrate the skin or oropharyngeal mucosa, travel via the venous circulation to pulmonary capillaries, an acute allergic response in the lungs may develop, presenting as transient airspace opacities (eosinophilic pneumonia), larvae then pass thru the pulmonary capillaries into the systemic circulation, eventually migrate to mesenteric venules (japonicum and mansoni) or bladder venules (haematobium). mature flukes produce ova which may embolize the lungs, where they implant in and around small pulmonary arterioles, induces granulomatous inflammation and fibrosis, leading to obliterative arteriolitis, resulting in pulmonary hypertension and cor pulmonale
caused by a nematode Dirofilaria immitis (dog heartworm) presents as an asymptomatic subpleural solitary pulmonary nodule that represents an inflammatory reaction surrounding a dead worm that has embolized from a peripheral vein to lodge in a peripheral pulmonary artery branch
Dirofilariasis
most common complication of pneumonia
parapneumonic effusion
type of effusion with low pH, elevated LDH and protein
exudative
when an empyema collection extends to create an infected subcutaneous collection in the chest wall, it is termed
empyema necessitatis
organisms most often associated with empyema necessitatis are
TB, A. israelii, nocardiosis, fungus and staphylococcal infection
most often the result of aspiration of mouth anaerobes with or without aerobes, and is seen 10-14 days following aspiration
lung abscess
some lung abscesses develop as an embolic complication of
septic thrombophlebitis or tricuspid endocarditis
appears as nodules or masses typically with central necrosis with or without air-fluid levels, and develop in the gravity dependent portions of the lungs (posterior upper lobes, superior segment, and subpleural regions of the lower lobes)
abscess
rare complication of severe pulmonary infection when a portion of lung is sloughed. occurs when there is thrombosis of pulmonary vessels
pulmonary gangrene
pulmonary gangrene can be seen in severe bacterial pneumonia but is more closely associated with
invasive pulmonary fungal infection
imaging findings of pulmonary gangrene
nodule or mass within a cavity with a crescent of air surrounding the sloughed portion of lung
rare complication of pulmonary infection or infective endocarditis. presents as lung nodule or mass adjacent to a hilar vessel in a patient with endocarditis or pneumonia
mycotic aneurysm
uncommon postinfectious form of constrictive bronchiolitis that typically results from a sever viral or mycoplasma infection in infancy or childhood. typical radiologic findings include a hyperlucent lung with normal or small volume, attenuated vasculature, air trapping and occasionally proximal bronchiectasis
Swyer-James syndrome
bronchial stenosis are most often associated with
endobronchial TB or fungal infections such as histoplasmosis
reflects presence of an endobronchial calcified nodule, most often seen as a result of erosion of a calcified peribronchial lymph node resulting from histoplasmosis or TB
broncholithiasis
appears radiologically as mediastinal widening with calcifications. focal mediastinal mass can also be seen. CT typically demonstrates either a localized calcified right paratracheal or subcarinal mass or soft tissue infiltration of the middle mediastinum with compression or obliteration of structures
Fibrosing mediastinitis (sclerosing mediastinitis)
common pulmonary infection in pre-engraftment phase (0-30 days) of hematopoietic stem cell transplant recipients
aspergillosis, bacterial infection, RSV pneumonia
common pulmonary infection in early post-transplantation phase (30-100 days) of hematopoietic stem cell transplant recipients
CMV, pneumocystis jiroveci, aspergillosis
common pulmonary infection in late post-transplantation phase (>100days) of hematopoietic stem cell transplant recipients
Bacterial, aspergillosis, viral (adenovirus, RSV, varicella zoster, parainfluenza)
most common cause of pneumonia in ICC host
bacteria
most common organisms causing pneumonia in HIV patients are
S. pneumoniae, H. influenzae, S. aureus, E.coli and P. aeruginosa
most common bacterial pathogens in the non-HIV ICC patients are
S. aureus and gram-negative aerobes including Klebsiella, proteus, E. coli, Pseudomonas, enterobacter and serratia
renal transplant recipients and patients on high-dose corticosteroids are at increased risk of pneumonia caused by
L. pneumophila and legionella micdadei (Pittsburgh agen),
usually opportunistic infection in patients on immunosuppressive therapy, those with lymphoma or leukemia and patients with alveolar proteinosis
nocardia
treatment for nocardiosis
sulfonamides
in early stages of AIDS (CD4 count >200 cells/mm3), what pattern is seen if afflicted with TB
postprimary pattern of upper lobe fibrocavitary disease indistinguishable from that seen in the immunocompetent patient
later in the course of AIDS (CD4 counts 50 to 200 cells/mm3), the radiographic features most often associated with primary TB disease are
lobar consolidation, mediastinal and hilar lymphadenopathy and PE
In advanced AIDS (CD4 <50 cells/mm3), the radiographic findings of TB are
atypical and are characterized by diffuse reticular or nodular (military) opacities
most common nontuberculous mycobacterial infection in AIDS patients
Mycobacterium avium intracellulare
common cause of viral pneumonia in patients with impared cell-mediated immunity, specifically renal transplant recipients and lymphoma. it is however uncommon cause of pneumonia in AIDS population
CMV
usually occurs in severely immunocompromised patients with neutropenia, most commonly those with leukemia or those receiving chemotherapy or corticosteroids. occurs less frequently in AIDS patients, usually in terminal stage of disease
aspergillosis
these fungal infection tends to invade blood vessels, causing infarction
aspergilllosis
relatively specific CT finding for invasive aspergillosis in a neutropenic patient
demonstration of zone of relative decreased attenuation surrounding a dense, mass-like opacity termed “halo sign”
halo in “halo sign” of aspergillosis represent
edema and hemorrhage where an air crescent will develop, separating the region of infected, necrotic lung from normal parenchyma
budding yeast commonly found in soil and bird droppings. most common cause of fungal infection in AIDS but can affect any IC patient
Cryptococcosis
most serious complication of cryptococcosis
meningitis
unusual cause of pneumonia in IC patient. most susceptible are patients with severe neutropenia caused by lymphoma or leukemia in the late stages of disease
candidiasis
this pulmonary infection is commonly accompanied with paranasal sinus infection, which may extend to involve the brain or meninges. chest radiographic appearances include a solitary nodule or mass or focal airspace opacity which may cavitate
mucormycosis (zygomycosis)
most common AIDS defining opportunistic infection
pneumocystits jiroveci pneumonia
PJP presents as
fine reticular or ground glass pattern, particularly in the parahilar regions
four clinicopathologic forms of toxoplasmosis
congenital, ocular, lymphatic and generalized
