Respiratory Pathology

Question 0

Describe Aerogenous spread of invasion to the lungs

Answer 0

Infection reaches the lung as inhaled droplets or larger food particles or fluid. As particle size decreases, increased proportion of particles will pass down the respiratory tract. The bronchiolar-alveolar junction is vulnerable to damage as the total air space area suddenly increases at this point so particles can settle by gravity.

Question 1

What are the varying defence mechanisms of the zones of the respiratory system?

Answer 1

Conducting - mucus and mucocilliary clearance, antibodies and lyzozyme.
Transitional (bronchioles) - clara cells, antibodies and lyzozyme
Exchange (alveoli) - macrophages, surfactant, antibodies.

Question 2

Describe Haematogenous Spread of infection to the lungs

Answer 2

The pulmonary capillary bed is very large. Haematongenous lesions tend to localise in caudal lobes - but all lobes can be affected when challenge is high. There is no orientation in the airways.

Question 3

Describe Transcoelomic spread of infection to the Lungs

Answer 3

Infection via extension from pleura or mediastinum, or traumatic penetration from the chest wall (e.g bite), diaphragm, or oesophagus e.g foreign body.

Question 4

What is Haemoptysis?

Answer 4

Blood in the saliva or sputum.

Question 5

Describe Rhinitis and its causes.

Answer 5

Rhinitis and sinusitis often occur together. Rhinitis may be acute or chronic. Aetiologies are infectious, allergic, toxic or traumatic. Within respiratory epithelium are two non ciliated secretory cells, serous cells that secrete clear thin sero mucin and goblet cells that secrete thick opaque mucus.

Question 6

What is serous rhinitis?

Answer 6

The mildest form - serous cells increase secretion. Early stages of infectious disease, allergy or irritation.

Question 7

What is catarrhal rhinitis?

Answer 7

Goblet cells and mucous glands now contribute to the secretion. With chronicity there may be goblet cell hyperplasia. May contain white blood cells, exfoliated debris (mucupurulent.)

Question 8

What is purulent suppurative rhinitis?

Answer 8

This is thicker exudate with many more cells. It is dominated by neutrophils.

Question 9

What is fibrinous rhinitis?

Answer 9

There is an increase in vascular permeability which allows exudation of fibrinogen which coagulates to fibrin and forms a yellow mat on the affected surface. May be associated with severe underlying ulceration.

Question 10

Describe granulomatous Rhinitis?

Answer 10

It is macrophage dominated - either specific pathogens or chronic allergic reaction.

Question 11

Describe Chronic Rhinitis?

Answer 11

Failure to resolve acute rhinitis - chronic rhinitis is typically catarrhal or purulent. In chronic purulent rhinitis there is extensive fibrosis of the lamina propria, atrophy of nasal glands and squamous metaplasia in severe cases. Another feature seen is polypoid thickening of the inflamed nasal mucosa known as nasal polyps. - Round large multiple protuberances into the nasal meatus.

Question 12

What is Sinusitis?

Answer 12

Often as a sequel or associated with rhinitis. It can also be caused by dental or periodontal disease and penetration of infections from dehorning wounds and fractures of the facial bones. Purulent inflammation of the sinuses is likely to become chronic because of poor drainage.

Question 13

Describe Viruses that may cause Rhinitis

Answer 13

Common cause of infectious rhinitis - in some fairly specific for nasal mucosa - others cause rhinitis as part of respiratory or more generalised disease. Eg feline calicivirus, canine distemper, parainfluenza, infectious bovine rhinotracheitis, bovine adenovirus, inclusion body rhinitis (porine), swine influenza, equine rhinovirus.

Question 14

Describe Atrophic Rhinitis in pigs?

Answer 14

Causes atrophy of nasal turbinates and distortion and shorening of the snout. It is caused by co-infection of the nasal mucosa with bordetella bronchiseptica and a toxin producing strain of pasteurella multocida capsular type D. The bordetella appears to facilitate colonisation of nasal epithelium by the toxigenic pasteurella. There is experimental evidence that the toxin acts directly on bone cells of the nasal turbinates to cause bone loss.

Question 15

Describe Strangles in horses and its potential complications?

Answer 15

Haemolytic streptoocoocci - streptococcus equi, is pathogenic and causes strangles, characterised by suppurative rhinitis, pharyngitis and lymphadenitis of the lymph nodes of the head and neck that drain the URT. Lymph nodes often rupture and discharge pus. Complications can occur such as metastatic abscesses, (bastard strangles), retropharyngeal abscesses can rupture into guttoral pouches and cause chondroid formation, and purpura haemorrhagica can occur - an acute vasculitis - urticaria and extensive oedema of ventrum, head and distal limbs.

Question 16

What is Glanders?

Answer 16

Caused by burkholderia mallei. It exists in Eastern Europe and Asia. The rhinitis of glanders is characterised by multiple small nodules in the nasal mucosa composed of cores of neutrophils surrounded by a rim of macrophages and granulation tissue. there is fever and head/neck lymphadenitis.

Question 17

What is mycotic Rhintis?

Answer 17

Aspergillus fumigatus is the commonest cause in the dog - where is also involves the frontal sinus. Infection causes a chronic necrotising inflammation with friable containing necrotic tissue and fungal hyphae. These lesions can be aggressive causing destruction of turbinates and nasal septum.

Question 18

Describe another cause of mycotic rhinitis?

Answer 18

Cryptococcus neoformans causes a granulomatous rhinitis in cats. Formation of nodules or destructive masses which often result in facial swelling. In severe cases, extension from nasal cavity to involve skin and oral mucosa can occur.

Question 19

Describe Neoplasia of the Nasal cavity and sinuses

Answer 19

Generally rare entities - can arise from any of the tissues in the region e.g adenoma from glands/epithelium, sarcomas from cartilage, bone, connective tissue. Most are malignant and are usually secondarily infected hence distinguishing severe chronic inflammation and neoplasia can be difficult.

Question 20

Describe inflammation of the larynx and trachea

Answer 20

Acute inflammation of the airways passes through changes similar to those describe for acute rhinitis. Inflammatory disease involving pharynx, larynx and trachea areas are important because of the potential to obstruct airflow and to cause aspiration pneumonia. Trauma and foreign bodies can cause problems in this area as can masses in the surrounding area which obstruct the airway.

Question 21

What is laryngeal chondritis?

Answer 21

Cause uncertain but there appears to be a genetic predisposition in short-necked breeds such as texels or southdowns, although any breed can be affected. Causes chronic suppuration within the arytenoid cartilages of the larynx resulting in swelling and occlusion of the lumen.

Question 22

What is filaroides osleri?

Answer 22

A parasite which forms nodules around the tracheal bifurcation - submucosal nodules (up to 1cm diameter). Associated with a mild chronic inflammatory reaction when the parasites are alive - subsequently, when the parasites die, an intense foreign body reaction develops.

Question 23

What is tracheal collapse?

Answer 23

Malformations of the trachea that lead to tracheal collapse are important in the dog and occurs principally in miniature dog breeds, also in horses and cattle. The trachea is flattened dorsoventrally with a widened, flaccid dorsal tracheal membrane. Upon inspiration the flaccid membrane is sucked into the tracheal lumen causing obstruction.

Question 24

What is laryngeal paralysis?

Answer 24

Horses and occasionally dogs develop paralysis of the larynx. It is the most common cause of abnormal respiratory noise (roaring) in horses. It is usually a left sided hemiplegia in horses due to degeneration of the left recurrent laryngeal nerve. Neurogenic atrophy of the left cricoarytenoid muscle causes the left arytenoid cartilage to sag into the laryngeal lumen during inspiration.

Question 25

Describe Kennel Cough?

Answer 25

This is a common condition characterised pathologically by persistent tracheobronchial inflammation. There can be extension to serous/mucupurulent rhinitis or cranioventral bronchopneumonia. Tonsils and RPLNs are enlarged.

Question 26

What is chronic bronchitis?

Answer 26

Bronchial irritation and mucus hypersecretion causes a chronic intractable cough. necropsy findings are dominated by excess mucoid or mucopurulent exudate within the trachea and lower airways. The underlying bronchial mucosa is thickened, hyperaemic and oedematous - this is a consequence of increase in size and number of mucus glands, extensive infiltration of the lamina propria by inflammatory cells. Another important feature is smooth muscle hypertrophy in pulmonary arteries can result in pulmonary hypertension - cor pulmonale.

Question 27

What is bronchiectasis?

Answer 27

This is permanent saccular or cylindrical dilatation of bronchi as a result of the accumulation of exudate within the lumen and partial rupture of the bronchial walls. It usually occurs secondary to chronic bronchitis in which there is a weakening of the bronchial wall. It has a classical appearance characterised by sac like nodules in the lungs which are filled with purulent exudate. Cattle are particularly prone to the development of bronchiectasis due to the combination of complete lobular septation and lack of collateral ventilation.

Question 28

Describe inflammation of the bronchioles?

Answer 28

Bronchiolar epithelium is highly susceptible to injury due to the presence of clara cells which contain oxidases that can locally generate metabolites that are toxic, and the vulnerability to free radical damage. Bronchioles are much more prone to obstruct when inflamed than bronchi. Bronchiolitis can occur as follows: as an extension of bronchitis or concurrently with bronchitis and pneumonia. Can occur as a distinct entity e.g certain viral infections; pulmonary toxicity.

Question 29

Describe the structure of Alveoli and their response to injury.

Answer 29

Alveoli have a delicate structure, the type 1 pneumocytes are most susceptible to injury. Irreversible injury results in swelling and sloughing of these cells. As long as the underlying basement membrane remains intact, repair can proceed as a result of type II pneuomocyte division. In severe, diffuse forms of alveolar injury, this process can be so spectacular that the affected tissue can take on the appearance of a gland - alveolar epithelialisation.

Question 30

What is pneuomonia?

Answer 30

Pneumonia is inflammation that takes place in the alveoli and their walls. Pneumonias can be classified in many ways, such as bronchopneuomina suppurative or fibrinous. Bronchinterstitial, interstitial, granulomatous, embolic.

Question 31

Describe Bronchopneuomonia?

Answer 31

Inflammation focussed on bronchi, bronchioles and adjacent alveolar lumens. It originates and extends from terminal bronchioles. The most common types are bacterial and mycoplasma infections or aspiration. Suppurative bronchopneumonia will be characterised by neutrophils, cell debris and macrophages within the airway and alveolar lumens.

Question 32

What is fibrinous bronchopneumonias?

Answer 32

Generally more severe and can cause sudden death due to associated toxaemia. Sometimes also called lobar pneumonia due to involvement of entire lobes and pleural surface. Due to severity, less likely to resolve completely - fibrosis and adehsions.

Question 33

What is interstitial Pneumonia?

Answer 33

Inflammation that occurs primarily in alveolar walls rather than in alveolar spaces. Lesions in most cases result from blood-borne insult and the damage is often diffuse. Can also occur due to direct aerogenous injury to alveolar epithelial cells. Injury to alveoli may cause protein and fluid exudation and hyaline membrane formation.

Question 34

describe an example of Interstitial Pneumonia

Answer 34

Fog fever/acute bovine pulmonary emphysema and oedema - usually seen in adult beef cattle in the autumn and is associated with a change in pasture. Underlying pathogenesis is ingestion of L-tryptophan in the pasture which is metabolised to 3-methylindole > bloodstream > lungs.

Question 35

Describe another example of interstitial pneumonia?

Answer 35

Paraquat poisoning - in dogs and cats - depending on the dose - the lesions range from acute lesions (oedema, haemorrhage, hyaline membranes) - to chronic (fibroplasia of alveolar septae, replacement of alveolar cells with type II cells). Additional extrapulmonary lesions to note following paraquat intoxication are necrosis of the adrenal zona glomerulosa and renal tubular epithelium.

Question 36

What is Embolic Pneumonia?

Answer 36

Lung inflammation caused by haematogenous spread of infections into the lung. This type of pneumonia has no orientation around airways and can occur in any lung region but most often affects caudal lobes. The inflammation is oriented around pulmonary arterioles or alveolar capillaries.

Question 37

What is granulomatous pneumonia?

Answer 37

A reaction dominated by macrophages +/- giant cells and varying associated lymphocytes and neutrophils. Seen as multiple granulomas scattered throughout the lungs.

Question 38

Describe pulmonary abscesses

Answer 38

Commonly found post mortem they can be a consequence of: Septic emboli lodging in the pulmonary vessels Extension from severe focal suppurative bronchopneumonia Aspiration of foreign material Direct penetration.

Question 39

Describe the main types of Equine Pneumonias

Answer 39

Equine influenza: a mild Bronchointerstitial pneumonia. Often complicated by secondary bacterial infection. Equine viral rhinopneumonitis: mild bronchointerstitial pneumonia. Rhodococcus equi: Foals or immunosuppressed adults, causes severe bronchopneumonia. R equi is phagocytosed by alveolar macrophages but survives within them - suppurative bronchopneumonia and abscess formation.

Question 40

What is bovine shipping/transit fever?

Answer 40

Pasteurellosis can manifest as acute septicaemia or in less acute forms more organ specific pathology can occur. Predisposing factors such as stress can affect local and systemic immunity such that disease can occur from normal bacterial flora in the nasopharyngeal and oral regions.

Question 41

What is Enzootic Pneumonia?

Answer 41

Often initiated by viruses or mycoplasmas. Secondary bacterial involvement then causes the lesions to progress e.g A pyogenes. clinically usually relatively mild and typified by lesions of bronchointerstitial pneumonia.

Question 42

Describe infection with Tuberculosis in the bovine

Answer 42

M tuberculosis and M bovis are the principle pathogens. They reside primarily within macrophages and can result in characteristic granulomatous inflammation.. Cattle can be infected by inhalation of the organism. The initial focus of infection is at the portal of entry (lungs) plus involvement of regional lymph nodes. If the infection is not contained in the primary complex, the mycobacteria can disseminate via lymphatics to other organs and lymph nodes. This can allow the development of miliary tuberculosis i.e numerous small foci of infection in many organs.

Question 43

What is respiratory syncytial Virus?

Answer 43

Affects Bovines, usually associated with winter housing, characterised by cranioventral atelectasis and consolidation, interstitial emphysema more prominent in caudal lung lobes.

Question 44

Describe parainfluenza virus type 3

Answer 44

This is a paramyxo virus which can induce acute respiratory disease in a range of species e.g ruminants. It is an example of a disease which is often part of a multi - aetiology disease complex. PI3 replicates in the airway epithelial cells and results in an initial bronchitis > bronchiolitis extension into the alveoli.

Question 45

Describe Canine distemper Virus (CDV)

Answer 45

Although many organs can be affected by CDV, a relatively constant feature is the respiratory signs which occur in varying severity. A syndrome of catharral oculonasal discharge, pharyngitis, and bronchitis is common. Since one of the primary sites of action of this virus is lymphoid tissue, the resultant immunosuppression > predisposition to secondary bacterial infection.

Question 46

Describe Ovine Maedi visna virus

Answer 46

Lymphoid interstitial pneumonia - uncommon in sheep <2yo as lesions develop slowly. the lungs fail to collapse properly on opening the chest. The lungs are a mottled grey/tan colour, lesions can vary from irregular grey speckling to homogenous grey consolidation. The associated bronchial and mediastinal lymph nodes are often enlarged.

Question 47

Describe Pasteurellosis in sheep:

Answer 47

As with cattle, there are several syndromes which can be caused by infection with this agent. Usually occurs in lambs in late spring/early summer with pathology similar to that described for cattle.

Question 48

What is Porcine Reproductive and respiratory syndrome?

Answer 48

An infectious disease in swine that emerged recently - causes respiratory and reproductive failure - an influenza like illness often is observed in the lungs of affected piglets.

Question 49

What is porcine enzootic pneumonia?

Answer 49

Caused by mycoplasma hyponeumoniae typified by lesions of bronchopneumonia which may be suppurative or catarrhal. the characteristic gross feature is confluent consolidation of the cranioventral lung lobes.

Question 50

Describe pasteurellosis in pigs?

Answer 50

P.multicodia can cause a severe acute fibrinous pneumonia in pigs as described in ruminants however the most significant disease here is that caused by P. multocida secondary to underlying mycoplasma pneumonia. This results in chronic suppurative bronchopneumonia with abscessation and pleuritis.

Question 51

What is Enzootic Pneumonia?

Answer 51

A disease of young animals iin close contact - particularly calves, lambs and pigs.

Question 52

What is aspergillus fumigatus?

Answer 52

The cause of aspergillosis - significant in birds. Disease is usually initiated following inhalation of spores, the most likely source of which is mouldy feed and bedding. Immunodeficiency may contribute to colonisation with this organism. Gross lesions: multiple discrete grey/white nodules which develop around fungal colonies Blood vessels can become involved in the lesions > invasion, haemorrhage or thrombosis.

Question 53

Describe dictyocaulus infection

Answer 53

The lesions produced by dictyocaulus spp. vary depending on the susceptibility of the host and the number of iinvading parasites. Cattle and sheep are most suceptible when first exposed o contaminated pasture hence in endemic areas, disease is most often seen in animals <1 yo. The pathogenesis and pathology associated with the parasites in ruminants can be divided into several phases.

Question 54

Describe the phases of Dictyocaulus infection:

Answer 54

Penetration phase - larvae are in transit to the lungs - no pulmonary lesions apparent. Pre patent phase - larvae appear in alveoli, alveolitis bronchiolitis > bronchitis. They plug the airway resulting in collapse distal to the lesion. Patent phase: parasitic bronchitis due to the presence of large numbers of worms in the bronchi. Histologically there is a pronounced inflammatory infiltrate. Parasitic pneumonia: caused by aspiration of eggs and larvae into the alveoli provoking a foreign body type response.

Question 55

Describe the postpatent phase of Dictyocaulus infection

Answer 55

In most causes this is the recovery phase. Acute exacerbations of respiratory disease can occur during this phase as a result of either: I) alveolar epithelialisation (type II cells). Grossly evident as pink rubbery lungs. II) Superimposed bacterial infection e.g pasteurella.

Question 56

Describe Dictyocaulus Arnfieldi Infection in Donkeys and horses?

Answer 56

A common parasite of donkeys. The gross pathology is characterised by raised focal over-inflated areas in the caudal lung lobes. These lesions consist histologically of central parasites and associated chronic catharral bronchitis. There is hyperplastic bronchial epithelium and surrounding lymphoid infiltration.

Question 57

What is Muellerius?

Answer 57

Caused by M capillaris - a very common parasite of sheep and goats - even with large infestations, there is very rarely any clinical significance. Intermediate hosts are slugs and snails in which infective larvae can survive for many months. The parasite causes a multifocal interstitial pneumonia which is grossly evident as firm nodules scattered throughout the parenchyma most obviously in the dorsal regions of the caudal lung lobes.

Question 58

Describe Metastrongylus infestation

Answer 58

Parasites of the bronchi/bronchioles of pigs - The histological lesions are similar to those in dictyocaulus, i.e catharral and eosinophilic bronchiolitis and bronchitis - however the lesions seldom become as extensive as can occur in dictyocaulus infections.

Question 59

What is Aelurostrongylus?

Answer 59

Aelurostrongylus is a widespread cat lungworm - seen wherever the intermediate hose are found. Adults live in respiratory bronchioles and alveolar ducts. The gross lesions are evident as multifocal subpleural firm yellow nodules scattered throughout the parenchyma although they are more frequent at the periphery. Eggs and larvae cause a foreign body type reaction. Submucosal gland hypertrophy and smooth muscle hypertrophy in airway and vessel walls also occurs.

Question 60

Describe hydatid cysts

Answer 60

Th intermediate stage of echinococcus granulosus can be found in the lungs. They range in size up to 5-10cm diameter and although of little clinical significance, are important as a zoonosis and because of carcass condemnation.

Question 61

What is type 1 Hypersensitivity and describe an example

Answer 61

Feline asthma/allergic bronchitis - inflammation usually dominated by eosinophils and some affected cats also have circulating eosinophilia. Causes a recurrent cough/ dyspnoea associated with Bronchoconstriction. Thought to relate to type 1 hypersensitivity to inhaled allergens.

Question 62

Describe a type 1 hypersensitivity - (PIE)

Answer 62

Pulmonary infiltration with eosinophilia - a group of small animal diseases in which there is a predominance of eosinophils in the airways. It is generally considered that there is underlying hypersensitivity to allergens.

Question 63

Describe Type III hypersensitivity reaction Extrinsic allergic alveolitis.

Answer 63

This condition arises due to repeated inhalation of spores of thermophilic actinomycetes in mouldy hay. Hence it is a disease primarily of housed animals in winter. The spores can penetrate to the level of terminal bronchioles and alveoli throughout the lung. The pathogenesis results from a type III hypersensitivity reaction to the inhaled fungal spores.

Question 64

What is diffuse fibrosing alveolitis/atypical interstitial pneumonia

Answer 64

a catch all phrase for end stage of a number of different diseases including EAA, reinfection syndrome and fog fever. May show some similarities terminally - progression from an acute exudative phase through a proliferative phase to a final irreversible stage of fibrosis.

Question 65

Describe the pathogenesis of COPD.

Answer 65

Chronic obstructive pulmonary disease - characterised by chronic coughing and poor performance. Severe cases may show respiratory distress. The pathogenesis involves sensitivity of the airways to environmental allergens - type III hypersensitivity. Grossly, affected lungs are often surprisingly unremarkable except in extreme causes which alveolar emphysema may be evident.

Question 66

What is aspiration Pneumonia?

Answer 66

The response of the lungs to aspirated foerign material will depend on the nature of the material - the bacterial load and the distribution of the material within the lungs. this type of pneumonia can develop into a severe necrotising pneumonia and in very severe causes can progress to gangrenous pneumonia.

Question 67

What is gangrenous pneumonia?

Answer 67

Can occur following severe infections in which tissue becomes necrotic and is then invaded by putrefactive saprophytes, however, this is rare. The usual cause is administration of medicines intended for the oesophagus or as a sequel to aspiration pneumonia. The dead tissue undergoes liquefactive necrosis forming a cavity which is surrounded by intense hyperaemia and inflammation.

Question 68

What is lipid pneumonia?

Answer 68

Endogenous: Accumulation of lipids in pulmonary macrophages - multifocal white nodules Exogenous: associated with inhalation of oil, paraffin etc This results in a reaction dominated by macrophages which fill the alveoli and interstitial thickening.

Question 69

What is uraemic pneumonia?

Answer 69

Severe uraemia causes increased permeability of the blood air barrier and therefore can cause pulmonary oedema. In addition to the oedema, there may also be degeneration and calcification of smooth muscle and connective tissue fibres.

Question 70

What is Atelectasis?

Answer 70

The incomplete expansion of the lung at birth (congenital) or collapse of previously air filled lung (acquired).

Question 71

What is obstructive atelectasis?

Answer 71

Caused by complete airway obstruction, usually by inflammatory exudate, foreign bodies, parasites or tumours In species with good collateral ventilation complete blockage of lobar or segmental bronchi is necessary for obstructive atelectasis.

Question 72

What is compression atelectasis?

Answer 72

Caused by pleural, intra thoracic or intrapulmonary space occupying lesions. Fluid, blood or exudate can cause compression atelectasis In large animals this commonly occurs below a sharply demarcated fluid line.

Question 73

What is emphysema?

Answer 73

An important primary disease in humans (protease/antiprotease imbalance causing alveolar wall destruction), in veterinary species it is secondary to some underlying entity. Increased air in the lungs does occur importantly as an Agonal change at slaughter and secondary to obstruction of airflow.

Question 74

Describe secondary pulmonary emphysema

Answer 74

Alveolar: distension and rupture of alveolar walls - formation of air bubbles in the parenchyma. Interstitial: most common in cattle due to pulmonary microanatomy. Air - Interlobular connective tissue and can form bullae bullous emphysema.

Question 75

Disturbances of the circulation make the lung vulnerable to what?

Answer 75

Pulmonary oedema - normally mechanisms are in place to protect the lung from the entry of circulatory fluid into alveolar spaces. These are: alveolar epithelium and its intercellular junctions are highly impermeable to fluid and seal off alveolar spaces, interstitium of alveolar septa is at lower pressure than intra alveolar pressure. Interstitial pressure becomes increasingly sub atmospheric toward the fascia surrounding vessels and airways and towards the pulmonary hilus.

Question 76

What is pulmonary oedema?

Answer 76

Excessive fluid in the lung which generally begins as interstitial oedema characterised by expansion of perivascular and peribronchial and peribronchiolar fascia and distension of interstitial lymphatics. When this interstitial compartment is overwhelmed, fluid floods the airspaces causing alveolar oedema.

Question 77

What are the major causes of Pulmonary oedema?

Answer 77

Increased capillary or type I epithelial permeability caused by - systemic toxins, shock, inhaled caustic gases. Increased capillary hydrostatic pressure. Decreased plasma oncotic pressure

Question 78

What is pulmonary haemorrhage?

Answer 78

A potential sequel of septicaemias, bleeding disorders, disseminated intravascular coagulation and severe congestion. Exercise - induced pulmonary haemorrhage occurs commonly in horses during racing or training. Haemorrhage is dorsocaudal.

Question 79

Describe embolism, thrombosis and infarction in the lungs

Answer 79

The lungs are situated where they catch emboli carried in venous blood. Because the lung is supplied by both pulmonary and bronchial arteries and has extensive collateral channels, infarction usually does not follow embolism or thrombosis unless pulmonary circulation ins already compromised. Pulmonary infarcts usually occur when there is embolisation or thrombosis during general circulatory collapse or passive congestion of heart failure.

Question 80

What causes pulmonary hypertension?

Answer 80

Caused by left to right vascular shunts or increased resistance of the pulmonary vascular system. In animals it is most commonly a sequel of widespread fibrosis in the lung or chronic bronchitis or bronchiolitis which stimulates hypertrophy in the walls of small arteries. Severe prolonged pulmonary hypertension leads to cor pulmonale. - right sided heart failure.

Question 81

Describe Neoplasia of the Lower airway

Answer 81

Although metastatic pulmonary tumours are common in the lung, pulmonary primary tumours are rare in domestic animals - more common in dogs and cats. Classification can be difficult due to the metaplasia which can occur in both inflammation and neoplasia - Bronchial papilloma, bronchial adenoma, bronchiioalveolar adenoma, carcinoid (rare in animals)

Question 82

What is sheep pulmonary adenomatosis? (SPA/jaagsiekte)

Answer 82

SPA is caused by a retrovirus and is common under intensive management systems which favour aerosol transmission of disease. The lesions progress from small firm grey/white nodular lesions to extensive confluent areas with replacement by neoplastic tissue. There is often coexistent infection present. Occasional metastases to bronchial and mediastinal lymph nodes.

Question 83

What are bronchioalveolar tumours?

Answer 83

Most common in dogs - may be an incidental necropsy finding. Often occur as solitary nodules at the periphery of the lung. Note however that rapid metastatic spread of tumour from a primary elsewhere in the body can mimic the pattern of a bronchioloalveolar tumour.

Question 84

Give some common examples of metastatic tumours of the lungs

Answer 84

Mammary carcinoma, uterine adenocarcinoma, malignant melanoma. Metastatic tumours often manifest as multiple nodules scattered throughout the parenchyma - these lesions are often referred to as cannon ball metastases.

Question 85

What is pneumothorax?

Answer 85

Presence of air in the pleural cavity. Atelectasis proportional to the amount of air in the cavities always accompanies pneumothorax. Pneumothorax can be spontaneous or traumatic. In animals it is usually caused by traumatic rupture of the lung or perforation of the thoracic wall.

Question 86

what are Hydrothorax, chylothorax and haemothorax?

Answer 86

Non inflammatory pleural effusions. Hydrothorax is the accumulation of oedema fluid and has the same causes as oedema elsewhere. Chylothorax is the accumulation of chylomicron rich lymph generally through traumatic or inflammatory rupture of the thoracic lymphatic duct. Haemothorax is the presence of blood in the pleural cavity.

Question 87

What is pleuritis?

Answer 87

Inflammation of the pleura. Inflammatory agents reach the pleura by; extension from pneumonia, bloodstream, trans-diaphragmatic lymphatics from peritoneal cavity, penetration of the chest, penetration from oesophagus or abdominal viscus. Purulent and fibrinous pleuritis are common acute forms.

Question 88

What is pyothorax? (thoracic empyema)

Answer 88

A purulent effusion in the pleural space. In horses it is usually secondary to pneumonia or lung abscesses. Streptococci most common.

Question 89

Describe neoplasia of the pleural cavity

Answer 89

Mesothelioma - most common in calves, often causes thoracic effusion, multiple nodular masses on pleural surface, diagnosis can be difficult due to cytological similarity of reactive and neoplastic mesothelial cells.