classification of pneumonias in dtiaildomestic...

Tutorial Module 4Tutorial Module 4

Classification of Pneumonias in Classification of Pneumonias in D ti A i lD ti A i lDomestic AnimalsDomestic Animals

Alfonso LópezAlfonso LópezAtlantic Veterinary CollegeAtlantic Veterinary Collegey gy g

University of Prince Edward IslandUniversity of Prince Edward Island

CanadaCanada

©2009©2009 EneroEnero 3131

One of the most controversial topic in One of the most controversial topic in pathology and veterinary medicine is pathology and veterinary medicine is pat o ogy a d ete a y ed c e spat o ogy a d ete a y ed c e s

the CLASSIFICATION OF PNEUMONIASthe CLASSIFICATION OF PNEUMONIAS

Just remember that there is no best or universal classification. Just remember that there is no best or universal classification.

These are some of the many criteria used in veterinary medicine These are some of the many criteria used in veterinary medicine PPNN

ese a e so e o t e a y c te a used ete a y ed c eese a e so e o t e a y c te a used ete a y ed c e

EPIDEMIOLOGIC CRITERIA: EPIDEMIOLOGIC CRITERIA: Enzootic, Enzootic, ContagiousContagious, Progressive , Progressive

EEUUMM

MORPHOLOGIC CRITERIA: MORPHOLOGIC CRITERIA: GangrenousGangrenous, , Lymphocytic, ProliferativeLymphocytic, Proliferative, , ExudativeExudative

ETIOLOGY CRITERIA : ETIOLOGY CRITERIA : Bacterial, Viral, Mycotic, Parasitic, Aspiration Bacterial, Viral, Mycotic, Parasitic, Aspiration MMOONN

MISCELLANEOUS CRITERIA: MISCELLANEOUS CRITERIA: AtypicalAtypical, , Cuffing, Neonatal, Calf, Shipping Fever Cuffing, Neonatal, Calf, Shipping Fever

CLINICAL CRITERIACLINICAL CRITERIA BRD C l tBRD C l t diff ti t ddiff ti t dIIAA

CLINICAL CRITERIA: CLINICAL CRITERIA: BRD Complex, acute BRD Complex, acute undifferentiated undifferentiated

DISEASE CRITERIA: DISEASE CRITERIA: Distemper pneumonia, tuberculosis, IBR, Distemper pneumonia, tuberculosis, IBR,

Based on TEXTURE, DISTRIBUTION and TYPE OF EXUDATE, Based on TEXTURE, DISTRIBUTION and TYPE OF EXUDATE, pneumonias in Domestic Animals can be grossly classified into pneumonias in Domestic Animals can be grossly classified into

GGRR p g yp g y

FIVE morphologically distinct typesFIVE morphologically distinct typesRROOSS

Suppurative BronchopneumoniaSuppurative Bronchopneumonia

Fibrinous BronchopneumoniaFibrinous Bronchopneumonia

SSSS

Fibrinous Bronchopneumonia Fibrinous Bronchopneumonia

Interstitial PneumoniaInterstitial PneumoniaFFEE

Embolic Pneumonia Embolic Pneumonia

G l t iG l t i

AATT

Granulomatous pneumoniaGranulomatous pneumoniaUURR

This gross classification allows you to predict the most likely port of entry, This gross classification allows you to predict the most likely port of entry, EESS

gives you a good idea for rulegives you a good idea for rule--outs which help you to decide which outs which help you to decide which laboratory tests you should requested. laboratory tests you should requested. Therefore, increases Therefore, increases your chances your chances to arrive to arrive at at the most likely etiological the most likely etiological diagnosis.diagnosis.


•• Distribution: Distribution: CranioventralCranioventralnormal

•• Texture: FirmTexture: Firm

•• Color: Red (acute) to grey (chronic)Color: Red (acute) to grey (chronic)

•• Cut surface: purulent exudate in bronchiCut surface: purulent exudate in bronchi

P tP t f tf t AA•• Port Port of entry: of entry: AerogenousAerogenous

•• Common Common etiologies:etiologies:

•• Bacteria (low grade Bacteria (low grade pathogenicitypathogenicity))•• MycoplasmaMycoplasma•• Aspiration of bland materialAspiration of bland material

Bovine lung

•• Most common sequels: Most common sequels: CranioventralCranioventral abscesses and abscesses and bronchiectasisbronchiectasis


NNNN

CCCC

Another example of a Suppurative Bronchopneumonia in a Pig

Note cranioventral consolidation (C) while the caudal lung remains unaffected (N). The texture of consolidated lung would be firmer than normal. Typically, on cut surface purulent exudate could be expressed from bronchi (arrow).

Suppurative Bronchopneumonia

Normal

Consolidated

S i B h i i PiSuppurative Bronchopneumonia in a Pig

Another example of a suppurative bronchopneumonia. Note once again that consolidation is restricted to the cranioventral lung while the caudal lung (CL) remains unaffected. There is also a l b l tt t i l f ti b h i ( di ) Th t t flobular pattern typical of suppurative bronchopneumonia (see diagram). The texture of consolidated lung would be firmer than normal and on a cut surface purulent exudate could be expressed from bronchi. The more chronic the lesion, the more mucus in the exudate expressed from bronchi.

Cut surface of Cut surface of lung lung showing purulent showing purulent exudate coming out of the bronchiexudate coming out of the bronchi Suppurative Bronchopneumonia

The The gross appearance gross appearance of the of the exudate in suppurative exudate in suppurative bronchopneumonia bronchopneumonia varies from varies from purulent in acute cases topurulent in acute cases topurulent in acute cases to purulent in acute cases to mucopurlentmucopurlent or or mucoidmucoid in more in more chronic cases. chronic cases.

The presence of mucus in theThe presence of mucus in theThe presence of mucus in the The presence of mucus in the exudate is due to severe goblet exudate is due to severe goblet (mucus) cell hyperplasia in (mucus) cell hyperplasia in bronchi and goblet cell bronchi and goblet cell

l i i b hi ll i i b hi lmetaplasia in bronchioles.metaplasia in bronchioles.

Note the light color of the normal lung and the Note the light color of the normal lung and the darker hyperemic color of the pneumonic lung.darker hyperemic color of the pneumonic lung.

Note also purulent exudate coming out of a major Note also purulent exudate coming out of a major b h hi h i t i l f tib h hi h i t i l f tibronchus which is typical of suppurative bronchus which is typical of suppurative bronchopneumonia. bronchopneumonia.

The color of The color of consolidated consolidated lung lung varies varies according to according to chronicitychronicity from:from:gg yy

•• Bright Bright red in acute red in acute supppurativesupppurativebronchopneumonia (severe bronchopneumonia (severe hyperaemiahyperaemia ++ small exudatesmall exudate))

AcuteAcute

hyperaemiahyperaemia + + small exudatesmall exudate) )

•• Dark red in Dark red in subacutesubacute suppurtivesuppurtivebronchopneumonia (less hyperemia bronchopneumonia (less hyperemia ( y( yand more purulent exudate)and more purulent exudate)

•• Pale grey Pale grey resembling fishresembling fish--flesh in flesh in chronicchronic suppurativesuppurative bronchobroncho

SubcuteSubcute

chronic chronic suppurative suppurative bronchobroncho--pneumonia pneumonia (exudate, fibrosis, (exudate, fibrosis, and and less blood because reduced volume less blood because reduced volume density of pulmonary density of pulmonary capillaries). capillaries).

ChronicChronic

The main microscopic lesion in suppurative The main microscopic lesion in suppurative bronchopneumonia would be neutrophils and bronchopneumonia would be neutrophils and macrophages in macrophages in bronchoalveolarbronchoalveolar spaces (see next slide).spaces (see next slide).

Suppurative Bronchopneumonia

Subacute, Suppurative bronchopneumonia / H&E stain/

Hi t l i l ti f l ithHistological section of a lung with suppurative bronchopneumonia. Note a bronchiole plugged with purulent exudate (pe). Also note large number of neutrophils

i d ith d t fl id i l limixed with edematous fluid in alveoli, hence the name bronchopneumonia.

The pathogenesis of this lesion is related to l f h t ti f t lrelease of chemotactic factors on mucosal

surface of bronchi, bronchioles and alveoli causing migration of neutrophils into the airways.

In uncomplicated cases, the exudate moves along the mucociliary escalator. In severe cases, the excessive release of l k ti d thleukocytic enzymes damages the mucosa, submucosa, smooth muscle and cartilage, causing bronchiectasis (see next slide).

Pulmonary Abscesses

Pulmonary abscesses and bronchiectasis are two important sequels to suppurative bronchopneumoniaPulmonary abscesses and bronchiectasis are two important sequels to suppurative bronchopneumonia.

Note large abscesses in the cranial and intermediate lobes. The caudal lobes are essentially normal. Histologically, abscesses are composed of a purulent core surrounded by connective tissue (pyogenic membrane).

Bronchiectasis

Bronchiectasis is the rupture and dilation of bronchi due to enzymatic and destructive effect of neutrophils and macrophages on the bronchial wall in chronic bronchopneumonia.

Note tubular dilations in the cranioventral lung (white arrows). These tubular structures are distended bronchi filled with purulent exudate that has destroyed thestructures are distended bronchi filled with purulent exudate that has destroyed the bronchial walls (insert). These lesions may look like abscesses. However, microscopically instead of being lined by a capsule it is lined by remnants of bronchial walls which contain purulent exudate (red arrows).

• Distribution: cranioventral

Fibrinous Bronchopneumonia

• Texture: Hard

• Color: Red yellow grey

normal

• Fibrin on pleural surface

• Cut surface: fibrin / necrosis

• Port of entry: aerogenous

• Most common etiologies:

• Highly pathogenic bacteria (exotoxins):

Mannhemia haemolytica, Actinobacillus

pleuropneumoniae;pleuropneumoniae;

• Harsh aspirated materials

• Implies severe injury to the lung

• Sequels: Sequestrum, pleural adhesions


Note cranioventral consolidation and affected lung covered with fibrin. Only a small portion of the lung appears grossly normal (asterisk)


****

Note cranioventral consolidation with affected lung covered with a thick layer of fibrin. Only the dorsocaudal lung appears normal (asterisk). Remember, the texture of consolidated lungs in fibrinous bronchopneumonia is typically hard.


Cut surface of lung

Fibrinous bronchopneumonia generally implies severe injury to the lung with p j y gleakage of fibrin into the airspaces.

On cut surface, fibrinous bronchopneumonia often has a mosaic appearance due to ppdistention of the interlobular septa in areas of coagulation necrosis.

Note in this photograph a mosaic gappearance of the lung. The arrows delineate distended interlobular septa that results from lymphatic thrombosis and edema.

Hi hl th i b t i th t

Note also areas of coagulation necrosis (asterisks).

• Highly pathogenic bacteria that produce exotoxins such as• Mannheimia haemolytica• Actinbacillus pleuropneumoniae

This particular case is Shippping Fever Pneumonia caused by the toxins of Mannheimia haemolytica A1


** **

Histopathology H&EHistopathology H&E.

Note loss of airspaces due predominantly to exudation of fibrin (asterisks) and to a lesser extent of leukocytes. In this type of pneumonia hemorrhages are also common.

Since fibrin predominates over polymorphonuclear leukocytes, the

**polymorphonuclear leukocytes, the diagnosis of fibrinous is preferred to that of suppurative bronchopneumonia.

Remember that fibrin is chemotactic for t hil d th f fib ineutrophils and therefore any fibrinous

pneumonia has neutrophils microscopically.

4 other examples of Fibrinous Bronchopneumonia

4 other examples of Fibrinous Bronchopneumonia

Pleural Adhesions are important sequel to bronchopneumonia.

fNote in all cases bands of connective tissue (arrows) between the lung and the parietal pleura lining the thoracic cavity. Adhesions are commonly seen in

li h h i l h dpostmortems revealing that the animal had or survived a previous episode of bronchopneumonia. Adhesions between pleura and pericardium are also common.

Pleural Adhesions / 3 cases

Lung sequestrum (plural sequestra) is also a

Lung Sequestrum11

sequel sometimes seen in fibrinous

bronchopenumonia. Simply put it, a sesquestrum

is a large piece of necrotic lung that becomes

isolated from the surrounding pulmonary tissue.

Figure 1. Severe fibrinous pneumonia in a cow

h i f l f t i ( llshowing focal areas of acute necrosis (small

circle). If the animal had survived, these areas of

necrosis could become isolated from the remaining

l f i t22 lung forming a sequestrum.

Figure 2. These lungs show a large wall-off

pulmonary sequestrum This was a case of

22

pulmonary sequestrum. This was a case of

Contagious Bovine Pleuropnemonia (Mycoplasma

pleuropneumoniae) that is enzootic in some

countries in Asia and Africa but non existent in thecountries in Asia and Africa, but non-existent in the

Americas. If you were to cut this sequestra it

would be composed of pure necrotic tissue.Plum Island

INTERSTITIAL PNEUMONIAINTERSTITIAL PNEUMONIA

• Distribution: Diffuse

• Texture: Elastic

• Cut surface: meatyCut surface: meaty

• Gross Features:

• Rib imprints

• Lungs failed to collapse when thorax is

opened

P t f t A H t• Port of entry: Aerogenous or Hematogenous

• Most common etiologies: Virus, toxins, type III hypersensitivity, toxicants

• Pathogenesis: Injury centered in the alveolar wall (endothelium or pneumocytes)

• Histology: Thickening of the alveolar walls

• Important Feature: Often difficult to diagnose grossly


VirusVirusToxinToxinToxinToxin

SepsisSepsisAllergicAllergic

Acute severe diffuse interstitial pneumonia / HorseAcute, severe, diffuse interstitial pneumonia / Horse.

Note discreet rib imprints on pleural surface which resulted from lack of deflation at the time when the negative pressure was removed by opening the thorax.

Acute, severe, diffuse interstitial pneumonia / Lamb.


This is another example of an interstitial pneumonia. Note again rib imprints on the pleural surfaces (arrows) of this lamb that died acutely with adenovirus pneumonia.y p

Remember that the pleural imprints result from lack of deflation at the time when the negative pressure is removed by opening the thorax.p y p g

Changes are often subtle , difficult to diagnose grossly and generally require histopathological confirmation.

On cut surface, the lung tissue in interstitial pneumonia has an elastic texture and a meaty appearance.pp

The primary lesion is centered in the alveolar wall. Thickening of alveolar walls results from interstitial infiltration of mononuclear cells or from proliferation of type II pneumocytes. In chronic interstitial pneumonia, there is alveolar fibrosis.

Steer.

Interstitial PneumoniaInterstitial Pneumonia

Steer.

This lung belonged to a steer that died a few days after severe respiratory distress. The lungs failed to collapse when the thorax waslungs failed to collapse when the thorax was opened and there were rib imprints on pleural surface. The texture of this lung was notably elastic.

Note some edematous distention of the interlobular septa (arrows) and "meaty” appearance of the parenchyma.

Interstitial pneumonia is perhaps the most difficult type of pneumonia to diagnose grossly. In most cases it is imperative to do histopathology The basic lesion in interstitialhistopathology. The basic lesion in interstitial pneumonia is the thickening of alveolar septa which is what gives it the elastic texture and prevents alveoli from collapsing.

Microscopic view of the basic interstitial pneumonia is illustrated in the next slide.

Interstitial PneumoniaInterstitial Pneumonia

Steer. Histopathology. HE stain

Note thick alveolar walls (arrows) due to increased cellularity of the alveolar walls and yinterstitium (asterisks).

Thickening of alveolar walls can result from influx of inflammatory cells or fluid into the yinterstitium or from proliferation of hyperplastic type II pneumonocytes.

In chronic cases, interstitial pneumonia may , p yprogress to interstitial fibrosis and the lesion is often called "fibrosing alveolitis.”

Interstitial pneumonia results from alveolar pdamage caused by viral infections, deposition of antigen-antibody complexes, inhalation of toxic gases (nitrogen dioxide, sulfur dioxide, ozone, oxygen toxicity), or ingestion of yg y) gtoxicants that damage bronchioles and alveoli such as the herbicide paraquat or some mycotoxins.

• Distribution: Multifocal

Embolic PneumoniaEmbolic Pneumonia


• Texture: Nodular

• Port of entry: Hematogenous

• Color: red when acute, pale when chronic

• Most common etiologies:

• Rupture of hepatic abscesses into the vena

cava in cattle

• Vegetative endocarditis (right side of the

heart)heart)

• Jugular thrombosis

• Embolic foreign body (hair, septic emboli,

etc).

Note multifocal hemorrhagic lesions randomly g ydistributed in all pulmonary lobes (arrows). Also note that the center of the hemorrhagic foci is often white, suggesting neutrophilic inflammation.

Dog with Dog with valvularvalvular endocarditisendocarditis


Note numerous foci of inflammation scattered throughout the lungs (arrows)

See Figure 9-41 Pathologic Basis of Veterinary Diseases


Foal.Sometimes the embolic lesions are very small and difficult to see as in the lungs of this foal. Look closely in the inset and you will notice small dark foci with white center (arrows).

Foal.Sometimes the embolic lesions are very small and difficult to see as in the lungs of this foal. Look closely in the inset and you will notice small dark foci with white center (arrows).


Histopathology

Note foci of neutropilic inflammation lungNote foci of neutropilic inflammation lung

Embolic PneumoniaEmbolic PneumoniaEndocarditis (arrow) is a common Endocarditis (arrow) is a common cause of embolic pneumoniacause of embolic pneumonia

Fig. 9-41. Lopez a, In: PBVDMcGavin MD Zachary JFMcGavin MD, Zachary JFMosby, 2007

Note numerous foci of inflammation in the lungs. The focal lesion have a white color because they are chronic and the initial hemorrhage has been resolved. These focal lesions are evolving towards small abscesses

Sequel to Embolic Pneumonia: Pulmonary abscessesSequel to Embolic Pneumonia: Pulmonary abscesses

Note numerous small abscesses resulting form septic embolisms due to vegetative endocarditis affecting the tricuspid valve (right side) of the heart. Septic emboli are easily trapped in pulmonary vasculature causing embolic pneumonia and it’s sequel pulmonary abscesses.p y g p q p yBronchopneumonia may also have abscesses as sequels, except that in this latter type of pneumonia the distribution is cranioventral and not random as in embolic pneumonia.


Granulomatous PneumoniaGranulomatous Pneumonia


• Texture: Nodular (no pus)

• Cut surface: granulomas• Cut surface: granulomas

• Port of entry:

Aerogeno s• Aerogenous

• Hematogenous

• Etiology:

Source unknown

• Etiology:

• Myocbacterium spp

• Systemic mycosesSystemic mycoses

• Parasitic ova

• Trapped food particles (starch)

• Dead parasites

Granulomatous Pneumonia in Bovine Tuberculosis

Granulomatous Pneumonia in Bovine Tuberculosis

•Note numerous focal to coalescing granulomas scattered throughout the lung parenchyma.

• Granulomatous pneumonia is typically caused by organisms or particles that cannot be readily d t d b h i th d i t t t h t i h M b t idestroyed by macrophages or in other words resistant to phagocytosis such as Myocabcteria, fungus, parastic ova, dead larvae, etc.

•The texture of this lung would be nodular.

Granulomatous Pneumonia

Chronic, severe, multifocal granulomatous pneumonia / Canine Blastomcycosis.

N i l h fill d i h di i d f fl l Th di ib iNote entire lung parenchyma filled with medium sized, often confluent granulomas. The distribution of granulomatous pneumonia is random and multifocal affecting all pulmonary lobes. The port of entry in granulomatous pneumonia could be either aerogenous or hematogenous. Texture is typically nodular.

Chronic, severe, multifocal granulomatous pneumonia.

Equine Tuberculosis / Lung - Cut surface. Granulomatous Pneumonia

Numerous focal to coalescing granulomas in lung parenchyma.

T b l i ff t ti i l diTuberculosis can affect any tissue including bones, bone marrow, gonads, kidneys, meninges, etc.

M b t i t b l i ll ff tMycobacterium tuberculosis generally affects humans, but cross infections with M. bovis and M. avium can also occur. Pigs can be affected by all three species. Remember that typical

l t l i i dgranulomatous lesions seen in cows and sheep (caseous necrosis and calcification) with tuberculosis are not seen in horses, cats and dogs. In these other animals tubercles have th f t l ththe appearance of tumoral growths (sarcomatous).

Sometimes tumor and granulomas are not il di ti i h bleasily distinguishable.

Acid fast stain reveals the TB bacillus.

Granulomatous Pneumonia

Note typical granuloma macrophages in the center and an external band of fibrous connective tissue (double arrows) infiltrated by lymphocytes and plasma cells y y p y p(not seen at this magnification).

In most granulomatous pneumonias, the etiologic agent can be detected with special g g pstains (to be shown later). Among the most common causes of granulomatous pneumonia in animals are:

• Tuberculosis

• Systemic mycosis (Cryptococcus neoformans, Blastomyces dermatitides, yCoccidiodes immits)

• Aberrant parasitic larvae, foreign body (food particles), algae.p ) g

• Feline Infectious Peritonitis in cats, etc.Granulomatous pneumonia. Histopathology

TheThe 55 gross morphologic types ofgross morphologic types of

SUMMARY Suppurative BronchopneumoniaSuppurative Bronchopneumonia

The The 5 5 gross morphologic types of gross morphologic types of Pneumonia in Domestic Animals Pneumonia in Domestic Animals

Fibrinous BronchopneumoniaFibrinous Bronchopneumonia


Interstitial PneumoniaInterstitial Pneumonia Granulomatous PneumoniaGranulomatous PneumoniaInterstitial PneumoniaInterstitial Pneumonia

Some images were acquired from veterinary colleges of Some images were acquired from veterinary colleges of Canada, United States and Mexico and the names ofCanada, United States and Mexico and the names ofCanada, United States and Mexico and the names of Canada, United States and Mexico and the names of pathologists who contributed with some slides are known. pathologists who contributed with some slides are known. Their valuable contribution is sincerely acknowledged.Their valuable contribution is sincerely acknowledged.

I would like to thank Adriana Lopez, University of Western I would like to thank Adriana Lopez, University of Western Ontario, and Eileen Ontario, and Eileen KinchKinch for editorial assistance; Dr. for editorial assistance; Dr. María Forzán, Atlantic Veterinary College, for critically María Forzán, Atlantic Veterinary College, for critically reviewing these modules.reviewing these modules.

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If you have any comments, criticisms or suggestions about these If you have any comments, criticisms or suggestions about these

tutorial modules please let me know. tutorial modules please let me know.

Also, if you find any errors or typos please let me know too Also, if you find any errors or typos please let me know too

lopez@upeicalopez@upeica

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