I. Gross examination of the thoracic cavity
A. Puncture diaphragm from abdominal cavity to as- sess negative pressure in thorax
1. Perceivable inrush of air to thorax and billow- ing of diaphragm toward abdomen if animal has been dead less than a few hours
2. Lack of this movement may indicate pneumo- thorax, pleural effusion, or noncollapsible lungs owing to pulmonary edema, pneumonia, fi brosis, or emphysema
B. Rib cage
1. Fibrinous adhesions between visceral and pari- etal pleura indicate acute pleuritis
2. Fibrous adhesions between visceral and pari- etal pleura indicate chronic pleuritis or healed lesions from previous pleuritis
3. Check for rib fractures
C. Tongue, pharynx, larynx, trachea, bronchi, lungs, and heart are removed as one (“pluck”), and ex- amined outside of the animal
D. Estimate volume of fl uid, if any, in thoracic cavity. A small volume of serous fl uid is normal
II. Nasal cavities
A. Turbinate atrophy (e.g., atrophic rhinitis of swine [Pasteurella multocida type D])
B. Catarrhal rhinitis
1. Increased volume of mucous exudates 2. Bacterial or viral causes or implies relatively
mild infl ammation
C. Suppurative rhinitis: Bacterial causes are most likely
D. Granulomatous rhinitis
1. Thick, less fl uid exudate or no grossly visible exudates
2. Chronic
3. May be thickening of mucosal lining or polyp- oid nodules
4. Fungi, higher bacteria, foreign bodies III. Sinuses
A. Sinusitis often occurs in combination with rhinitis. May be a sequela to septic wound (e.g., dehorning in cattle, tooth infection in horses and dogs) B. Chronic sinusitis may extend into adjacent bone
(osteomyelitis) or cribriform plate to cranial cavity (leading to meningitis or encephalitis) C. Common causes of rhinitis and sinusitis
1. Horses
a. Equine herpesvirus (EHV-1 and EHV-4) b. Equine infl uenza virus
c. Equine adenovirus (especially severe in Arabian foals with combined immunodefi ciency)
2. Cattle
a. Infectious bovine rhinotracheitis virus (BHV-1). Pseudomembranous or fi brinonecrotic
b. Malignant catarrhal fever (bovine herpesvirus-2 outside of Africa). Ocular and nervous system infl ammation as well
3. Swine
a. Atrophic rhinitis (Pasturella multocida type D) b. Inclusion body rhinitis (cytomegalovirus, a
herpesvirus) 4. Dogs
a. Canine distemper virus, canine adenovirus types 1 and 2, parainfl uenzavirus
b. Bordetella bronchiseptica, P. multocida,
Escherichia coli
c. Aspergillus spp., Cryptococcus neoformans,
Rhinosporidium seeberi
5. Cats
a. Feline viral rhinotracheitis (FVR; herpesvirus-1), feline calicivirus b. Chlamydia felis. Also conjunctivitis c. Mycoplasma felis. Also conjunctivitis d. Cryptococcus neoformans
IV. Pharynx, larynx, and trachea A. Anomalies
1. Brachycephalic airway syndrome (dogs) a. Stenotic nares, elongated soft palate b. Secondary nasal and laryngeal edema 2. Dorsal displacement of soft palate in horses.
Hypoplastic epiglottis prone to entrapment 3. Tracheal or tracheobronchial collapse
a. Toy and miniature breed dogs
b. Dorsoventral fl attening of trachea, with wide dorsal membrane
B. Laryngeal hemiplegia of horses
1. Idiopathic, traumatic, or infl ammatory injury to left recurrent laryngeal nerve
2. Muscle atrophy of dorsal and lateral cricoary- tenoideus muscles
C. Infl ammation 1. Redness
2. Fibrinous or suppurative exudate
3. May obstruct airfl ow or lead to secondary bronchopneumonia
4. Guttural pouch infl ammation in horses (Figure 7-1)
a. Aspergillus spp. b. Usually unilateral
c. Erosion into internal carotid artery may lead to epistaxis
d. Empyema of guttural pouches may be a se- quela to suppurative rhinitis, most com- monly caused by Streptococcus equi 5. Necrotic laryngitis (“calf diphtheria”)
a. Pseudomembranous
b. Fusobacterium necrophorum infection 6. Canine infectious tracheobronchitis (“kennel
cough”). Bordetella bronchiseptica, canine ade- novirus 2 or canine parainfl uenzavirus D. White, foamy fl uid in upper respiratory tract sug-
gests pulmonary edema
E. Free fi brin or suppurative exudate in the absence of redness or a pseudomembrane suggests infl am- mation from lower respiratory tract
V. Tracheobronchial lymph nodes
A. Red and wet suggest acute infl ammation
B. White or tan foci suggest necrosis, infl ammation, or lymphoid hyperplasia
VI. Lungs
A. Texture or consistency is the most important feature to evaluate
1. Spongy: Normal. Implies lung is adequately aerated
2. Rubbery
a. Atelectasis (i.e., not adequately infl ated, aerated, or expanded). Determine whether a newborn animal found dead took a breath by immersing a piece of lung tissue in water or fi xative
(1) If it fl oats, the animal took a breath (2) If it sinks, the animal was stillborn b. Fetal lungs should be atelectatic
c. Congested lungs may be slightly rubbery. Diffusely red, ooze blood on cut section d. Edematous lungs may be rubbery. Ooze wa-
tery or foamy fl uid on cut section 3. Firm or consolidated
a. Implies compromise of alveolar spaces (1) Exudate within alveolar spaces or
(2) Narrowing of alveolar spaces because of thickening of alveolar walls (often by in- fl ammation)
Figure 7-1 Guttural pouch empyema, guttural pouch, horse. A, Note
the swollen right neck (outlined) in this horse with guttural pouch empyema.
B, The guttural pouch is fi lled with masses of inspissated purulent exudate
(arrow). (A, Courtesy College of Veterinary Medicine, University of Illinois. B, Courtesy Dr. M.D. McGavin, College of Veterinary Medicine, University
of Tennessee.)
A
68 SECTION I GENERAL DISCIPLINES IN VETERINARY MEDICINE
b. Consolidation with retention of the shape of the lungs suggests infl ammation (i.e., pneumonia)
4. Patterns of pneumonia a. Diffuse
(1) Implies infectious agent entered lungs via bloodstream
(2) Typical pattern for viral pneumonias (3) Infl ammation is typically in the alveolar
walls, which means it is an interstitial
pneumonia
b. Locally extensive
(1) Cranioventral distribution implies infec- tious agent entered lungs via inhalation (2) Typical pattern for bacterial
pneumonias
(3) Infl ammatory exudate is typically in bronchi, bronchioles, and alveoli, which means it is a bronchopneumonia
(4) Aspiration pneumonia is a bronchopneu- monia. Exudate tends to be more necro- tizing than suppurative
c. Focal
(1) Abscess or granuloma (2) Blood-borne or inhaled agent d. Multifocal: Most likely, blood-borne infec-
tion (i.e., embolic pneumonia) B. Color
1. Red
a. Diffuse congestion (active or passive hyperemia)
b. Acute infl ammation
2. Gray-red, plum-colored, dark red, or purple a. Subacute to chronic infl ammation b. Atelectasis
3. White or tan areas or foci
a. Infl ammation (abscesses, granulomas) b. Fibrosis
c. Necrosis
C. Common causes of pneumonia 1. Horses
a. Rhodococcus equi: Bronchopneumonia in foals
b. Streptococcus equi: Bronchopneumonia c. Streptococcus zooepidemicus: Bronchopneu-
monia or pleuritis
d. Adenovirus (Arabian foals with combined immunodefi ciency disease [CID]). Broncho- pneumonia
e. Pneumocystis carinii (Arabian foals with CID). Interstitial pneumonia
2. Cattle
a. Mannheimia haemolytica: Acute broncho- pneumonia and pleuritis
b. Pasteurella multocida: Secondary opportunist; bronchopneumonia c. Mycoplasma bovis: Subacute to chronic
bronchopneumonia
d. Histophilus somni: Bronchopneumonia with or without pleuritis
e. Arcanobacterium pyogenes: Secondary opportunist; abscesses
f. Bovine respiratory syncytial virus
g. Infection with IBR virus, parainfl uenzavirus, or bovine viral diarrhea (BVD) virus may predispose to secondary bacterial pneumonia
3. Sheep and goats
a. Mannheimia haemolytica
b. Lentivirus (lymphoid interstitial pneumonia of sheep; caprine arthritis-encephalitis virus of goats)
c. Lungworms (Dictyocaulus fi laria, Muellerius
capillaris, Protostrongylus rufescens) 4. Swine
a. Pasteurella multocida: Bronchopneumonia b. Actinobacillus pleuropneumoniae
(1) Acute fi brinohemorrhagic bronchopneu- monia and pleuritis
(2) Preferentially affects dorsocaudal areas of the lungs
c. Mycoplasma hyopneumoniae: Subacute to chronic bronchopneumonia
d. Streptococcus suis type II: Bronchopneumo- nia or pleuritis
e. Myoplasma hyorhinis: Pleuritis as part of polyserositis syndrome
f. Hemophilus parasuis: Bronchopneumonia or pleuritis or polyserositis (Glasser disease)
g. Porcine respiratory and reproductive syn- drome (PRRS) virus
h. Porcine circovirus (postweaning multisys- temic wasting syndrome)
i. Swine infl uenzavirus 5. Dogs
a. Canine distemper virus b. Canine adenovirus type 2 c. Canine herpesvirus (neonates)
d. Bacterial pneumonias generally secondary to immunocompromise. Bordetella
bronchiseptica, Pasteurella multocida, E. coli, Klebsiella pneumoniae
e. Fungal pneumonias
(1) Blastomyces dermatitidis, Histoplasma
capsulatum, Coccidioides immitis, Crypto- coccus neoformans
(2) Aspergillus fumigatus (immunocompro- mised animals)
f. Toxoplasma gondii 6. Cats
a. Feline rhinotracheitis virus and calicivirus may cause pneumonia but not a signifi cant problem unless there is secondary bacterial infection
b. Cryptococcus neoformans VII. Neoplasms of the respiratory tract
A. Primary neoplasms are uncommon
1. Bronchogenic (bronchial origin), bronchiolar, alveolar, and bronchial gland carcinoma 2. Nasal adenocarcinoma
B. Lungs are a common site of metastasis of carcino- mas and sarcomas
VIII. Pleural effusions A. Hydrothorax
2. Common causes include right-sided heart fail- ure and hypoproteinemia
B. Hemothorax: Usually traumatic in origin C. Chylothorax: Most commonly due to ruptured
lymphatic duct (e.g., thoracic duct) D. Pyothorax: Common causes:
1. Ruptured lung abscess
2. Extension of pneumonia or pleuritis caused by pyogenic bacterium
3. Puncture wound of thoracic wall
4. Traumatic reticulopericarditis sequelae in cattle