Respiratory Disorders PDF

Respiratory Disorders 25 CH A P TE R Michal Mazaki-Tovi...

Respiratory Disorders 25 CH A P TE R Michal Mazaki-Tovi B. Laryngeal diseases DIAGNOSTIC METHODS FOR 1. History usually includes slowly progressive RESPIRATORY DISEASES signs, such as change of voice and inspiratory I. Upper respiratory tract stridor. Cyanosis and syncope may occur with A. Nasal cavity diseases laryngeal obstruction 1. History 2. Physical examination a. Sneezing and nasal discharge are the com- a. Auscultation can detect upper respiratory mon clinical signs. Gagging, reversed sneez- inspiratory stridor ing, or stertor may occur when the disease b. Palpation of the laryngeal area may detect extends to the nasopharynx pain, or asymmetry b. History should include the duration of clini- 3. Laryngoscopy and bronchoscopy cal signs, the type and site of involvement a. Evaluate pharyngeal structures, soft palate, of nasal discharge (unilateral or bilateral) and laryngeal movement with the patient 2. Physical examination under light anesthesia a. Sedation or anesthesia is usually required b. Endoscopic biopsy, aspiration, or brush b. Evaluate for asymmetry of the face, palate, cytology may be performed or eyes, areas of pain, patency of the nasal 4. Diagnostic imaging passages, and damaged teeth a. Laryngeal radiography may reveal 3. Laboratory testing elongated soft palate, fractures, or a. Complete blood cell count (CBC), serum emphysema biochemical profile, and coagulation tests b. Ultrasonography may demonstrate are warranted when a systemic disease is laryngeal paralysis suspected 5. Electromyography b. Serologic tests may be used in the diagnosis a. Neuromuscular, immune-mediated, and of mycotic rhinitis, but false-negative results hypothyroidism-related laryngeal disorders are common may be associated with abnormal studies of 4. Imaging the laryngeal muscles a. Skull radiography requires general anesthe- b. Histopathology may be helpful in the diag- sia. Radiographic views include open-mouth nosis of masses or polyneuropathy ventrodorsal, occlusal, rostral-caudal frontal C. Tracheal diseases skyline, lateral, and oblique 1. History b. Skull and nasal computed tomography (CT) a. Chronic, nonproductive, “honking” cough is may be used to delineate the extent of a a typical sign mass, bone lysis, and accumulation of fluids b. Inspiratory dyspnea may be present with c. Magnetic resonance imaging (MRI) may be cervical tracheal collapse and expiratory used for better definition of brain involvement dyspnea with intrathoracic collapse 5. Nasal flushing for cytology and biopsy 2. Physical examination a. Aggressive nasal flushing is required to a. Tracheal palpation may produce cough and yield sufficient tissue material detect sharp tracheal edges b. Submit samples for cytology and b. Perform cardiac examination and aus- histopathology cultate the entire respiratory tract to 6. Rhinoscopy differentiate the cough from other causes a. Requires general anesthesia such as cardiac or lower respiratory b. Allows visualization of mucosal lesions, disorders masses, or foreign bodies 3. Radiography c. Samples for histopathology, cytology, a. Both inspiratory and expiratory radio- culture, and sensitivity can be obtained graphs may be required to demonstrate with direct visualization collapsing trachea 7. Surgical biopsy may be obtained by b. Fluoroscopy allows dynamic evaluation of exploratory rhinotomy the trachea 353 354 SECTION II SMALL ANIMAL 4. Transtracheal wash (see below) 2. Transtracheal wash is performed in larger 5. Tracheoscopy may be helpful to visualize tra- dogs. A through-the-needle catheter is inserted cheal collapse, parasitic granulomas, foreign percutaneously under local anesthesia be- bodies, or neoplasia tween the tracheal rings or through the crico- II. Bronchopulmonary and pleural diseases thyroid membrane and then advanced into the A. History lower airway 1. Typical signs include coughing, tachypnea, 3. Endotracheal wash is performed in cats and dyspnea, and exercise intolerance small dogs. A catheter is inserted through a 2. Determine the duration of signs, the quality of sterile endotracheal tube and then advanced the cough (productive or nonproductive), the into the lower airway time of day of the cough (cardiac cough is 4. Bronchoalveolar lavage (BAL) may be usually nocturnal), travel history (infectious performed during bronchoscopy and allows diseases), and the presence of other signs retrieving airway fluid sample from the lower (systemic disease) airways B. Physical examination H. Lung biopsy 1. Observe the pattern of breathing: Slow, deep 1. Indicated when the cause of a diffuse lung breathing with inspiratory difficulty may disease cannot be determined by less invasive indicate obstructive upper airway disease; methods short, shallow breathing may be associated 2. May be obtained by fine-needle aspiration, with restrictive disease during bronchoscopy, using ultrasound or 2. Thoracic auscultation may reveal adventitious CT guidance, during thoracotomy (keyhole sounds, such as crackles (small airway or biopsy), or during thoracosopy parenchymal disease), rhonchi (airway I. Thoracocentesis is performed to obtain fluid for disease or exudate), and wheezes (airway analysis for diagnosis of pleural effusion obstruction) 3. Thoracic percussion may yield dull resonance NASAL CAVITY AND SINUSES (fluid or mass lesions within the pleural space or lung) or increased resonance (air) I. Congenital diseases C. Thoracic imaging A. Primary ciliary dyskinesia 1. Determine the type of pattern present 1. Uncoordinated and ineffective ciliary function (interstitial, alveolar, bronchial, or vascular) resulting in rhinitis, bronchitis, bronchiectasis, and distribution of the lesions (localized or and bronchopneumonia diffuse; cranial or caudal; and ventral, dorsal, 2. When associated with situs inversus, the or hilar) clinical syndrome is known as Kartagener 2. Thoracic ultrasound may be helpful for syndrome detection of small amounts of fluid, con- 3. Clinical signs include nasal discharge and solidated areas of lung and mediastinal coughing that begin at an early age masses 4. Diagnosis 3. CT may detect smaller pulmonary and pleural a. Measuring the velocity of mucus clearance lesions by using a drop of labeled macroaggregated D. CBC and serum chemistry albumin 1. CBC findings may include leukocytosis b. Analysis of cilia by electron microscopy (inflammation, infection), eosinophilia 5. Treatment is based on antibiotic therapy to (parasitic or allergic disease), polycythemia treat secondary infections (chronic hypoxemia), or nucleated red blood 6. Prognosis is guarded cells (acute hypoxemia) B. Cleft palate (see Chapter 27) 2. Serum biochemistry findings may indicate the II. Rhinitis and sinusitis of infectious origin presence of systemic disease A. Causes E. Arterial blood gas (ABG) 1. Dogs: Parainfluenza, distemper, adenovirus-2, 1. An arterial blood sample is usually drawn from Bordetella bronchiseptica, Aspergillus flavum, dorsal pedal artery or femoral artery Penicillium spp., Rhinosporidium seeberi 2. ABG analysis evaluates the animal’s ability to 2. Cats: Herpesvirus, calicivirus, Chlamydia psit- oxygenate arterial blood. In the normal patient taci, Bordetella bronchiseptica, Cryptococcus breathing room air, the partial pressure of neoformans oxygen should be 95 mm Hg. Elevations in 3. Chronic rhinitis is often associated with CO2 indicate ventilatory failure another predisposing problem such as F. Bronchoscopy allows direct visualization of the immunosuppression, foreign body, or tumor lower airway B. History G. Airway wash 1. Acute viral rhinitis is usually self-limiting 1. Warm sterile saline is instilled in the lower unless immunosuppression is present respiratory tract and then retrieved. Samples 2. Primary bacterial rhinitis occurs with Borde- are submitted for cytology and culture and tella bronchiseptica infection. Other bacterial sensitivity analyses nasal infections are usually secondary  CHAPTER 25 Respiratory Disorders 355 3. Aspergillus flavus is a normal inhabitant of III. Nasal parasites the nasal cavity, but it may invade respiratory A. Cuterebra, Eucoleus boehmi (nasal nematode), epithelium in dogs with altered immunity or Pneumonyssus caninum (nasal mite) mucosal injury B. Clinical signs include sneezing, nasal discharge, C. Clinical signs and reversed sneezing 1. Typical signs include sneezing and nasal C. Diagnosis is typically accomplished by direct discharge. Gagging or retching may occur due visualization. E. boehmi is diagnosed by mucosal to postnasal drip biopsy or identification of the ova on a fecal 2. Reversed sneezing may occur with nasopha- examination ryngeal involvement D. Treatment is by manual removal of large parasites D. Diagnosis or by treatment with oral ivermectin. 1. Dogs IV. Allergic rhinitis a. Serologic tests for aspergillosis and poly- A. Presumed to occur in dogs and cats merase chain reaction (PCR) for Bartonella B. Immunoglobulin E based rhinitis has not been b. Imaging includes open-mouth radiographs demonstrated yet or CT of the nasal cavity V. Nasopharyngeal polyps c. Rhinoscopy may reveal a foreign body, A. Inflammatory masses that arise from the epithe- a mass lesion, turbinate destruction, lium of the nasopharynx. Commonly occur in cats secretions B. Voice change is a common early sign. Gagging d. Histologic examination of nasal tissue is may also occur required for detection of hyphae of C. Otoscopic examination may reveal discharge and Aspergillus. Culture may be positive in polypoid masses within the external ear canal. normal dogs Oropharyngeal examination may demonstrate the e. Bacterial culture of mucosal biopsies may polyp by retraction of the soft palate be more indicative of infection. Culture D. Skull radiographs or CT may reveal increased of nasal secretions may be positive in density of one of the bullae or cranial to the normal dogs pharynx 2. Cats E. Treatment a. Serologic tests for feline immunodefi- 1. Removal of the mass by traction ciency virus, feline leukemia virus, and 2. Ventral bulla osteotomy is indicated for Cryptococcus removal of the inflammatory tissue when the b. Cytology from a nasal swab for detection of middle ear is involved Cryptococcus VI. Foreign body c. Tests for herpesvirus diagnosis A. Common in young dogs; grass awns and other (immunofluorescence, PCR). plant material especially common d. If empiric treatment fails, perform imaging, B. Signs include sneezing and nasal discharge rhinoscopy, and biopsy C. Plants material is usually not visualized on E. Treatment radiographs 1. Viral D. Rhinoscopy allows visualization and removal of a. Supportive care and broad-spectrum antibi- the foreign body in most cases otic treatment VII. Neoplasms of the nasal cavity and paranasal sinuses b. Lysine may be tried if herpesvirus infection A. In dogs, carcinomas are most common, followed is suspected by sarcomas. Transmissible venereal tumors are 2. Bacterial uncommon but should be considered in endemic a. Doxycycline is effective against B. bronchi- areas. Plasma cell tumors, mast cell tumors, and septica or Bartonella infections, and benign tumors occur rarely clindamycin has some efficacy against B. In cats, nasal and paranasal lymphomas are Mycoplasma most common, followed by adenocarcinoma and b. Treat underlying disorder (e.g., foreign squamous cell carcinoma. Benign nasopharyngeal body, tooth root abscess) inflammatory polyps are common 3. Fungal C. Malignant nasal tumors usually are locally a. Aspergillus flavus and Penicillium spp. are invasive, with metastasis occurring late in the most commonly treated with nasal tubes course of the disease for intranasal administration of clotrimazole D. Clinical signs or eniconazole. Oral therapy with ketocon- 1. Nasal tumors are more common in older azole, itraconazole, or thiabendazole is animals. Dolichocephalic and large-breed dogs generally less effective are predisposed. There is no sex predilection b. Rhinosporidium granulomas can be treated 2. Common clinical signs include sneezing, nasal by surgical extraction discharge, and epistaxis. Facial deformity c. Cryptococcus neoformans infection is occurs most commonly with skeletal treated with fluconazole, itraconazole, neoplasms. Seizures, blindness, and behavioral ketoconazole, or amphotericin B (alone changes may result from invasion to the or in combination with flucytosine) central nervous system 356 SECTION II SMALL ANIMAL E. Diagnosis E. Oropharyngeal examination under light anesthesia 1. Radiography of the nasal cavity and paranasal confirms the diagnosis. The arytenoids cartilages sinuses may demonstrate loss of trabecular are unable to abduct during inspiration. Laryngeal pattern, increase in soft tissue density, and edema may be present septal destruction. Thoracic radiographs may F. Treatment is by arytenoid lateralization indicate the presence of distant metastasis IV. Laryngeal neoplasms 2. CT and MRI are useful for evaluating the extent A. Generally rare in dogs and cats. Malignant tumors of the tumor are more common 3. Biopsy for histopathologic examination is re- B. Laryngeal tumors may be primary (e.g., squamous quired for diagnosis and may be acquired by a cell carcinoma, lymphoma, chondrosarcoma) or blind procedure, rhinoscopy, or rhinotomy metastatic (e.g., thyroid carcinoma) F. Treatment C. The most common clinical sign is inspiratory 1. Radiation therapy has been shown to increase dyspnea survival time in dogs and cats D. Diagnosis 2. Surgical cytoreduction in combination with radia- 1. Radiography may demonstrate laryngeal tion is rarely indicated for malignant tumors. Sur- distortion gery is the treatment of choice for nasal polyps 2. Laryngoscopic evaluation may reveal a mass 3. Chemotherapy is indicated for the treatment of 3. Diagnosis in confirmed by biopsy and lymphoma and transmissible venereal tumor histopathology E. Treatment 1. Surgical excision may be curative for benign UPPER AIRWAY DISORDERS tumors I. Brachycephalic syndrome 2. Radiotherapy and chemotherapy may be A. Consists of congenital disorders including beneficial for some tumors stenotic nares, elongated soft palate, and tracheal V. Tracheal stenosis hypoplasia (English bulldogs) and consequently, A. Usually results from traumatic tracheal injury laryngeal saccules eversion (e.g., bite wounds, intubation) B. Signs include characteristic stretor and snoring B. Signs include dyspnea and less commonly cough and occasionally exercise intolerance C. Thoracic radiographs demonstrate focal reduc- C. On physical examination stenotic nares may be tion of the tracheal lumen diameter evident D. Tracheoscopy is useful for assessing the location D. Oropharyngeal examination may reveal soft and severity of the stenosis palate overlapping on the epiglottis. Everted la- E. Treatment is by removal of the stenotic segment ryngeal saccules may be seen as oval mucosal by tracheal resection and anastamosis masses lateral to vocal folds VI. Tracheal collapse E. Treatment A. Causes 1. Nasal wedge resection 1. In dogs, abnormalities in chondrogenesis 2. Staphylectomy (congenital, inherited, or related to dietary 3. Laryngeal sacculectomy deficiencies) result in decreased turgidity of II. Laryngeal collapse the tracheal ring. Collapse may be found at A. Most commonly results from brachycephalic rest or may be dynamic, with cervical collapse syndrome found on inspiration and intrathoracic collapse B. Signs include stretor or stridor, dyspnea, and oc- on expiration. Collapse of smaller airways may casionally exercise intolerance be also present C. Oropharyngeal examination reveals apposition or 2. In cats, obstructive upper airway masses may overlap of the arytenoids cartilages cause tracheal collapse D. Treatment B. Pathophysiology 1. Treat predisposing factors (brachycephalic 1. The trachea usually collapses in a dorsoventral syndrome) orientation, causing trauma to the epithelial 2. If signs persist permanent tracheostomy may surface, mucus production, and perpetuation of be necessary cough III. Laryngeal paralysis 2. Reduction in airway radius increases resis- A. Diagnosed primarily in old, large-breed dogs tance to airflow and additional airway injury B. Interrupted innervation of the larynx results in C. Clinical Signs failure of the arytenoids cartilages to abduct 1. Small-breed dogs are typically affected with during inspiration tracheal collapse C. Congenital in some breeds (e.g., the Bouvier des 2. History Flandres). Might be associated with hypothyroid- a. Long-term history of chronic, intermittent ism or polyneuropathies. Many cases are idiopathic honking cough D. Clinical signs include stridor, voice change, and b. May be associated with gagging, retching, intermittent dyspnea, exacerbated by exercise, or syncope stress, or high environmental temperature. c. May exacerbate due to stress, heat, humid- Hyperthermia may occur ity, weight gain, and endotracheal intubation  CHAPTER 25 Respiratory Disorders 357 3. Physical examination B. Signs may include dyspnea and cough a. Gentle tracheal palpation may induce C. Thoracic radiography or CT may demonstrate cough. Sharp edges of the trachea may be foreign bodies or soft tissue density within the palpated at the collapsed area tracheal lumen or extraluminal masses b. High-pitched inspiratory sounds are heard D. Treatment over a narrowed cervical trachea 1. Foreign body can often be removed with an c. An end-expiratory snap may be heard over endoscope the thorax with intrathoracic collapse 2. Tracheal resection and anastamosis is required D. Diagnosis for tracheal neoplasia removal 1. Radiography a. Inspiratory and expiratory views are BRONCHOPULMONARY DISEASES recommended to evaluate for cervical or intrathoracic collapse. False-negative and I. Infectious tracheobronchitis (ITB) (see Chapter 18, false-positive are common Infectious Diseases) b. Fluoroscopy with induction of cough may II. Canine chronic bronchitis be useful A. Causes and pathophysiology 2. Bronchoscopy can confirm the presence of 1. Cause is unknown. Immunologic stimulation, collapse, identify passive or dynamic collapse, chronic mucosal irritation from air pollution, and determine the extent and grade of the or chronic aspiration of gastrointestinal (GI) disease content may cause chronic inflammation 3. Airway sampling should be obtained by 2. Neutrophilic infiltration of the airway induces tracheal wash or tracheobronchoscopy for epithelial injury, mucus accumulation, and cytology and culture (including Mycoplasma airway obstruction spp.) to identify conditions that may worsen B. History and clinical signs the signs 1. Middle-aged to older dogs, often overweight. E. Treatment Small- and large-breeds are affected 1. General: Weight reduction is beneficial in 2. Presence of chronic cough, which may be most cases. Limit exposure to environmental described as dry hacking or moist stressors. A harness should be used in place 3. The dog is typically not systemically ill of a collar 4. On physical examination, slow, deep respira- 2. Antitussives: Opiates (e.g., hydrocodone, tory pattern is typical. Prolonged expiration butorphanol) are most effective with an expiratory push may be apparent in 3. Bronchodilators: May be beneficial when severe cases. Expiratory wheezes and coarse there is evidence of concurrent small airway crackles may be evident on auscultation. disease Respiratory sinus arrhythmia is usually 4. Antiinflammatory drugs: A short course of present in dogs with chronic bronchitis prednisone may be required when tracheal and may be helpful to rule out congestive inflammation is present heart failure (CHF) as the primary cause for 5. Antibiotics: Bacterial infection is uncommon. the cough When suspected, doxycycline and enrofloxacin C. Diagnosis are good first choices pending culture results 1. The diagnosis is based on the history, clinical 6. Surgical stabilization has been successful in findings, thoracic radiographs, and airway reducing clinical signs in dogs with severe sampling to rule out other pulmonary causes tracheal collapse that failed to respond to of cough medical management. Serious complications 2. Generalized peribronchial infiltrates, character- occur occasionally ized by “doughnuts” or “tram lines,” are typical F. Prognosis: Irreversible disease. The goals of findings. Normal thoracic radiographs are com- treatment are to minimize clinical signs mon and do not rule out bronchitis (Figure 25-1) VII. Other causes of tracheal obstruction 3. Bronchoscopy is useful in the diagnosis and A. Causes typically shows airway hyperemia and a 1. Intraluminal foreign bodies rarely cause roughened appearance to the mucosa. In- complete obstruction creased mucus in the airways is present in 2. Extraluminal compression of the trachea may most cases. In some long-standing cases, be caused by compression from extraluminal nodular proliferations of the mucosa are masses such as thyroid carcinoma, hilar apparent lymphadenopathy, mediastinal masses, or 4. Airway sampling should be obtained through atrial enlargement endotracheal or transtracheal wash or with 3. Primary tracheal neoplasia is uncommon in bronchoscopy for cytology evaluation and dogs and cats culture a. Dogs: Osteosarcoma, chondrosarcoma, leio- 5. Typical findings on cytologic evaluation in- myoma, mast cell tumor, adenocarcinoma, clude increased percentage of nondegenerative and squamous cell carcinoma neutrophils and Curschmann’s spirals (airway b. Cats: Lymphoma and adenocarcinoma mucus) 358 SECTION II SMALL ANIMAL III. Bronchiectasis A. Cause and pathophysiology 1. Irreversible dilation of the airways typically accompanied by suppuration 2. Possible causes include chronic inflammation (e.g., bronchitis, foreign body), smoke inhala- tion, and primary ciliary dyskinesia 3. Dilated airways lack normal mucociliary clear- ance and trap secretions distally B. Clinical signs 1. Dogs are primarily affected. Rarely occurs in cats 2. History usually includes chronic productive cough, failure to respond to standard therapy, and sometimes hemoptysis 3. Physical examination may reveal fever and ab- normal lung sounds, such as crackles and in- Figure 25-1 Lateral thoracic radiograph of a middle-aged dog with creased bronchial sounds. Normal lung sounds chronic cough attributable to bronchitis. A striking bronchial pattern well may be absent with lung consolidation seen overlying the heart is present as a result of thickened bronchial C. Diagnosis walls. (From Thrall DE. Textbook of Veterinary Diagnostic Radiology, 5th ed. 1. CBC may indicate inflammation St Louis, 2007, Saunders.) 2. Thoracic radiography may show airway dila- tion and lung consolidation but is not sensitive 3. CT may demonstrate increased airway space 6. Airway samples should be submitted to aerobic with thickened airway wall and is more sensitive culture and Mycoplasma culture. The presence 4. Bronchoscopy can be very useful for the diag- of oral contaminants on cytology (e.g., squa- nosis and may show the dilated airway, red- mous cells or Simonsiella bacteria) makes a pos- dening of the mucosa, and accumulation of itive culture result of questionable importance mucus or pus D. Treatment 5. Cytologic evaluation of BAL fluids typically 1. General treatment includes weight reduction shows increased number of neutrophils and for overweight dogs, environmental control sometimes intracellular bacteria. Both aerobic (e.g., smoke, dust, heat) when possible, and and anaerobic cultures should be obtained airway humidification (steam inhalation or 6. Electron microscopy on biopsies of tracheal ep- nebulization) ithelium is used to diagnose ciliary dyskinesia 2. Antiinflammatory drugs are required to D. Treatment decrease airway inflammation. Prednisone is 1. General therapy with nebulization, chest coup- usually given at a dose of 0.5 to 1.0 mg/kg age, and postural drainage may assist in the every 12 hours for 5 to 7 days, and then the removal of secretions from the airways dose is tailored according to the response. 2. Antibiotic treatment should be based on cul- Infection should be ruled out before predni- ture and sensitivity results. Long-term treat- sone is administered ment may be required 3. Bronchodilators may be helpful in reducing 3. Lung lobectomy should be considered in cases clinical signs through reduction of work of of focal bronchiectasis breathing and stimulation of mucociliary clear- E. Prognosis: There is continued increased risk for ance. -agonists (e.g., terbutaline, albuterol) infection in most cases are more effective compared with theophylline. IV. Feline bronchial disease The dose of theophylline should be reduced if A. Cause and pathophysiology administered with enrofloxacin because enro- 1. An inflammatory process within the airways floxacin inhibits its metabolism results in mucosal edema, increased bronchial 4. Antitussives should be used to suppress cough mucus, and reversible bronchoconstriction if no infection is present and most of the 2. The cause is not identified in most cases. inflammation and secretions are resolved Associations with Mycoplasma, Aelurostrongylus 5. Antibiotics are warranted when secondary in- abstrusus, and Dirofilaria immitis have been fection has been documented. Doxycycline is a proposed in some affected cats good first choice pending culture results. How- 3. Cats with bronchial disease are thought to ever, infection is not a common component of have hyper-responsive airways the disease B. Clinical signs E. Prognosis 1. There is no gender or age predilection. 1. This is a chronic disease Siamese cats may be more sensitive 2. Goals of therapy are to control the degree of 2. A cat may present with a long-term history of inflammation and clinical signs and early diag- coughing, gagging, and lethargy or with an acute nosis and treatment of secondary infections episode of respiratory distress and cyanosis  CHAPTER 25 Respiratory Disorders 359 3. On physical examination, prolonged expiration 2. Exposure to a variety of insults can initiate a and decreased thoracic compliance may be chronic progressive inflammatory process, evident in some cats. Thoracic auscultation which may lead to diffusion impairment, lung may reveal wheezes or crackles. Open-mouthed fibrosis, and eventually end-stage restrictive breathing and cyanosis occur in an acute lung disease episode B. Clinical signs C. Diagnosis 1. Small-breed dogs, especially West Highland 1. CBC may reveal eosinophilia in some cats. white terriers may be at increased risk Fecal examination to detect parasitic infection 2. History typically includes shortness of breath and heartworm testing are indicated in and exercise intolerance. Episodes of syncope endemic areas may occur 2. Typical thoracic radiographic findings include 3. Physical examination may reveal tachypnea an interstitial peribronchial pattern with and sometimes cyanosis. Typical findings on “doughnuts” and “tram lines.” Additional auscultation are diffuse inspiratory crackles. findings may include lung hyperinflation, Split-second heart sound may be evident when patchy alveolar pattern, or lung consolidation. pulmonary hypertension develops Normal radiographs do not rule out the C. Diagnosis diagnosis 1. Thoracic radiographs usually show diffuse in- 3. Bronchoscopy can reveal mucus accumulation terstitial pattern but may be normal or plugging and nodular irregularities 2. BAL cytology shows increased percentage 4. Cytologic evaluation of airway fluids obtained of neutrophils but no mucus. Cultures are by endotracheal washing or bronchoscopy can negative include eosinophilic, neutrophilic, or mixed in- 3. Pathology of lung tissue shows interstitial flammatory responses. (Normal cats may have fibrosis in cats and increased collagen in West as much as 25% eosinophils on cytology) Highland white terriers, with no inflammation 5. Culture of airway fluids is warranted when D. Treatment there is evidence of infection on cytology. 1. Decrease exposure to possible triggers and Cultures of many healthy cats are positive for control weight Mycoplasma spp. 2. Prednisone at antiinflammatory to 6. Pulmonary function tests indicate higher immunosuppressive doses may result in airway resistance improvement D. Treatment 3. A trial therapy with bronchodilators may be 1. Emergency therapy considered a. Minimize stress E. Prognosis is guarded b. Administer a bronchodilator (e.g., terbuta- VI. Bronchopneumonia of infectious origin line, albuterol) subcutaneously or through A. Causes an inhaler 1. Pulmonary infections are common. Most cases c. If there is no immediate improvement, are of bacterial origin administer short-acting parenteral 2. Infection is typically by inhalation. The hema- corticosteroids togenous route is less common 2. Chronic management 3. Predisposition for bacterial pneumonia is a. Antiinflammatory drugs are the mainstay of present in many cases, including ITB, chronic therapy. A high dose of prednisolone is bronchitis, aspiration of oral or GI content given for several days and then tapered from vomiting or laryngeal paralysis, immuno- according to the clinical response. Alterna- suppression, foreign body tively, long-acting steroid injections or B. Clinical signs inhaled steroids may be used. Treatment 1. Typical signs include tachypnea, respiratory may be discontinued in 50% of the cats distress, productive cough, and fever. b. Oral bronchodilators (e.g., terbutaline, the- Mucopurulent nasal discharge may be ophylline) may help to control clinical signs present and decrease the dosage of corticosteroids 2. Auscultation reveals increased bronchial required sounds and crackles c. Control of environmental triggers (e.g., C. Diagnosis smoke, dust) may be beneficial in some 1. Typical findings of bacterial bronchopneumo- cases nia on thoracic radiographs include alveolar d. -blocker drugs can cause bronchoconstric- pattern with air bronchogram in a cranioven- tion and should be avoided tral distribution. Dorsocaudal pulmonary infil- E. Prognosis: The disease can be chronic with either trates are more likely to be caused by atypical persistent signs or recurrent episodes microorganisms (mycoplasmas, fungal V. Interstitial lung disease infections, mycobacteria) or hematogenous A. Causes and pathophysiology pneumonia 1. The cause is unknown and probably multifac- 2. CBC may reveal leukocytosis with a left shift or torial. Genetic factors may play a role neutropenia 360 SECTION II SMALL ANIMAL 3. Cytology of airway lavage demonstrates in- 2. Cytologic examination of BAL commonly creased numbers of degenerative neutrophils, reveals eosinophilic inflammation. Fungal often with intracellular bacteria. Culture is elements may be found with mycotic infections typically positive 3. Definitive diagnosis of noninfectious forms D. Treatment requires lung histopathology 1. Antibiotic treatment should be based on D. Treatment culture and sensitivity results 1. Treat pulmonary mycosis or heartworm infec- 2. Bronchodilator therapy (e.g., theophylline) tion when diagnosed may be beneficial 2. The noninfectious forms require immunosup- 3. Supportive therapy includes intravenous (IV) pressive therapy, including prednisone or a fluids, airway humidification, and coupage combination of cytotoxic drugs VII. Pulmonary infiltrates with eosinophils E. Prognosis is guarded A. Causes and pathophysiology IX. Noncardiogenic pulmonary edema 1. Lungworms, heartworms, larval migration, A. Causes and pathophysiology fungal infections and hypereosinophilic syn- 1. High-pressure edema is caused by overexpan- drome may be associated with accumulation sion of plasma volume or decreased oncotic of eosinophils in the lungs. Many cases are pressure that leads to fluid accumulation in idiopathic the lung 2. Eosinophils activation cause epithelial injury, 2. Permeability edema is caused by damage to leading to increased mucus and increased the alveolocapillary membrane that allows resistance to airflow protein-rich fluid to flood the alveoli (e.g., B. Clinical signs aspiration pneumonia, smoke inhalation, 1. History usually includes exercise intolerance, sepsis, and anaphylaxis) cough, and sometimes hemoptysis B. Clinical signs 2. Thoracic auscultation may reveal increased 1. History includes signs of tachypnea, bronchial sounds and diffuse coarse crackles respiratory distress, and cyanosis C. Diagnosis 2. Thoracic auscultation reveals fine crackles 1. CBC may show leukocytosis with eosinophilia C. Diagnosis and basophilia 1. Thoracic radiographs show patchy interstitial 2. Tests for heartworm, lungworm, and parasitic and alveolar pattern in the periphery and infections should be performed caudodorsal lung lobes 3. Thoracic radiographs typically show a mixed D. Treatment infiltrative pattern 1. Treat the primary disease 4. Bronchoscopy reveals hyperemic airways, 2. There is no specific therapy. Supportive with mucus. Polypoid proliferations on the treatment may include: Oxygen therapy, epithelium and bronchiectasis may be seen sedation, and mechanical ventilation. IV fluids 5. Cytology of airway fluid reveals increased and diuretics should be used with caution percentage of eosinophils X. Pulmonary thromboembolism D. Treatment A. Underlying causes include heartworm disease, 1. Removal of possible allergens and empiric pulmonary neoplasia, septicemia, amyloidosis, anthelmintic treatment are warranted hyperadrenocorticism, and immune-mediated 2. Immunosuppression glucocorticoid therapy is hemolysis required in most cases B. Clinical signs include dyspnea and right-sided VIII. Granulomatous pulmonary diseases heart failure A. Causes C. Radiographic findings include blunted pulmonary 1. Commonly associated with systemic fungal arteries and hypovascularity of the affected lung. infections in endemic regions However, abnormalities may be absent 2. Noninfectious forms include eosinophilic pul- D. Treatment is based on resolving the underlying monary granulomatosis, which is associated cause with heartworm infection and pulmonary lym- XI. Lung contusion phomatoid granulomatosis, which is probably A. Hemorrhage into the pulmonary parenchyma, a neoplastic condition most often caused by blunt thoracic trauma B. Clinical signs B. Clinical signs include acute dyspnea and possibly 1. Any age or breed may be affected shock from blood loss 2. History includes chronic respiratory distress, C. Diagnosis cough, and systemic signs 1. Auscultation may reveal crackles over a 3. Thoracic auscultation reveals wheezes and contused area or decreased lung sounds coarse crackles suggestive of lung consolidation or pleural C. Diagnosis effusion 1. CBC typically shows leukocytosis. Hyperglobu- 2. Thoracic radiographs typically reveal irregular linemia may be present. Thoracic radiographs patches of mixed interstitial-alveolar densities. reveal nodular pattern with hilar lymphade- Radiographic changes may be delayed for up nopathy to 24 hours  CHAPTER 25 Respiratory Disorders 361 D. Treatment C. Clinical signs 1. Transfusion of whole blood as indicated 1. Occur in older animals. Larger dogs may be 2. Administer oxygen if needed at increased risk. There is no sex or breed 3. Bronchodilators may improve ventilation predilection 4. Frequent repositioning of a recumbent animal 2. The most common clinical sign is chronic to prevent atelectasis cough. Dyspnea and weight loss may also oc- 5. Positive-pressure assisted ventilation may be cur. No signs may be apparent in some cases necessary in severe cases D. Diagnosis XII. Lungworms 1. Thoracic radiography usually reveals a mass A. Causes lesion. Evaluation of three views (ventrodorsal, 1. Aelurostrongylus abstrusus is a nematode that right lateral, and left lateral) is recommended. requires a snail as intermediate host and in- Up to 11% of pulmonary neoplasms might not fects cats when they eat transport hosts be detected in survey radiographs. CT or MRI (birds, small mammals, reptiles) may be useful to detect occult masses 2. Paragonimus kellicotti infects dogs and cats 2. Cytologic evaluation of sample obtained by by their ingestion of an intermediate host percutaneous transthoracic fine-needle aspira- (crayfish, aquatic snail) or by a transport host tion or airway lavage may detect neoplastic (e.g., raccoon) cells in some cases 3. Capillaria aerophilia infects dogs and cats by a 3. Lung biopsy obtained by bronchoscopy, thora- direct life cycle coscopy, or thoracotomy is usually required to 4. Crenosoma vulpis infrequently infects dogs confirm the diagnosis 5. Oslerus osleri forms granulomas near the tra- E. Treatment cheal bifurcation. Filaroides milksi is a bron- 1. Surgical excision of solitary masses is the chopulmonary parasite, and Filaroides hirthi is treatment of choice a lung parasite. These nematodes infect dogs 2. Adjunctive chemotherapy may improve by direct transmission survival in some cases B. Clinical signs 1. Signs are apparent most often in young DISORDERS OF THE THORACIC CAVITY animals that are heavily infested 2. Cough is the most common sign I. Thoracic wall trauma C. Diagnosis A. May be due to blunt or penetrating injuries 1. CBC may reveal eosinophilia B. Pain may lead to hypoventilation because the 2. Thoracic radiography findings may include in- animal is unwilling to breathe terstitial to granulomatous patterns. Air-filled C. A flail segment may be present when multiple cystic structures may appear with Paragonimus segmental rib fractures produce a free segment of infection thoracic wall, which moves inward during inspira- 3. Fecal flotation can identify ova (Capillaria, Par- tion and outward during expiration agonimus) or larva (Aelurostrongylus, Osleri, 1. Flail chest segments can initially be stabilized by Filaroides). Baermann technique may be positioning the animal with the flail side down required 2. Surgical stabilization may be required 4. Typical cytology findings of airway lavage in- D. Subcutaneous emphysema can occur with blunt clude eosinophilic infiltrate. Parasitic ova or or penetrating trauma. The condition is usually larva may be demonstrated self-limiting; treatment should be directed at the D. Treatment underlying cause 1. Fenbendazole is the safest antiparasitic drug II. Pneumothorax 2. Adjunctive treatment with prednisolone may A. Cause be beneficial in cases of severe eosinophilic 1. Traumatic pneumothorax is more common. pulmonary reaction Blunt trauma may cause pulmonary or bron- E. Prognosis is generally good unless severe granu- chial rupture and closed pneumothorax. Pene- lomatous disease has developed trating trauma through the thoracic wall XIII. Other respiratory parasites causes an open pneumothorax A. Dirofilaria immitis is found in the pulmonary 2. Spontaneous pneumothorax is caused by arteries, causing secondary pulmonary injury rupture of pulmonary blebs or bullae and is (see Chapter 12, Cardiovascular Disorders) considered primary when there is no evidence B. Toxoplasma gondii may cause pneumonia of underlying pulmonary disease. Secondary (see Chapter 18, Infectious Diseases) spontaneous pneumothorax is more common XIV. Pulmonary neoplasms and may occur with pulmonary abscesses, A. Carcinomas (bronchial, bronchoalveolar, or alveo- emphysema, neoplasia, pneumonia, or lar) are the most common primary lung tumors parasites in dogs. Metastatic rate at the time of diagnosis B. Clinical signs is high 1. Primary spontaneous pneumothorax B. Metastatic pulmonary neoplasms are more occurs most frequently in large, deep- common chested dogs 362 SECTION II SMALL ANIMAL 2. History of a traumatic event may be present C. Diagnosis with traumatic pneumothorax. History 1. Physical examination of previous respiratory signs may be a. Thoracic auscultation reveals muffled heart present with secondary spontaneous and lung sounds ventrally pneumothorax b. On percussion, the thorax sounds dull and 3. The animal presents with acute dyspnea, and hyporesonant shallow rapid respiration. Cyanosis may be 2. Thoracic radiography usually confirms pleural evident effusion. Signs include separation of the lung C. Diagnosis lobes from the parietal pleura and sternum and 1. Auscultation may reveal decreased heart and obscuring of the cardiac and diaphragmatic lung sounds. On percussion, the thoracic shadows cavity is hyperresonant 3. Thoracocentesis provides pleural fluids for 2. Thoracic radiograph findings may include ele- analysis and therapeutic drainage. The fluid vation of the heart off the sternum, collapse may be classified as transudate, modified of the lung lobes and retraction from the transudate, nonseptic exudate, septic exudate, chest wall, and a radiolucent area of free air chylous effusion, or hemorrhage (Figure 25-2) 4. Laboratory evaluation may provide useful D. Treatment information on the underlying cause 1. Open chest wounds should be covered 5. Ultrasonography of the thorax may confirm immediately the presence of pleural fluids and help in the 2. Thoracocentesis should be performed to diagnosis of some of the primary causes stabilize a dyspneic animal (e.g., mediastinal mass, diaphragmatic hernia, 3. Thoracostomy tube may be required if air cardiac disease) accumulates rapidly D. Pyothorax 4. Once the animal is stable, an underlying cause 1. Causes for spontaneous pneumothorax should be a. Accumulation of purulent exudate within considered the pleural space as a result of intrapleural III. Pleural effusion bacterial infection (septic pleuritis) or, A. An abnormal accumulation of fluid within the rarely, mycotic infection pleural space. It occurs when fluid formation is b. Mixed bacterial infections are most common, increased (e.g., increased capillary hydrostatic but entire anaerobic bacterial and fungal pressure), fluid absorption is decreased (e.g., infections may also occur decreased colloidal osmotic pressure), or pleural c. The source of infection in not identified in capillary permeability is increased (e.g., pleural most cases. Possible sources include pene- inflammation) trating chest wounds, perforations of medi- B. Clinical signs astinal structures (i.e., esophagus, trachea, 1. Dyspnea and exercise intolerance are the most bronchi), migrating foreign bodies (e.g., common signs grass awns), direct extension from the lung 2. The animal may prefer sitting or standing with in bacterial pneumonia, and hematogenic extended head and abducted elbows spread from distant infection 2. Clinical signs may include fever, depression, and anorexia, in addition to dyspnea 3. Diagnosis a. Hematologic findings typically include neu- trophilia with left shift and neutrophilic tox- icity. Neutropenia with a degenerative left shift may occur in severe cases b. Thoracic radiography findings are typical of pleural effusion c. Pleural fluid analysis reveals an opaque fluid with protein concentration greater than 4.5 g/dL and nuclear cell count greater than 50,000/ L (mostly degenerated neutrophils). Cytologic examination of the fluid reveals intracellular bacteria. Culture for aerobic and anaerobic bacteria should be performed 4. Treatment a. Antibiotic treatment is based on culture and Figure 25-2 Lateral radiograph of a dog with pneumothorax. Note sensitivity results and should last for at the apparent elevation of the heart from the sternum. (From Ettinger SJ, least 6 weeks Feldman EC, editors. Textbook of Veterinary Internal Medicine, 6th ed. b. Place thoracic tube to allow intermittent St Louis, 2005, Saunders.) drainage and lavage of the pleural cavity  CHAPTER 25 Respiratory Disorders 363 5. Complications include pleural adhesion and 4. Treatment pulmonary abscess formation and require a. Treat hypovolemic shock with IV fluids or thoracotomy to break the adhesions and blood transfusion remove diseased tissue b. Perform thoracentesis to relieve respiratory E. Chylothorax distress 1. Causes c. Consider exploratory thoracotomy for a. Accumulation of chyle in the pleural space animals that fail to stabilize b. The cause is unknown in most cases. Possi- G. Feline infectious peritonitis (see Chapter 18, ble causes include lymphangiectasia of in- Infectious Diseases) trathoracic lymphatics, traumatic rupture of H. Congestive heart failure (CHF) (see Chapter 12, the thoracic duct, intrathoracic neoplasia, Cardiovascular Disorders) cardiac disease, diaphragmatic hernia, I. Lung-lobe torsion lung lobe torsion, and vena caval 1. The mechanism is unknown. Lung-lobe torsion thromboembolism may be the cause or the result of the pleural c. Some breeds (Afghan hound, Shiba Inu, effusion Siamese and Himalayan cats) are predis- 2. Clinical signs are typical of pleural effusion posed to idiopathic chylothorax 3. Diagnosis 2. Clinical signs often include coughing in a. Thoracic radiography after thoracocentesis addition to typical signs of pleural effusion reveals a consolidated lung lobe 3. Diagnosis b. Pleural fluid analysis may vary a. Chylous effusion is characterized by higher c. Ultrasonography may be helpful to identify triglyceride and lower or equal cholesterol lung-lobe torsion concentrations compared with the serum. d. Confirmation of the diagnosis requires Pleural fluid cholesterol-to-triglyceride ratio thoracotomy in many cases is less than 1 4. Treatment is by lung lobectomy b. Cytologic examination of pleural fluids J. Thymic branchial cysts reveals mostly small lymphocytes 1. Multicystic masses in the cranial mediastinum. c. An underlying cause should be considered Develop from vestiges of the fetal branchial 4. Medical treatment arch system. Usually cause pleural effusion a. Treat any underlying cause. Traumatic 2. Pleural fluid may be modified transudate or thoracic duct rupture is treated by periodic nonseptic exudates pleural drainage and rest 3. Treatment is by surgical resection b. A fat-restricted diet supplemented with K. Diaphragmatic hernia medium-chain triglycerides that has been 1. May be complicated by pleural effusion, which recommended in the past is not effective is usually a modified transudate, but may be clinically blood or chyle in some cases c. Administration of rutin may be beneficial, 2. See soft tissue surgery section for further dis- but clinical results are inconsistent cussion 5. Surgical treatment is indicated if no underlying L. Pancreatitis-associated effusion medically treatable cause is found 1. Mild transient pleural effusion may occur with a. Ligation of the thoracic duct at the level of acute pancreatitis the diaphragm. Partial pericardectomy may 2. The pathogenesis is not fully understood improve the success rate of the procedure 3. Usually self-limiting b. Pleuroperitoneal shunting may be per- M. Pulmonary thromboembolism formed in refractory cases 1. Pleural effusion may occur whenever pulmonary c. Pleurodesis (using tetracycline or sterile thromboembolism is extensive enough to pro- talc) may be palliative in some cases duce infarction and ischemic necrosis of the lung 6. Complications include development of chronic 2. The effusion is usually a modified transudate fibrosing pleuritis. Surgical decortication or nonseptic exudate (removal of the layer of fibrin and fibrotic 3. Treatment involves managing the underlying reaction covering the visceral pleura) is cause and drainage of the pleural effusion indicated to avoid excessive pleural fibrosis N. Intrathoracic neoplasia F. Hemothorax 1. Neoplastic pleural effusion is caused by hemolym- 1. Accumulation of blood within the pleural phatic obstruction. Common causes include medi- space may be caused by thoracic trauma, astinal lymphoma and thymoma, primary and met- ruptured thoracic neoplasia, disorders of astatic pulmonary neoplasia, and mesothelioma hemostasis, or lung lobe torsion 2. Diagnosis 2. Clinical signs include shock due to blood loss a. Thoracic radiography and ultrasonography and dyspnea due to pleural effusion may reveal a mass in addition to pleural fluids 3. Diagnosis b. The fluid may be classified as modified a. Thoracic auscultation and percussion are transudate, nonseptic exudates, or chyle typical for pleural effusion 3. Treatment involves drainage of the pleural ef- b. Thoracentesis yields nonclotting blood fusion and treating the underlying neoplasia