CHAPTER 25. Respiratory Disorders
Michal Mazaki-Tovi
DIAGNOSTIC METHODS FOR RESPIRATORY DISEASES
I. Upper respiratory tract
A. Nasal cavity diseases
1. History
a. Sneezing and nasal discharge are the common clinical signs. Gagging, reversed sneezing, or stertor may occur when the disease extends to the nasopharynx
b. History should include the duration of clinical signs, the type and site of involvement of nasal discharge (unilateral or bilateral)
2. Physical examination
a. Sedation or anesthesia is usually required
b. Evaluate for asymmetry of the face, palate, or eyes, areas of pain, patency of the nasal passages, and damaged teeth
3. Laboratory testing
a. Complete blood cell count (CBC), serum biochemical profile, and coagulation tests are warranted when a systemic disease is suspected
b. Serologic tests may be used in the diagnosis of mycotic rhinitis, but false-negative results are common
4. Imaging
a. Skull radiography requires general anesthesia. Radiographic views include open-mouth ventrodorsal, occlusal, rostral-caudal frontal skyline, lateral, and oblique
b. Skull and nasal computed tomography (CT) may be used to delineate the extent of a mass, bone lysis, and accumulation of fluids
c. Magnetic resonance imaging (MRI) may be used for better definition of brain involvement
5. Nasal flushing for cytology and biopsy
a. Aggressive nasal flushing is required to yield sufficient tissue material
b. Submit samples for cytology and histopathology
6. Rhinoscopy
a. Requires general anesthesia
b. Allows visualization of mucosal lesions, masses, or foreign bodies
c. Samples for histopathology, cytology, culture, and sensitivity can be obtained with direct visualization
7. Surgical biopsy may be obtained by exploratory rhinotomy
B. Laryngeal diseases
1. History usually includes slowly progressive signs, such as change of voice and inspiratory stridor. Cyanosis and syncope may occur with laryngeal obstruction
2. Physical examination
a. Auscultation can detect upper respiratory inspiratory stridor
b. Palpation of the laryngeal area may detect pain, or asymmetry
3. Laryngoscopy and bronchoscopy
a. Evaluate pharyngeal structures, soft palate, and laryngeal movement with the patient under light anesthesia
b. Endoscopic biopsy, aspiration, or brush cytology may be performed
4. Diagnostic imaging
a. Laryngeal radiography may reveal elongated soft palate, fractures, or emphysema
b. Ultrasonography may demonstrate laryngeal paralysis
5. Electromyography
a. Neuromuscular, immune-mediated, and hypothyroidism-related laryngeal disorders may be associated with abnormal studies of the laryngeal muscles
b. Histopathology may be helpful in the diagnosis of masses or polyneuropathy
C. Tracheal diseases
1. History
a. Chronic, nonproductive, “honking” cough is a typical sign
b. Inspiratory dyspnea may be present with cervical tracheal collapse and expiratory dyspnea with intrathoracic collapse
2. Physical examination
a. Tracheal palpation may produce cough and detect sharp tracheal edges
b. Perform cardiac examination and auscultate the entire respiratory tract to differentiate the cough from other causes such as cardiac or lower respiratory disorders
3. Radiography
a. Both inspiratory and expiratory radiographs may be required to demonstrate collapsing trachea
b. Fluoroscopy allows dynamic evaluation of the trachea
5. Tracheoscopy may be helpful to visualize tracheal collapse, parasitic granulomas, foreign bodies, or neoplasia
II. Bronchopulmonary and pleural diseases
A. History
1. Typical signs include coughing, tachypnea, dyspnea, and exercise intolerance
2. Determine the duration of signs, the quality of the cough (productive or nonproductive), the time of day of the cough (cardiac cough is usually nocturnal), travel history (infectious diseases), and the presence of other signs (systemic disease)
B. Physical examination
1. Observe the pattern of breathing: Slow, deep breathing with inspiratory difficulty may indicate obstructive upper airway disease; short, shallow breathing may be associated with restrictive disease
2. Thoracic auscultation may reveal adventitious sounds, such as crackles (small airway or parenchymal disease), rhonchi (airway disease or exudate), and wheezes (airway obstruction)
3. Thoracic percussion may yield dull resonance (fluid or mass lesions within the pleural space or lung) or increased resonance (air)
C. Thoracic imaging
1. Determine the type of pattern present (interstitial, alveolar, bronchial, or vascular) and distribution of the lesions (localized or diffuse; cranial or caudal; and ventral, dorsal, or hilar)
2. Thoracic ultrasound may be helpful for detection of small amounts of fluid, consolidated areas of lung and mediastinal masses
3. CT may detect smaller pulmonary and pleural lesions
D. CBC and serum chemistry
1. CBC findings may include leukocytosis (inflammation, infection), eosinophilia (parasitic or allergic disease), polycythemia (chronic hypoxemia), or nucleated red blood cells (acute hypoxemia)
2. Serum biochemistry findings may indicate the presence of systemic disease
E. Arterial blood gas (ABG)
1. An arterial blood sample is usually drawn from dorsal pedal artery or femoral artery
2. ABG analysis evaluates the animal’s ability to oxygenate arterial blood. In the normal patient breathing room air, the partial pressure of oxygen should be >95 mm Hg. Elevations in CO 2 indicate ventilatory failure
F. Bronchoscopy allows direct visualization of the lower airway
G. Airway wash
1. Warm sterile saline is instilled in the lower respiratory tract and then retrieved. Samples are submitted for cytology and culture and sensitivity analyses
2. Transtracheal wash is performed in larger dogs. A through-the-needle catheter is inserted percutaneously under local anesthesia between the tracheal rings or through the cricothyroid membrane and then advanced into the lower airway
3. Endotracheal wash is performed in cats and small dogs. A catheter is inserted through a sterile endotracheal tube and then advanced into the lower airway
4. Bronchoalveolar lavage (BAL) may be performed during bronchoscopy and allows retrieving airway fluid sample from the lower airways
H. Lung biopsy
1. Indicated when the cause of a diffuse lung disease cannot be determined by less invasive methods
2. May be obtained by fine-needle aspiration, during bronchoscopy, using ultrasound or CT guidance, during thoracotomy (keyhole biopsy), or during thoracosopy
I. Thoracocentesis is performed to obtain fluid for analysis for diagnosis of pleural effusion
NASAL CAVITY AND SINUSES
I. Congenital diseases
A. Primary ciliary dyskinesia
1. Uncoordinated and ineffective ciliary function resulting in rhinitis, bronchitis, bronchiectasis, and bronchopneumonia
2. When associated with situs inversus, the clinical syndrome is known as Kartagener syndrome
3. Clinical signs include nasal discharge and coughing that begin at an early age
4. Diagnosis
a. Measuring the velocity of mucus clearance by using a drop of labeled macroaggregated albumin
b. Analysis of cilia by electron microscopy
5. Treatment is based on antibiotic therapy to treat secondary infections
6. Prognosis is guarded
B. Cleft palate (see Chapter 27)
II. Rhinitis and sinusitis of infectious origin
A. Causes
1. Dogs: Parainfluenza, distemper, adenovirus-2, Bordetella bronchiseptica, Aspergillus flavum, Penicillium spp., Rhinosporidium seeberi
2. Cats: Herpesvirus, calicivirus, Chlamydia psittaci, Bordetella bronchiseptica, Cryptococcus neoformans
3. Chronic rhinitis is often associated with another predisposing problem such as immunosuppression, foreign body, or tumor
B. History
1. Acute viral rhinitis is usually self-limiting unless immunosuppression is present
2. Primary bacterial rhinitis occurs with Bordetella bronchiseptica infection. Other bacterial nasal infections are usually secondary
C. Clinical signs
1. Typical signs include sneezing and nasal discharge. Gagging or retching may occur due to postnasal drip
2. Reversed sneezing may occur with nasopharyngeal involvement
D. Diagnosis
1. Dogs
a. Serologic tests for aspergillosis and polymerase chain reaction (PCR) for Bartonella
b. Imaging includes open-mouth radiographs or CT of the nasal cavity
c. Rhinoscopy may reveal a foreign body, a mass lesion, turbinate destruction, secretions
d. Histologic examination of nasal tissue is required for detection of hyphae of Aspergillus. Culture may be positive in normal dogs
e. Bacterial culture of mucosal biopsies may be more indicative of infection. Culture of nasal secretions may be positive in normal dogs
2. Cats
a. Serologic tests for feline immunodeficiency virus, feline leukemia virus, and Cryptococcus
b. Cytology from a nasal swab for detection of Cryptococcus
c. Tests for herpesvirus diagnosis (immunofluorescence, PCR).
d. If empiric treatment fails, perform imaging, rhinoscopy, and biopsy
E. Treatment
1. Viral
a. Supportive care and broad-spectrum antibiotic treatment
b. Lysine may be tried if herpesvirus infection is suspected
2. Bacterial
a. Doxycycline is effective against B. bronchiseptica or Bartonella infections, and clindamycin has some efficacy against Mycoplasma
b. Treat underlying disorder (e.g., foreign body, tooth root abscess)
3. Fungal
a. Aspergillus flavus and Penicillium spp. are most commonly treated with nasal tubes for intranasal administration of clotrimazole or eniconazole. Oral therapy with ketoconazole, itraconazole, or thiabendazole is generally less effective
b. Rhinosporidium granulomas can be treated by surgical extraction
c. Cryptococcus neoformans infection is treated with fluconazole, itraconazole, ketoconazole, or amphotericin B (alone or in combination with flucytosine)
III. Nasal parasites
A. Cuterebra, Eucoleus boehmi (nasal nematode), Pneumonyssus caninum (nasal mite)
B. Clinical signs include sneezing, nasal discharge, and reversed sneezing
C. Diagnosis is typically accomplished by direct visualization. E. boehmi is diagnosed by mucosal biopsy or identification of the ova on a fecal examination
D. Treatment is by manual removal of large parasites or by treatment with oral ivermectin.
IV. Allergic rhinitis
A. Presumed to occur in dogs and cats
B. Immunoglobulin E based rhinitis has not been demonstrated yet
V. Nasopharyngeal polyps
A. Inflammatory masses that arise from the epithelium of the nasopharynx. Commonly occur in cats
B. Voice change is a common early sign. Gagging may also occur
C. Otoscopic examination may reveal discharge and polypoid masses within the external ear canal. Oropharyngeal examination may demonstrate the polyp by retraction of the soft palate
D. Skull radiographs or CT may reveal increased density of one of the bullae or cranial to the pharynx
E. Treatment
1. Removal of the mass by traction
2. Ventral bulla osteotomy is indicated for removal of the inflammatory tissue when the middle ear is involved
VI. Foreign body
A. Common in young dogs; grass awns and other plant material especially common
B. Signs include sneezing and nasal discharge
C. Plants material is usually not visualized on radiographs
D. Rhinoscopy allows visualization and removal of the foreign body in most cases
VII. Neoplasms of the nasal cavity and paranasal sinuses
A. In dogs, carcinomas are most common, followed by sarcomas. Transmissible venereal tumors are uncommon but should be considered in endemic areas. Plasma cell tumors, mast cell tumors, and benign tumors occur rarely
B. In cats, nasal and paranasal lymphomas are most common, followed by adenocarcinoma and squamous cell carcinoma. Benign nasopharyngeal inflammatory polyps are common
C. Malignant nasal tumors usually are locally invasive, with metastasis occurring late in the course of the disease
D. Clinical signs
1. Nasal tumors are more common in older animals. Dolichocephalic and large-breed dogs are predisposed. There is no sex predilection
2. Common clinical signs include sneezing, nasal discharge, and epistaxis. Facial deformity occurs most commonly with skeletal neoplasms. Seizures, blindness, and behavioral changes may result from invasion to the central nervous system
E. Diagnosis
1. Radiography of the nasal cavity and paranasal sinuses may demonstrate loss of trabecular pattern, increase in soft tissue density, and septal destruction. Thoracic radiographs may indicate the presence of distant metastasis
2. CT and MRI are useful for evaluating the extent of the tumor
3. Biopsy for histopathologic examination is required for diagnosis and may be acquired by a blind procedure, rhinoscopy, or rhinotomy
F. Treatment
1. Radiation therapy has been shown to increase survival time in dogs and cats
2. Surgical cytoreduction in combination with radiation is rarely indicated for malignant tumors. Surgery is the treatment of choice for nasal polyps
3. Chemotherapy is indicated for the treatment of lymphoma and transmissible venereal tumor
UPPER AIRWAY DISORDERS
I. Brachycephalic syndrome
A. Consists of congenital disorders including stenotic nares, elongated soft palate, and tracheal hypoplasia (English bulldogs) and consequently, laryngeal saccules eversion
B. Signs include characteristic stretor and snoring and occasionally exercise intolerance
C. On physical examination stenotic nares may be evident
D. Oropharyngeal examination may reveal soft palate overlapping on the epiglottis. Everted laryngeal saccules may be seen as oval mucosal masses lateral to vocal folds
E. Treatment
1. Nasal wedge resection
2. Staphylectomy
3. Laryngeal sacculectomy
II. Laryngeal collapse
A. Most commonly results from brachycephalic syndrome
B. Signs include stretor or stridor, dyspnea, and occasionally exercise intolerance
C. Oropharyngeal examination reveals apposition or overlap of the arytenoids cartilages
D. Treatment
1. Treat predisposing factors (brachycephalic syndrome)
2. If signs persist permanent tracheostomy may be necessary
III. Laryngeal paralysis
A. Diagnosed primarily in old, large-breed dogs
B. Interrupted innervation of the larynx results in failure of the arytenoids cartilages to abduct during inspiration
C. Congenital in some breeds (e.g., the Bouvier des Flandres). Might be associated with hypothyroidism or polyneuropathies. Many cases are idiopathic
D. Clinical signs include stridor, voice change, and intermittent dyspnea, exacerbated by exercise, stress, or high environmental temperature. Hyperthermia may occur
E. Oropharyngeal examination under light anesthesia confirms the diagnosis. The arytenoids cartilages are unable to abduct during inspiration. Laryngeal edema may be present
F. Treatment is by arytenoid lateralization
IV. Laryngeal neoplasms
A. Generally rare in dogs and cats. Malignant tumors are more common
B. Laryngeal tumors may be primary (e.g., squamous cell carcinoma, lymphoma, chondrosarcoma) or metastatic (e.g., thyroid carcinoma)
C. The most common clinical sign is inspiratory dyspnea
D. Diagnosis
1. Radiography may demonstrate laryngeal distortion
2. Laryngoscopic evaluation may reveal a mass
3. Diagnosis in confirmed by biopsy and histopathology
E. Treatment
1. Surgical excision may be curative for benign tumors
2. Radiotherapy and chemotherapy may be beneficial for some tumors
V. Tracheal stenosis
A. Usually results from traumatic tracheal injury (e.g., bite wounds, intubation)
B. Signs include dyspnea and less commonly cough
C. Thoracic radiographs demonstrate focal reduction of the tracheal lumen diameter
D. Tracheoscopy is useful for assessing the location and severity of the stenosis
E. Treatment is by removal of the stenotic segment by tracheal resection and anastamosis
VI. Tracheal collapse
A. Causes
1. In dogs, abnormalities in chondrogenesis (congenital, inherited, or related to dietary deficiencies) result in decreased turgidity of the tracheal ring. Collapse may be found at rest or may be dynamic, with cervical collapse found on inspiration and intrathoracic collapse on expiration. Collapse of smaller airways may be also present
2. In cats, obstructive upper airway masses may cause tracheal collapse
B. Pathophysiology
1. The trachea usually collapses in a dorsoventral orientation, causing trauma to the epithelial surface, mucus production, and perpetuation of cough
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