Diagnostic Methods in Respiratory Disease

Chapter 158 Diagnostic Methods in Respiratory Disease



Larry Berkwitt, James C. Prueter


This chapter briefly considers some of the more important diagnostic methods used in the recognition and assessment of respiratory disease with the goal of reminding the clinician of potential studies that may be of use in the diagnosis of upper and lower respiratory tract diseases.



UPPER RESPIRATORY TRACT



Nasal Cavity Diseases


Sneezing and nasal discharge are the principal clinical problems associated with nasal cavity and sinus diseases. A number of infectious diseases can be responsible (see Chapter 163 for additional information and diagnostic pointers). Inflammation, parasites, exudate, foreign bodies, or tumors may extend into the nasopharynx leading to gagging, reversed sneezing, or stertor. Diagnosis can be simple or highly challenging.



History


When taking the history, include:



• The chronology, progression, and duration of clinical signs, such as sneezing

• Type of nasal discharge

• Site of involvement (unilateral or bilateral)


Sneezing



• Acute paroxysmal sneezing typically is associated with viral rhinitis, nasal foreign body, allergic rhinitis, or trauma.

• Chronic sneezing suggests neoplasia, parasites, prolonged infection or inflammation (e.g., fungal rhinitis), chronic foreign body, or trauma with secondary infection or osteomyelitis.

• Reversed sneezing is a sign of disease or inflammation in the nasopharynx. Mites, post-nasal drip, foreign bodies, follicular rhinitis, and neoplasms are associated with this sign. When no lesions are evident, it is likely that (idiopathic) nasopharyngeal spasm is the cause.


Nasal Discharge



• Serous discharge typically is associated with acute foreign body, allergy, and viral infection.

• Mucopurulent and/or serosanguineous discharge typically is associated with viral infections (complicated by bacteria); bacterial, mycotic, and parasitic infections; long-term foreign body; neoplasia; and lymphocytic-plasmacytic inflammation.

• Hemorrhagic discharges suggest trauma, neoplasia, coagulopathy, and prolonged infection.

• Foodstuffs in the discharge suggest a communicating congenital defect (cleft palate) or acquired oro-nasal fistula.


Duration of Clinical Signs



• Sudden onset of signs suggests foreign body, viral infection, trauma, or coagulopathy.

• Chronic signs are associated with neoplasia, infection, foreign body, parasite infection, chronic inflammation, or congenital defect.


Site of Involvement



• Unilateral discharge suggests early neoplasia, foreign body, early infection, dental disease, or trauma.

• Bilateral discharge suggests chronic infection or inflammation, chronic foreign body with resulting infection/osteomyelitis, advanced neoplasia, coagulopathy, pneumonia, parasites, allergy, or trauma.


Physical Examination


A complete physical examination includes a thorough evaluation of the oral cavity, mucous membranes, tonsils, hard and soft palate, retropharyngeal area, regional lymph nodes, and teeth. Heavy sedation and/or anesthesia are generally required if the nasal cavity, nasopharynx, or larynx will be examined (see below).


• Identify swelling and asymmetry of the face, palate, or eyes (exophthalmos) that might suggest neoplasia, fungal infection, or trauma.

• Identify areas of pain that may localize the disorder.

• Evaluate for loss of patency of one or both nasal passages.

• Note ocular discharge that may be associated with nasolacrimal duct inflammation and/or obstruction secondary to inflammation or neoplasia.

• Identify cracked, loose, and infected teeth.


Complete Blood Count (CBC), Serum Chemical Profile, and Coagulation Screen


These evaluations are important when systemic diseases may be an underlying cause of signs. Although clotting disorders can cause epistaxis, it is far more commonly associated with platelet disorders such as immunemediated thrombocytopenia, von Willebrand’s disease, thrombocytopathia (drug-related or from hyperglobulinemia), or ehrlichiosis.



Serology



• Serologic tests such as immunodiffusion and enzyme-linked immunosorbent assay (ELISA) for aspergillosis and penicilliosis antibodies and for cryptococcal capsular antigen can be used for diagnosis of mycotic rhinitis. However, false-negative results are common, limiting the usefulness of serology. Molecular methods of diagnosis, confined to reference laboratories, are used for agents such as Bartonella spp.

• Direct observation, cytology, culture, and biopsy are more reliable than serology for identifying nasal fungi.


Radiography



• General anesthesia is essential for proper positioning and for prevention of motion artifacts.

• Include the following radiographic views (see Chapter 4):
• Open-mouth ventrodorsal projection

• Intraoral (occlusal)

• Rostral-caudal frontal skyline

• Lateral

• Oblique skull views, particularly if dental arcade problems are suspected


Computed Tomography (CT) and Magnetic Resonance Imaging (MRI)



• Use CT of the nasal cavity and skull to delineate the extent of masses, loss of turbinates, bony lysis, midline shifts, or accumulation of fluid.

• Use MRI for better definition of brain involvement from invading nasal tumors (see Chapter 125).


Nasal Flushing for Cytology and Biopsy of Nasal Tissue


Nasal cytologic evaluation is often of little or no value unless it is performed with aggressive nasal flushing or by rhinoscopic visualization with the animal under anesthesia. Biopsy samples can be obtained under direct visualization, or by a blind method, guided by results of clinical examination and imaging. Retrograde rhinoscopy is needed to biopsy caudal masses or lesions extending into the nasopharynx.


• Perform aggressive nasal flushing with a polypropylene (rigid) male urinary catheter. Measure the length (nares to medial canthus) prior to insertion to avoid penetrating past the cribriform plate.
• Perform intermittent flushing and suctioning via syringe to obtain as much nasal fluid and/or tissue fragments as possible.

• Place gauze sponges in the nasal pharynx to catch any tissues that may be extracted during the flushing procedure.

• Submit samples for culture, cytology, and histopathology.

• Small and medium-sized clamshell forceps can be used to obtain biopsy samples with or without benefit of rhinoscopy.


Rhinoscopy


Rhinoscopic examination under anesthesia allows visualization of mucosal lesions, masses, or foreign bodies. Biopsy and procurement of specimens for cytology, culture, and sensitivity can be guided by direct visualization. Different instruments are often used to evaluate the nostrils and cranial nasal cavity versus the posterior choane and nasopharynx (the passage located dorsal to the hard and soft palate). A flexible scope is superior for retrograde rhinoscopy, though it may be possible to evaluate the nasopharynx with a dental mirror, spay hook (to pull the soft palate cranioventrally), and a bright light. Polyps in cats are often visible simply by pulling the soft palate forward. Instrumentation for rhinoscopy can include any of the following:


• A flexible cytoscope or rhinoscope with an outer diameter of 2 mm is preferred.

• An otoscope with bright light source may be used for antegrade rhinoscopy.

• An arthroscope or cystoscope with an outer diameter of 1.9 to 5 mm will be useful in larger dogs.

• A bronchoscope with an outer diameter of 2.9 to 5 mm will be useful in larger dogs.

• Flexible pediatric bronchoscope.


Surgical Biopsy



• Exploratory rhinotomy with removal of a bone flap (see Chapter 160) provides complete exposure of the nasal cavity for biopsy, foreign body retrieval, culture, and debridement of diseased tissue.

• Drainage tubes can be placed at the time of surgery for treatment of bacterial and/or fungal infections.


Laryngeal Diseases



History


Clinical signs of laryngeal disease often are slowly progressive, and the owner may have noted them for an extended period of time. Laryngeal paralysis is common in a number of breeds (see Chapter 161).


• The owner may report hoarseness, progressive changes in voice, or complete loss of voice.

• Noisy respirations characterized by high-pitched inspiratory stridor or by mild, raspy, or fluid-sounding noise are common.

• Choking, gagging, and coughing may be observed, particularly while the animal is eating and/or drinking. This often worsens as the disease progresses or if there is concurrent pharyngeal disease.

• Exercise intolerance, cyanosis, and syncope may be observed in patients with laryngeal obstruction (e.g., laryngeal collapse, paralysis, foreign body, or neoplasia). Problems are exacerbated in high heat and humidity.


Physical Findings



• The most common physical findings in laryngeal disease are inspiratory dyspnea and stridor. Auscultation can detect upper respiratory inspiratory stridor (“wheeze”) or lower-pitched obstructive sounds centered over the larynx.

• Palpation of the laryngeal area may detect the site of pain, fractures, and subcutaneous emphysema in cases of trauma and asymmetry due to neoplasia, granulomas, laryngitis, or unilateral muscle atrophy.

• The gag reflex may be decreased in some cases of laryngeal paralysis.


Laryngoscopy/Bronchoscopy



• Perform direct visualization under a light plane of anesthesia for evaluation of pharyngeal structures, soft palate, and laryngeal motor function. Tiletamine HCl/zolazepam HCl (Telazol) can cause laryngeal paralysis, so another form of sedation should be used. Propofol also depresses laryngeal motion. The use of doxapram has been advocated to stimulate the respiratory center to decrease the number of false positive examinations.

• Observe laryngeal (arytenoid) movement during both phases of respiration. Often asymmetry is observed between the left and right arytenoids and vocal folds. Be certain not to confuse passive abduction during expiration with active movements.

• A bronchoscope allows the best evaluation of the pharynx and the subglottic area for masses, infiltrates (areas of discoloration), granulomas, and polyps. In cats, laryngeal paralysis is often related to invasion by a neoplasm.

• Aspiration or brush cytology and endoscopic biopsy may be performed at the time of examination, if appropriate. Following laryngeal biopsy, the patient should be closely observed, as postsurgical edema or hemorrhage at the biopsy site may result in airway obstruction.

Related posts:

  1. Feline Infectious Peritonitis (Feline Coronavirus)
  2. Borreliosis (Lyme Disease)
  3. Immune-Mediated Dermatoses
  4. Otitis Media and Otitis Interna

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Diagnostic Methods in Respiratory Disease

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