Diagnostic evaluation of the respiratory tract (Proceedings)
Definitive diagnosis of pulmonary disease remains elusive at times. Cytological or histopathological samples are useful to help better classify the underlying cause as well as determine both prognosis and treatment course. Thus, it is prudent for the criticalist to have a strong grasp of the various techniques and options available for sampling. Additionally, as many patients with cardiopulmonary disease are relatively unstable, it is wise to recognize the potential risk and benefits of the testing.
The goal of the presentation is to describe the techniques as well as the potential benefits and risks of available methods to assess lung pathology. Available techniques include oral examination with biopsy, bronchoscopy, bronchoalveolar lavage, transtracheal aspirate, transoral tracheal aspirate, fine needle lung aspirate (with or without ultrasound guidance), and thoracocentesis with evaluation of cytological characteristics of the pleural effusion.
As an overview, pulmonary disease is classically localized to upper airway, tracheal/bronchial (lower airway), pulmonary parenchyma and pleural space. Differential diagnoses will vary based upon patient signalment and history. Some patients may require extensive evaluations, while others do not require further evaluation short of a complete history and physical examination. For example, a young dog with pulmonary infiltrates in a pattern consistent with pulmonary contusion after having been hit by a car requires no further diagnostic tests. Conversely, an older dog with a recurrent bout of cough and pulmonary infiltrate may require extensive testing.Larynx
Common laryngeal diseases include laryngitis (from excessive barking or tracheobronchitis) or laryngeal masses. Laryngeal masses are more common in older patients, particularly cats. Clinical signs of laryngeal masses include slowly progressive loud or stridorous breathing. Some animals have an apparent response associated with prior therapy associated with antibiotics or glucocorticoids. Neoplasia, specifically squamous cell carcinoma is the most common. A granulomatous proliferative (albeit non-neoplastic) condition has also been described in cats.
Biopsy samples are required to definitively identify neoplasia as well as to provide major prognostic information. Two points are of specific importance when considering a laryngeal biopsy. The first point is that all clinically significant obstruction laryngeal disease is not a quick "cure. This is important from the perspective of the client as in contrast with some other disease processes, the presence of laryngeal mass carries a very guarded prognosis. The second major point is that due to the often gradual progression of infiltrative disease, there is often a very tiny remaining airway lumen at the time of oral examination. Any loss of active airway dilating activity may result in complete airway occlusion. Thus, the clinician should be prepared for an emergency tracheostomy with readily available support staff and supplies. Additionally, even in the airway is likely considered adequate to recover the pet from sedation; airway swelling subsequent to a biopsy may result in occlusion. Discussion of a temporary tracheostomy tube should be cleared with the pet's family prior to undertaking an oral examination.
A laryngeal biopsy may be obtained with endoscopy biopsy instruments, long-handled scissor (Metzenbaums) or a biopsy cup forcep. My preference is to use a large cup forcep with the goal to also debulk a major portion of the mass.