Collection and interpretation of respiratory cytology

Advances in pulmonary cytological sampling have helped establish a more accurate diagnosis and better therapeutic choices for the respiratory patient. Choosing the appropriate test is necessary to maximize the potential diagnostic yield and should be based on the clinical presentation of the patient as well as the minimum database. This article describes several methods of collection of cytological samples for the canine and feline upper and lower respiratory tracts, defines normal respiratory cytology, and discusses normal cytological characterization of various respiratory diseases. Categorization of cytological findings may aid the clinician in narrowing the potential etiologies for the pulmonary disorder. The authors focus on cytological recovery and analysis from transtracheal wash (TTW), bronchial brushing, transthoracic lung aspiration (TTLA), bronchoalveolar lavage (BAL), and open chest biopsy. Indications, complications, and contraindications for each procedure are discussed. Variation in expected findings among BAL, TTW, TTLA, and bronchial brushings are described. Appropriate sampling technique, transport, and processing are also emphasized.