Diagnosis
A definitive diagnosis of CCB is premised on radiographs and bronchoscopy with cytol- ogy/culture (Rozanski 2014; Ristic and Herrtage 2001). The typical signalment of dogs with CCB is older small breed dogs, who are also at risk for a number of other diseases such as tracheal collapse, myxomatous mitral valve disease (MMVD), and canine hyperadrenocorticism; which may complicate the diagnosis and treatment.
It is not uncommon that a patient is presented with a cough and the veterinarian detects a heart murmur during a physical examination with possible scenarios being primary respiratory disease with an incidental cardiac murmur; or primary respiratory disease and pulmonary hypertension, resulting in right sided heart disease; or MMVD with cardiomegaly and a cardiac cough. The presence of a slow heart rate with a sinus rhythm tends to negate heart disease as a possible cause for the cough. In addition, it has been demonstrated that congestive heart failure (CHF) is not a common cause of coughing in MMVD, while left atrial enlargement is. Resultantly, a cardiac cough, is most likely due to pressure on the left main stem bronchus, due to increased atrial pressure. Thus it may be possible from a thorough physical examination and radiographs to differentiate between MMVD and CCB. Alternatively, pro-BNP is a useful biomarker to exclude cardiac disease as a cause of coughing and dyspnea (Oyama 2015; Prosek et al. 2007). Furthermore, since glucocorticoids are often the mainstay of therapy, it must be remembered that these patients are also at risk for developing hyper- adrenocorticism, given the age and breeds normally affected by CCB. Therefore, along with the fact that patients require anesthesia if a definitive diagnosis is to be reached, a complete blood count, urinalysis, fecal flotation (for lung worm), heart worm antigen (if indicated), and serum biochemistry should be performed. Echocardiography is useful to screen for pulmonary hypertension, which can cause, or contribute to coughing. This will allow a comprehensive stratification of the individual patient with regards to possible comorbid diseases, ensuring that the management is most successful. Furthermore, the clinician should remember that steroid therapy may alter the outcome of diagnostic tests (such as liver enzymes, platelets, and cytology) and therefore, once started may obscure the diagnosis of diseases such as liver disease, hyperadrenocorticism, and may mask cytological typical lesions on bronchio- alveolar lavage (BAL) fluid analysis.
More on the topic Diagnosis:
-
Veterinarian -