History
A 3-year-old spayed female domestic shorthair cat was evaluated for lethargy, inappetence, vomiting, and labored breathing. On initial examination, the cat was mildly febrile, dehydrated, and tachypneic with pronounced inspiratory effort and muffled heart sounds. A CBC, serum biochemical analysis, urinalysis, and bacterial culture and antimicrobial susceptibility testing of a urine sample revealed the following abnormalities: mild hyperbilirubinemia, moderate hyponatremia, moderate neutropenia, and severe lymphopenia. Results of FeLV and FIV tests were negative. Orthogonal radiographs of the thorax were obtained to evaluate for thoracic disease as an underlying cause for the cat's dyspnea (Figure 1).
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Diagnostic Imaging Findings and Interpretation
A severe generalized increase in the size of the cardiac silhouette is evident (Figure 2). Dorsal displacement of the thoracic portion of the trachea is present, and the cardiac silhouette spans 4.5 intercostal spaces on the lateral view. On the dorsoventral view, the cardiac silhouette occupies most of the thorax and has a globoid shape. Pleural fissure lines are best observed superimposed and dorsal to the cardiac silhouette on the dorsoventral view. Scalloping of the ventral lung margins is also present, and overlying pleural effusion obscures the caudal vena cava. Most likely differential diagnoses for the severe increase in size of the cardiac silhouette include pericardial effusion and dilated cardiomyopathy.
On echocardiography, cardiac structure and function appeared normal, but severe pericardial effusion was present (Figure 3). The pericardial effusion was echogenic, containing a large amount of amorphous material attached to the pericardium and left ventricular apex. Free-floating hyperechoic debris was also present in the pericardial effusion, and the pericardium appeared thickened. Cardiac tamponade causing right-sided heart failure and transfer of pericardial fluid to the pleural space were considered the most likely causes for this cat's pleural effusion.
Comments
Pericardiocentesis was performed to remove 95 mL of thick, red fluid with flecks of white debris from the pericardial sac. Aerobic bacterial culture and antimicrobial susceptibility testing of the fluid revealed a mixed population of an Enterobacteriaceae sp and coagulase-negative Staphylococcus sp. The cat was medically managed with broad-spectrum antimicrobials for 8 weeks and required an additional therapeutic pericardiocentesis prior to hospital discharge because of recurrent pericardial effusion 24 hours following the initial pericardiocentesis. At 9 weeks, no abnormalities were detected on physical examination or echocardiography.
Pericardial effusion should be high on the list of differential diagnoses when a severely enlarged, globoid cardiac silhouette is identified on radiographic views of the thorax. Although pericardial effusion in cats is often subclinical, it may represent a primary disease affecting the pericardium or it may occur secondary to other diseases, including cardiac disease, neoplasia, and infection.1 When pericardial effusion is severe, it may cause cardiac tamponade and secondary pleural effusion.2 On thoracic radiographs, cardiomegaly, pleural effusion, and abnormal pulmonary patterns are the most common findings in cats with pericardial effusion.3
This cat had a severe, bacterial pericardial effusion without primary cardiac disease. Interestingly 2 distinct bacterial populations were isolated from the pericardial effusion. It is possible that a septicemia consisting of both types of bacteria led to inoculation of the pericardial sac, although undetected direct inoculation via a penetrating wound or foreign body may represent a more likely scenario.
- 1.↑
Davidson BJ, Paling AC, Lahmers SL, et al. Disease association and clinical assessment of feline pericardial effusion. J Am Anim Hosp Assoc 2008;44:5–9.
- 2.↑
Zoia A, Hughes D, Connolly DJ. Pericardial effusion and cardiac tamponade in a cat with extranodal lymphoma. J Small Anim Pract 2004;45:467–471.
- 3.↑
Hall DJ, Shofer F, Meier CK, et al. Pericardial effusion in cats: a retrospective study of clinical findings and outcome in 146 cats. J Vet Intern Med 2007;21:1002–1007.