A thirteen year old domestic shorthair presented to the Small Animal Internal Medicine service on April 22, 2008 for evaluation for a two-month history of decreasing appetite and weight loss. A physical exam detected a grade I/VI left-sided systolic murmur and abdominal ultrasound and thoracic radiographs found bi-cavitary effusion of the pleural and peritoneal spaces. Echocardiographic examination confirmed decreased diastolic function, mildly decreased fractional shortening, and a mitral valve restrictive pattern, leading to a diagnosis of restrictive cardiomyopathy. Furosemide, enalapril, and pimobendan were prescribed to manage the bi-cavitary effusion and reduce workload on the myocardium, with instructions to recheck renal chemistry values the following week.