The most likely diagnosis is constrictive pericarditis. This patient has undergone previous cardiac surgery, which is a risk factor for constrictive pericarditis. Ascitic fluid analysis should include measurement of albumin and total protein; cell count and bacterial cultures should be checked when infection is suspected. The serum-ascites albumin gradient (SAAG) should be calculated by subtracting the ascitic fluid albumin level from the serum albumin level. The main factors that distinguish a cardiac source for ascites from other sources are a SAAG of 1.1 g/dL (11 g/L) or greater and an ascitic fluid total protein level of 2.5 g/dL (25 g/L) or greater. This patient meets these criteria, making a cardiac cause for his ascites likely. In addition, over 90% of patients with constrictive pericarditis have evidence of jugular venous distention and clear lungs on auscultation. Other less commonly observed findings include Kussmaul sign (rise in jugular pressure on inspiration), paradoxical pulse, and a pericardial knock on cardiac auscultation.

Patients with cirrhosis, portal hypertension, and resultant ascites will also have a SAAG greater than 1.1 g/dL (11 g/L), but the ascitic fluid total protein level will be less than 2.5 g/dL (25 g/L). Therefore, alcoholic and nonalcoholic cirrhosis are not the likely cause of this patient's ascites.

Tuberculous peritonitis is very uncommon and is associated with a SAAG less than 1.1 g/dL (11 g/L), an ascitic fluid total protein level greater than 3 g/dL (30 g/L), and a lymphocytic predominance in the cell count with differential. Although this patient has a high ascitic fluid total protein level, the SAAG is greater than 1.1 g/dL (11 g/L) and he does not have a predominance of lymphocytes on the ascitic fluid cell count.