MKSAP quiz: New-onset ascites with lower-extremity edema

What is the most likely cause of this 68-year-old man's ascites?

A 68-year-old man is evaluated for new-onset ascites with lower-extremity edema. Symptoms have increased gradually over the past 4 weeks. He has consumed three alcoholic beverages per day for many years. His medical history is notable for coronary artery bypass graft surgery 8 months ago and dyslipidemia. His medications are low-dose aspirin, atorvastatin, and metoprolol.

On physical examination, temperature is 36.8 °C (98.2 °F), blood pressure is 122/84 mm Hg, pulse rate is 64/min, and respiration rate is 16/min; BMI is 28. Cardiac examination reveals an elevated jugular venous pressure, a normal S1 and S2, and no murmurs. Pulmonary examination findings are normal. Abdominal examination reveals hepatomegaly, distention, dullness to percussion over the flanks, and a positive fluid wave. There is 2+ pitting edema of the lower extremities.

Laboratory studies reveal a serum albumin level of 3.5 g/dL (35 g/L). Other studies, including serum alanine aminotransferase and aspartate aminotransferase levels, are normal.

Paracentesis reveals a total nucleated cell count of 120/µL with 30% polymorphonucleocytes. Ascitic fluid albumin level is 2.3 g/dL (23 g/L) and total protein is 3.5 g/dL (35 g/L).

Which of the following is the most likely cause of this patient's ascites?

A. Alcoholic cirrhosis
B. Constrictive pericarditis
C. Nonalcoholic cirrhosis
D. Tuberculous peritonitis

MKSAP Answer and Critique

The correct answer is B. Constrictive pericarditis. This item is available to MKSAP 17 subscribers as item 3 in the Gastroenterology & Hepatology section. More information about MKSAP 17 is available online.

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.

Key Point

  • A serum-ascites albumin gradient (SAAG) of 1.1 g/dL (11 g/L) or greater with an ascitic fluid total protein level of 2.5 g/dL (25 g/L) or greater indicates a cardiac cause of ascites.