Ascitic Fluid Analysis and SAAG

Explanation

The serum-ascites albumin gradient is calculated by subtracting the ascitic albumin from the simultaneous serum albumin, and here it is 1.6 g/dL. A gradient of 1.1 g/dL or more indicates portal hypertension with about 97% accuracy, while a gradient below 1.1 g/dL points to peritoneal disease such as tuberculosis, carcinomatosis, pancreatitis or nephrotic syndrome. The ascitic total protein then separates the two main causes of high-gradient ascites: a total protein of 2.5 g/dL or more indicates post-sinusoidal or cardiac congestion, in which the hepatic sinusoids remain intact and leak protein-rich fluid, whereas a total protein below 2.5 g/dL indicates sinusoidal cirrhosis, where capillarisation of the sinusoids produces protein-poor fluid. This patient has a high gradient with a high total protein of 3.5 g/dL alongside raised jugular venous pressure, a third heart sound and pulmonary crackles, so cardiac ascites from congestive heart failure is the diagnosis, and treatment is directed at the heart failure with diuresis and afterload reduction rather than at the liver. Cirrhosis would give the same high gradient but a low ascitic protein, and there are no peripheral stigmata of chronic liver disease. Peritoneal tuberculosis and carcinomatosis both cause a low gradient below 1.1 g/dL with high protein, and are supported by lymphocytosis with raised adenosine deaminase or by positive cytology, neither of which is present. A polymorphonuclear count of 250/mm³ or more would indicate spontaneous bacterial peritonitis, which is excluded here at 60/mm³. Constrictive pericarditis and Budd-Chiari syndrome produce a similar high-gradient, high-protein picture and belong in the differential of cardiac-type ascites.

Why each option

A.

Peritoneal tuberculosis produces a low gradient below 1.1 g/dL with lymphocyte predominance and raised adenosine deaminase.

B.

Cirrhosis also gives a high gradient but the ascitic total protein is characteristically below 2.5 g/dL, and stigmata of chronic liver disease are absent here.

C.

Correct. A serum-ascites albumin gradient of 1.6 g/dL with an ascitic total protein above 2.5 g/dL indicates cardiac congestion, consistent with the raised jugular venous pressure and third heart sound.

D.

Peritoneal carcinomatosis produces a low gradient with positive cytology, whereas this patient has a high gradient and negative cytology.

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