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Serum-Ascites Albumin Gradient (SAAG)

SAAG = serum albumin − ascitic fluid albumin (same day). A SAAG ≥1.1 g/dL indicates portal hypertension (cirrhosis, heart failure, Budd-Chiari) with about 97% accuracy; <1.1 g/dL suggests non-portal causes (peritoneal carcinomatosis, TB, pancreatitis, nephrotic syndrome).

Serum albumin (g/dL or g/L)
Ascitic fluid albumin (g/dL or g/L)

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Interpretation

Result	Meaning
≥ 1.1 g/dL (11 g/L)	Portal hypertension
< 1.1 g/dL	Not portal hypertension

Formula

SAAG = serum albumin − ascitic fluid albumin (g/dL), samples drawn the same day

Clinical pearls

Add ascitic total protein: SAAG ≥1.1 with protein ≥2.5 g/dL suggests cardiac ascites or Budd-Chiari; with protein <2.5 g/dL, cirrhosis.
Mixed ascites (cirrhosis plus a second cause) still gives a high SAAG.
Serum albumin <1.1 g/dL or hyperglobulinaemia can falsely narrow the gradient.

Examples

saag serum albumin 3.0 ascitic albumin 1.0 serum ascites albumin gradient, serum alb 32 g/L, fluid alb 25 g/L is this portal hypertensive ascites: serum albumin 2.8, ascites albumin 0.9

FAQ

What does a SAAG of 1.1 or higher mean?

Portal hypertension is the cause of the ascites, most often cirrhosis; the test is about 97% accurate.

Is SAAG better than the exudate/transudate classification?

Yes. Runyon showed SAAG classifies ascites correctly far more often than total-protein-based exudate/transudate labels.

Evidence

Runyon BA et al. The serum-ascites albumin gradient is superior to the exudate-transudate concept in the differential diagnosis of ascites. Ann Intern Med 1992;117:215–20.

Hepatology & GI · Reviewed 2026-10-14 · Methodology