The Serum Ascites Albumin Gradient (SAAG) is a widely accepted method for classifying the cause of ascites, which is the accumulation of fluid within the peritoneal cavity. Ascites can result from a broad range of conditions including liver cirrhosis, heart failure, malignancy, and infections like tuberculosis. Correctly identifying the cause is critical because management strategies differ significantly depending on the underlying etiology.

The principle behind SAAG is based on the relationship between serum albumin and ascitic fluid albumin levels, which reflect portal pressure. When portal hypertension is present, as commonly seen in cirrhosis or congestive heart failure, the serum-ascitic gradient becomes elevated. A SAAG value ≥1.1 g/dL has been shown to strongly correlate with portal hypertension, with high sensitivity and specificity. Conversely, a value <1.1 g/dL suggests that portal pressure is not the driving factor, and causes such as malignancy, pancreatitis, nephrotic syndrome, or peritoneal infections should be considered.

SAAG has become a preferred diagnostic marker because it is more reliable than older methods, such as classifying ascitic fluid as “exudative” or “transudative” based on total protein levels. By directly relating fluid characteristics to hemodynamic changes, it provides better diagnostic accuracy. Clinicians use SAAG in conjunction with other laboratory, imaging, and clinical findings to make informed decisions about patient care.