What are the most common causes of a serum-ascites albumin gradient (SAAG) ≥ 1.1?

A serum-ascites albumin gradient (SAAG) of 1.1 g/dL or greater is primarily indicative of portal hypertension, which occurs due to underlying liver disease or conditions affecting blood flow. The most common causes associated with a SAAG ≥ 1.1 are cirrhosis and congestive heart failure.

Cirrhosis, a condition characterized by progressive liver fibrosis and disruption of normal hepatic architecture, leads to increased blood pressure in the portal venous system. This increase in pressure facilitates the transudation of fluid into the peritoneal cavity, resulting in ascites.

Similarly, congestive heart failure causes elevated pressure in the systemic venous system, which can lead to passive hepatic congestion and subsequently portal hypertension. The increased hydrostatic pressure in the hepatic vasculature can also result in fluid accumulation in the abdominal cavity.

In contrast, other conditions such as malignancy and infections typically present with a lower SAAG, indicating that the ascitic fluid is primarily due to exudative processes rather than transudates related to portal hypertension. Understanding the underlying pathophysiology of these conditions allows physicians to effectively interpret SAAG results and determine the most likely causes of ascites in their patients.