What is the serum-ascitic albumin gradient (SAAG)?

From the Guidelines

The serum-ascites albumin gradient (SAAG) is a diagnostic tool used to differentiate the causes of ascites by measuring the difference between serum albumin and ascitic fluid albumin concentrations. To calculate SAAG, subtract the ascitic fluid albumin level from the serum albumin level, with both measurements taken on the same day. A SAAG value ≥1.1 g/dL indicates portal hypertension as the cause of ascites, commonly seen in conditions like cirrhosis, alcoholic hepatitis, heart failure, and Budd-Chiari syndrome. A SAAG value <1.1 g/dL suggests non-portal hypertension causes such as peritoneal carcinomatosis, tuberculosis, pancreatitis, or nephrotic syndrome. This test is more accurate than the older exudate-transudate classification system, with approximately 97% accuracy in identifying portal hypertension-related ascites, as supported by the most recent guidelines from the American Association for the Study of Liver Diseases 1. The physiological basis for this gradient relates to oncotic pressure differences between the portal venous system and the ascitic fluid, which directly correlates with portal pressure. SAAG remains a cornerstone in the initial evaluation of patients with ascites and helps guide appropriate treatment strategies.

Some key points to consider when interpreting SAAG results include:

• A high SAAG value (≥1.1 g/dL) is indicative of portal hypertension, which is often seen in cirrhosis, heart failure, and other conditions that affect the liver or portal venous system.
• A low SAAG value (<1.1 g/dL) suggests non-portal hypertension causes of ascites, such as peritoneal carcinomatosis, tuberculosis, or pancreatitis.
• The accuracy of SAAG in identifying portal hypertension-related ascites is approximately 97%, making it a valuable diagnostic tool in clinical practice, as noted in the guidelines from the American Association for the Study of Liver Diseases 1 and the Clinical Practice Guidelines for Liver Cirrhosis: Ascites and Related Complications 1.
• SAAG should be calculated using simultaneously obtained serum and ascitic fluid samples, as recommended by the guidelines from the American Association for the Study of Liver Diseases 1 and the Clinical Practice Guidelines for Liver Cirrhosis: Ascites and Related Complications 1.

Overall, SAAG is a useful diagnostic tool that can help clinicians differentiate between portal hypertension and non-portal hypertension causes of ascites, and guide appropriate treatment strategies, as supported by the most recent and highest quality evidence from the American Association for the Study of Liver Diseases 1 and other reputable sources.

From the Research

Definition of Serum Ascitic Albumin Gradient

• The serum-ascites albumin gradient (SAAG) is a diagnostic tool used to assess the cause of ascites, which is the accumulation of fluid in the peritoneal cavity 2.
• SAAG is calculated by subtracting the albumin concentration in the ascitic fluid from the albumin concentration in the serum.
• A high SAAG indicates portal hypertension, which is a common cause of ascites, while a low SAAG suggests other causes such as peritoneal carcinomatosis or tuberculous peritonitis.

Clinical Significance of SAAG

• The diagnostic evaluation of ascites involves determining the SAAG to identify the underlying cause of the condition 2.
• SAAG is used to differentiate between portal hypertensive and non-portal hypertensive causes of ascites.
• A SAAG of 1.1 g/dL or higher indicates portal hypertension with a high degree of accuracy.

Management of Ascites

• The management of ascites involves a combination of sodium restriction, diuretics, and other therapies such as large-volume paracentesis and transjugular intrahepatic portosystemic shunts 2, 3, 4.
• The choice of treatment depends on the underlying cause of ascites, the severity of the condition, and the presence of complications such as spontaneous bacterial peritonitis or hepatorenal syndrome.