The Serum/Ascites Albumin Gradient (SAAG) test is a medical diagnostic tool that measures the difference in levels of albumin protein between the serum (blood plasma) and the ascitic fluid (fluid that accumulates in the abdominal cavity). The SAAG test is commonly used to determine the underlying cause of ascites, which can be caused by a variety of conditions such as liver disease, heart failure, or cancer. The SAAG value is calculated by subtracting the ascitic fluid albumin level from the serum albumin level, and a value of 1.1 g/dL or higher indicates that the ascites is likely due to portal hypertension, which is often associated with liver disease. A SAAG value of less than 1.1 g/dL suggests that the ascites is due to other causes such as cancer or inflammation. The SAAG test is a valuable tool in the diagnosis and management of patients with ascites.