From the Guidelines
The Serum Ascitic Albumin Gradient (SAAG) is a diagnostic calculation used to determine the cause of ascites, calculated by subtracting the albumin concentration in the ascitic fluid from the albumin concentration in the serum, with a value ≥1.1 g/dL indicating portal hypertension as the cause of ascites. This calculation is crucial in distinguishing between portal hypertensive and non-portal hypertensive causes of ascites, guiding treatment strategies and improving patient outcomes 1. The SAAG is more accurate than the older exudate-transudate classification system because it directly reflects the pressure gradient between the portal venous system and the peritoneal cavity, providing valuable pathophysiological insight into the mechanism of ascites formation. Some key points to consider when interpreting SAAG results include:
- A SAAG value ≥1.1 g/dL indicates portal hypertension, commonly seen in conditions like cirrhosis, alcoholic hepatitis, heart failure, or Budd-Chiari syndrome 1.
- A SAAG value <1.1 g/dL suggests non-portal hypertension causes such as peritoneal carcinomatosis, tuberculosis, pancreatitis, or nephrotic syndrome 1.
- The SAAG should be calculated using blood and ascitic fluid samples collected simultaneously, with albumin levels measured in both 1.
- This test is essential for guiding appropriate treatment strategies for patients with ascites, including dietary sodium restriction and diuretic therapy 1.
From the Research
Definition of Serum Ascitic Albumin Gradient
- The Serum Ascitic Albumin Gradient (SAAG) is a parameter used to differentiate between causes of ascites, particularly to identify the presence or absence of portal hypertension 2.
- It is calculated as the difference between the albumin level in serum and ascitic fluid 3, 4, 5.
Clinical Significance of SAAG
- A high SAAG value (≥ 1.1 g/dL) indicates the presence of portal hypertension, which is often associated with liver disease, such as cirrhosis 2, 3, 5.
- A low SAAG value (< 1.1 g/dL) suggests the absence of portal hypertension and may indicate other causes of ascites, such as malignant neoplasm or nephrotic syndrome 2, 6.
- SAAG can be used to guide further investigations and management of patients with ascites 3, 4.
Relationship between SAAG and Portal Hypertension
- Studies have shown a significant correlation between SAAG and hepatic venous pressure gradient, indicating the reliability of SAAG in demonstrating the presence of portal hypertension 5.
- However, one study found that SAAG value is weakly related to the extent of portal hypertension in patients with liver cirrhosis, and its implication seems to be limited in clinics 4.