SAAG Calculator
Calculate the serum-ascites albumin gradient (SAAG) to differentiate causes of ascites — portal hypertension vs. peritoneal origin. Free medical diagnostic tool with clinical interpretation and charts.
About This Calculator
The SAAG (Serum-Ascites Albumin Gradient) Calculator is a medical diagnostic tool used by physicians and healthcare professionals to differentiate the underlying causes of ascites — abnormal fluid accumulation in the peritoneal cavity. By comparing albumin levels in blood serum and ascitic fluid, this calculator helps determine whether portal hypertension or a peritoneal condition is responsible.
The calculation follows the formula established by Paré, Talbot, and Hoefs (1983): SAAG = Serum Albumin − Ascitic Fluid Albumin. Both measurements must be taken simultaneously from the same patient. A SAAG value greater than 1.1 g/dL (11 g/L) indicates portal hypertension with 97% accuracy, while a value below 1.1 g/dL suggests a non-portal or peritoneal origin such as infection, malignancy, or pancreatitis.
The SAAG has largely replaced the older total protein-based classification of ascites (transudate vs. exudate) because it is more accurate in identifying portal hypertension. However, the ascitic fluid total protein (AFTP) measurement remains useful as a secondary parameter in the differential diagnosis of ascites.
Clinical Application
This tool is valuable for gastroenterologists, hepatologists, internal medicine physicians, and medical students evaluating patients with new-onset ascites. Common conditions associated with high-SAAG ascites (>1.1 g/dL) include liver cirrhosis, congestive heart failure, constrictive pericarditis, and Budd-Chiari syndrome. Low-SAAG ascites (<1.1 g/dL) is seen in peritoneal carcinomatosis, tuberculous peritonitis, pancreatic ascites, and nephrotic syndrome.
Frequently Asked Questions
What is the serum-ascites albumin gradient (SAAG)?
The serum-ascites albumin gradient (SAAG) is the difference between albumin concentration in blood serum and ascitic fluid. It helps physicians determine the underlying cause of ascites, particularly whether portal hypertension is involved.
How is SAAG calculated?
SAAG is calculated by subtracting the ascitic fluid albumin concentration from the serum albumin concentration: SAAG = Serum Albumin − Ascitic Fluid Albumin. Both values must be measured at the same time for accuracy.
What does a SAAG greater than 1.1 g/dL mean?
A SAAG value greater than 1.1 g/dL (11 g/L) indicates portal hypertension as the cause of ascites with 97% accuracy. This typically corresponds to transudative ascites seen in conditions like liver cirrhosis, heart failure, or Budd-Chiari syndrome.
What does a SAAG less than 1.1 g/dL mean?
A SAAG value less than 1.1 g/dL indicates a non-portal or peritoneal cause of ascites, such as peritonitis, pancreatitis, or malignancy. This corresponds to exudative ascites where inflammation of the peritoneum is the primary mechanism.
What is the difference between transudate and exudate?
Transudate is a protein-poor fluid that forms due to increased hydrostatic pressure or decreased oncotic pressure (e.g., in cirrhosis or heart failure). Exudate is a protein-rich fluid that leaks from inflamed blood vessel walls (e.g., in infections or malignancy). SAAG helps distinguish between the two.
What units does this calculator use?
This calculator uses grams per deciliter (g/dL) for albumin measurements. The SAAG threshold of 1.1 g/dL is equivalent to 11 g/L in SI units, and both values are displayed in the results.
Is this calculator a substitute for medical diagnosis?
No, this calculator is an educational and reference tool for healthcare professionals and students. It should not replace clinical judgement or a physician's assessment. Always consult a qualified healthcare provider for diagnosis and treatment.