SAAG Calculator — Serum-Ascites Albumin Gradient
Calculate SAAG (Serum-Ascites Albumin Gradient) to distinguish portal hypertension-related ascites from other causes. A gradient ≥ 1.1 g/dL strongly suggests portal hypertension; below 1.1 g/dL points to non-portal aetiology.
g/dL
g/dL
Portal hypertension (SAAG ≥ 1.1 g/dL)
- 1
Serum albumin
3.5 g/dL - 2
SAAG
3.5 − 1.2 = 2.30A gradient ≥ 1.1 g/dL indicates portal hypertension.
How does this calculator work?
SAAG = serum albumin − ascites albumin (both in g/dL, drawn on the same day). A SAAG ≥ 1.1 g/dL indicates portal hypertension (cirrhosis, cardiac ascites, hepatic vein thrombosis) with ~97% sensitivity. A SAAG < 1.1 g/dL points to non-portal causes (peritoneal carcinomatosis, TB peritonitis, nephrotic syndrome). Clinical interpretation by a physician is required.
Formula
How this is calculated
Ascites — the pathological accumulation of fluid in the peritoneal cavity — has many causes, broadly divided into those driven by elevated portal venous pressure and those caused by other mechanisms. The Serum-Ascites Albumin Gradient (SAAG) exploits the oncotic-hydrostatic balance: in portal hypertension, elevated hydrostatic pressure drives protein-poor fluid into the peritoneum, so the ascitic albumin is much lower than the serum albumin, producing a large gradient. In non-portal conditions (malignancy, tuberculosis, nephrotic syndrome) the mechanism is different — exudative or protein-rich fluid leaks into the abdomen — and the gap between serum and ascites albumin is smaller.
A SAAG ≥ 1.1 g/dL has a sensitivity of ~97% and specificity of ~91% for portal hypertension as the underlying mechanism. Causes include cirrhosis (most common), alcoholic hepatitis, right-heart failure (cardiac ascites), massive hepatic metastasis, and portal or hepatic vein thrombosis. A SAAG < 1.1 g/dL suggests peritoneal carcinomatosis, tuberculous peritonitis, nephrotic syndrome, biliary or pancreatic ascites, or serositis.
SAAG must be calculated from serum and ascites samples drawn on the same day — albumin levels fluctuate, and a non-simultaneous pair invalidates the result. The SAAG has largely replaced the older exudate/transudate classification based on total protein, which was less accurate for portal hypertension.
Frequently asked questions
A SAAG ≥ 1.1 g/dL indicates ascites due to portal hypertension with about 97% sensitivity. The most common cause is liver cirrhosis. Values significantly above 1.1 (e.g. > 1.7) may suggest cardiac ascites, where the gradient is even wider due to the combination of portal hypertension and low oncotic pressure.
A SAAG < 1.1 g/dL makes portal hypertension unlikely, but cirrhosis without portal hypertension is rare — so yes, a low SAAG effectively argues against cirrhosis as the cause of ascites. In ambiguous cases, serum-ascites total protein, cytology, culture, adenosine deaminase (for TB) and imaging provide additional diagnostic information.
Serum albumin varies with nutrition, inflammation and fluid shifts. The SAAG calculation assumes both samples reflect albumin concentrations at the same moment, so that any difference is due to the gradient across the peritoneum rather than temporal variation in serum albumin. Even a few days between samples can invalidate the result.
Also known as
TG we-Calculate Editorial Team. (2026). SAAG Calculator — Serum-Ascites Albumin Gradient [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/saag-calculator
TG we-Calculate Editorial Team. "SAAG Calculator — Serum-Ascites Albumin Gradient." TG we-Calculate. 2026. https://we-calculate.com/calculator/saag-calculator.
TG we-Calculate Editorial Team, "SAAG Calculator — Serum-Ascites Albumin Gradient," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/saag-calculator
@misc{wecalculate_saag_calculator, title = {SAAG Calculator — Serum-Ascites Albumin Gradient}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/saag-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?