Serum-Ascites Albumin Gradient (SAAG) Calculator
Serum-Ascites Albumin Gradient (SAAG) Calculator
Calculate the serum-ascites albumin gradient, the test that has replaced the transudate/exudate split for classifying ascites.
Serum-Ascites Albumin Gradient (SAAG)
Serum albumin − ascitic albuminSerum albumin 3.2 g/dL, ascitic fluid albumin 0.9 g/dL
Formula
- serum albumin
- g/dL, drawn the same day as the paracentesis
- ascitic albumin
- g/dL, from the same paracentesis
- 1.1 g/dL
- the cut-off — at or above it, portal hypertension; below it, a non-portal cause
Worked example
Serum albumin 3.2 g/dL, ascitic fluid albumin 0.9 g/dL
3.2 − 0.9 = 2.30 g/dL
2.30 is above 1.1 g/dL — a high gradient consistent with portal hypertension
SAAG and its causes
| Gradient | Interpretation | Typical causes |
|---|---|---|
| < 1.1 g/dL | Low gradient — non-portal | Peritoneal carcinomatosis, tuberculous peritonitis, pancreatic ascites, nephrotic syndrome |
| ≥ 1.1 g/dL | High gradient — portal hypertension | Cirrhosis, heart failure, Budd-Chiari syndrome, portal vein thrombosis, alcoholic hepatitis |
Why SAAG replaced the transudate/exudate split
SAAG has replaced the older transudate/exudate classification for ascites because it performs far better — about 97% accurate in predicting portal hypertension, against a much less reliable performance for the exudate/transudate rule applied to peritoneal fluid.
A gradient of 1.1 g/dL or above indicates portal hypertension: cirrhosis is by far the commonest cause, with heart failure, Budd-Chiari syndrome, portal vein thrombosis and alcoholic hepatitis making up most of the rest. A gradient below 1.1 g/dL points away from portal hypertension and toward peritoneal carcinomatosis, tuberculous peritonitis, pancreatic ascites or nephrotic syndrome.
The naming is counterintuitive and worth stating plainly: a HIGH gradient means portal hypertension, not a high ascitic protein or an inflammatory process — the opposite of how the word high usually reads in other fluid tests. Both bands above represent non-normal states, which is why neither is labelled normal here; the gradient tells you which category of disease is present, not whether ascites itself is benign.
Both samples must be drawn on the same day, ideally at the same paracentesis. Adding the ascitic total protein sharpens a high-gradient result further: a high SAAG combined with an ascitic protein above 2.5 g/dL suggests cardiac ascites rather than cirrhosis, where protein is typically lower.
Frequently asked questions
What is the serum-ascites albumin gradient?
Serum albumin minus ascitic fluid albumin, drawn from paired samples the same day. It classifies ascites by whether portal hypertension is present, and has replaced the older transudate/exudate split.
What does a high SAAG mean?
A gradient of 1.1 g/dL or above indicates portal hypertension, most often cirrhosis, but also heart failure, Budd-Chiari syndrome, portal vein thrombosis or alcoholic hepatitis.
Why is a HIGH gradient the abnormal-sounding one 'portal hypertension' result?
The naming is counterintuitive by design — a high gradient means a large albumin difference, which happens when portal pressure pushes fluid low in protein into the peritoneum. A low gradient means the ascitic fluid protein is closer to serum, which happens in inflammatory and malignant causes.
How does ascitic protein refine a high SAAG result?
A high SAAG with ascitic protein above 2.5 g/dL points to cardiac ascites rather than cirrhosis, since cirrhotic ascites typically has a lower protein content.
Related calculators
References
- Runyon BA, Montano AA, Akriviadis EA et al. The serum-ascites albumin gradient is superior to the exudate-transudate concept in the differential diagnosis of ascites. Ann Intern Med. 1992;117(3):215–20.
- Runyon BA. Management of adult patients with ascites due to cirrhosis. Hepatology. 2013;57(4):1651–3.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.