Learn/Interpretation

SAAG and Ascites Interpretation

The serum-ascites albumin gradient classifies ascites by mechanism with 97% accuracy — the first step toward understanding why a patient has fluid, whether it is infected, and how to prevent the next hospitalization.

  • Calculate the SAAG from serum and ascitic albumin values and interpret its diagnostic significance
  • Classify ascites as portal hypertension-related versus non-portal-hypertension-related using SAAG and ascitic protein
  • Apply an algorithmic approach to the workup and management of new-onset ascites
10 min · 5 sectionsInterpretationHigh-yield
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Enter simultaneous serum and ascitic albumin to calculate the SAAG. Both samples must be drawn at the same time — or within hours — for the result to be valid. Enable the traumatic-tap correction for bloody specimens before interpreting the PMN count.

Serum Albumin · Normal 3.5–5.0
g/dL · from serum
Ascites Albumin · Typically < 1.5
g/dL · from paracentesis
Enter both values to calculate SAAG
Why it matters
SAAG has replaced the exudate/transudate classification for ascites with ~97% accuracy for detecting portal hypertension. Inoculate 10 mL directly into aerobic & anaerobic blood-culture bottles at the bedside — this improves culture yield from ~50% to ~80%.
SAAG = serum albumin − ascitic albuminHigh SAAG ≥1.1 g/dLLow SAAG <1.1 g/dLPortal hypertension→ protein-poor transudatealbumin retained in serumPeritoneal disease→ protein-rich exudatealbumin leaks into ascitescirrhosis · cardiac · BCSmalignancy · TB · pancreatic

Why the gradient works: portal hypertension leaks protein-poor fluid (large gradient); peritoneal disease leaks protein-rich fluid (small gradient)

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Check your understanding
3-question self-test
Q1
A 58-year-old man with alcohol-associated cirrhosis is admitted for new-onset confusion. Diagnostic paracentesis: ascites albumin 0.6 g/dL, serum albumin 2.8 g/dL, PMN 320 cells/mm³, culture growing E. coli. What is the immediate next step?
Q2
A therapeutic paracentesis yields grossly bloody ascitic fluid. The lab reports RBC 120,000 cells/mm³ and a PMN count that crosses the SBP threshold of 250 cells/mm³. Which statement best describes the purpose of the traumatic tap correction taught on this page, and what does applying it prevent?
Q3
A 72-year-old man presents with new ascites and lower-extremity edema. Which ascitic fluid profile most strongly suggests cardiac ascites (CHF) rather than cirrhosis?
References
  1. 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):215-220. PubMed 1616215
  2. Biggins SW, Angeli P, Garcia-Tsao G, et al. Diagnosis, evaluation, and management of ascites, spontaneous bacterial peritonitis and hepatorenal syndrome: 2021 practice guidance by the American Association for the Study of Liver Diseases. Hepatology. 2021;74(2):1014-1048. PubMed 33942342
  3. Crabb DW, Im GY, Szabo G, et al. Diagnosis and treatment of alcohol-associated liver diseases: 2019 practice guidance from the American Association for the Study of Liver Diseases. Hepatology. 2020;71(1):306-333. PubMed 31314133
  4. Northup PG, Garcia-Pagan JC, Garcia-Tsao G, et al. Vascular liver disorders, portal vein thrombosis, and procedural bleeding in patients with liver disease: 2020 practice guidance by the American Association for the Study of Liver Diseases. Hepatology. 2021;73(1):366-413. PubMed 33219529
  5. Mohty M, Malard F, Abecassis M, et al. Revised diagnosis and severity criteria for sinusoidal obstruction syndrome/veno-occlusive disease in adult patients: a new classification from the European Society for Blood and Marrow Transplantation. Bone Marrow Transplant. 2016;51(7):906-912. PubMed 27183098
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  10. Gómez-Cerezo J, Barbado Cano A, Suárez I, et al. Pancreatic ascites: study of therapeutic options by analysis of case reports and case series between the years 1975 and 2000. Am J Gastroenterol. 2003;98(3):568-577. PubMed 12650789
  11. Silvey S, Patel N, Tsai SY, et al. Higher rate of spontaneous bacterial peritonitis recurrence with secondary spontaneous bacterial peritonitis prophylaxis compared with no prophylaxis in 2 national cirrhosis cohorts. Am J Gastroenterol. 2025;120(5):1066-1075. PubMed 39235290
  12. Prosty C, Noutsios D, Dubé LR, et al. Prophylactic antibiotics for upper gastrointestinal bleeding in patients with cirrhosis: a systematic review and Bayesian meta-analysis. JAMA Intern Med. 2025;185(10):1194-1203. PubMed 40788637