<aside> 📏 Serum-ascites albumin gradient (SAAG) = Albumin concentration of ascitic fluid - serum obtained on the same day.

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This gradient is physiologically based on oncotic-hydrostatic balance and is related directly to portal pressure.

1. High gradient (SAAG > 1.1 g/dL): Hydrostatic pressure imbalance
   • Portal HTN (non-peritoneal cause of ascites):
     • High SAAG, low protein (< 2.5 g/dL): Cirrhosis
     • High SAAG, high protein (≥ 2/5 g/dL): Budd-Chiari syndrome (hepatic vein obstruction), heart failure, portal vein thrombosis
2. Low gradient (SAAG < 1.1 g/dL): Oncotic pressure imbalance
   • Peritoneal cause of ascites:
     • Low SAAG, low protein (< 2.5 g/dL): Nephrotic syndrome
     • Low SAAG, high protein (≥ 2.5 g/dL): Peritoneal causes (peritoneal mesothelioma, peritoneal carcinomatosis, tuberculous peritonitis, fungal and parasitic infections, etc)