SERUM ASCITES ALBUMIN GRADIENT (SAAG)

The serum ascites albumin gradient (SAAG) has been proved to categorize ascites better than the total protein concentration or other parameters²¹ (Table 91-3). The SAAG is based on oncotic-hydrostatic balance. Portal hypertension results in an abnormally high hydrostatic pressure gradient between the portal bed and ascitic fluid. A similarly large difference must exist between ascitic fluid and intravascular oncotic forces. Albumin exerts a greater oncotic force per gram than that exerted by other proteins. Therefore, the difference between the serum and ascitic fluid albumin concentrations correlates directly with portal pressure.