Radiology Procedures: Paracentesis (Establishing Etiology With The Serum-Ascites Albumin Gradient, SAAG)

OVERVIEW

Analyzing the fluid sent from a paracentesis can have much diagnostic utility, especially because in many instances the indication of the paracentesis is to to uncover why a patient has ascites.

The SAAG can be useful in helping make the diagnosis of what is causing the ascites (image source).

One of the initial characterizations of the ascites fluid that can be made to help diagnose the underlying cause of the ascites is the serum-ascites albumin gradient (SAAG). This page will discuss a bit more about how this gradient is calculated and its significance.

HOW IS THE SAAG CALCULATED?

The calculation of the SAAG is actually quite simple, and literally refers to the difference between the concentration of the albumin in the serum and the ascites. To calculate it, after the serum albumin value and ascites albumin values are calculated by the lab (in g/dL) the albumin concentration in the ascites will be subtracted from the serum albumin.

Here is a online calculator from MD Calc that will help make this calculation.

A SAAG of > 1.1 g/dL signifies that the albumin concentration in the in the ascites is LOW, and suggests a specific differential with regards to the underlying diagnosis.

SAAG of < 1.1 g/dL signifies that the albumin concentration in the in the ascites is HIGH, and suggests a different differential with regards to the underlying diagnosis.

WHAT DOES LOW SAAG (< 1.1 g/dL) MEAN?

A low SAAG means that the albumin concentration in the ascites is high relative to the serum concentration. Most clearly this suggests that portal hypertension is NOT  responsible for the patient’s ascites and that other diagnosis should strongly be considered.

WHAT DOES HIGH SAAG (> 1.1 g/dL) MEAN?

A high SAAG means that the albumin concentration in the ascites lis low relative to the serum concentration. Most clearly this suggests that portal hypertension like is the cause of the patient’s ascites.

 

Page Updated: 09.01.2019