Ever wondered what the hell is SAAG and what is the implication? What is a transudate and what is an exudate? This is an attempt to clarify some fundas of Ascites and it's differentials.
Ascites implies collection of fluid within the peritoneal cavity.
Atleast 1000 ml should be present to be detectable by Percussion.
USG Abdomen can detect as less as 100 ml!!
WHAT IS SAAG?
Serum : Ascites Albumin Gradient is a highly specific indicator of the cause of Ascites.
It is a ratio of Albumin in Serum : Albumin in Ascitic Fluid.
So what, you ask me?
A low SAAG would mean that Albumin is HIGHER IN ASCITIC FLUID than in serum. And poof! You jump to the conclusion that a Low SAAG indicates Exudate and vice - versa.
STOP
THIS IS NOT SO!!
A LOW SAAG ( 95% cases.
Conversely, a HIGH SAAG ( > 1.1 ) only implies that in > 95% cases, ASCITES IS DUE TO PORTAL HYPERTENSION!!
CONFUSED?? Ok. Just dont try to equate SAAG with exudate and transudate, just accept it on it's face value i.e. :-
SAAG 1.1 = Portal HTN.
Now let us proceed with this in mind.
STEP # 1 PARACENTESIS
Is a must in ALL CASES OF ASCITES.
50- 100 ml of fluid is withdrawn.
STEP # 2 ESTIMATE SAAG
STEP # 3
a) HIGH SAAG i.e. > 1.1
Implies Portal HTN, the causes being :-
RIGHT SIDED HEART FAILURE
- Proteins = 15-53 g/L (i.e either transudate/ exudate)
- Confirm Diag by ECHO/ CARDIAC CATH
CIRRHOSIS
- Transudate ( 1000/ microliter
Confirmed by = DIAGNOSTIC LAPAROSCOPY & BIOPSY
TUBERCULAR PERITONITS
- Hemorrhagic/ Straw colored/ Chlyous Fluid
+
- Exudate
+
-Predominant Lymhocytes, WBCs > 1000/microliter
Confirmed by Peritoneal Biopsy and Culture
PANCREATIC ASCITES
-Mostly Exudative
+
- Presence of Amylase in Ascitic Fluid
Confirmed by ERCP / CT Scan
NEPHROTIC SYNDROME
- TRANSUDATE is seen.
Confirmed by DERANGED RFTs
So, in a nutshell, SAAG SHOULD NOT BE INTERPRETED AS TRANSUDATE / EXUDATE.
- The only cause of HIGH SAAG WITH EXUDATIVE FLUID - RIGHT SIDED HEART FAILURE.
- The only cause of LOW SAAG WITH TRANSUDATIVE FLUID - NEPHROTIC SYNDROME.
Hope this article helped in clearing your fundas!!
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