Question: A 55 year old female presents with new-onset ascites. She has a history of rheumatic fever as a child, hypertension, hypothyroidism, cholecystectomy and drinks 1-2 beers on most nights of the week. Diagnostic paracentesis is performed: WBC count 175, total protein 3.1, albumin 2.0 (serum albumin 3.7). What do you recommend?
A. stop the alcohol, this is probably cirrhosis
B. thyroid studies
C. cardiac evaluation
D. begin diuretics and send her home
Answer: When working up new-onset ascites, always have the pretest probability of portal hypertension in mind, as this is by far the most common cause of ascites. When cirrhosis is present, the serum-ascites albumin gradient (SAAG) should be >1.1. However, a SAAG > 1.1 is also seen in cases of cardiogenic ascites, as with constrictive pericarditis or right-sided heart failure, severe tricuspid regurgitation etc.
To exclude cardiogenic etiologies, look towards the total protein in the ascites; an otherwise healthy liver will allow protein to seep right out from the sinusoids and into the ascites ( > 2.5). In contrast, when the liver is cirrhotic, the perisinusoidal fibrosis prevents free flow of protein into the ascites (and total protein will be <2.5).
In the above case, the SAAG is >1.1 and the total protein is >2.5. Cardiac causes should be ruled out. If the heart looks OK on echocardiography, then the cause is probably cirrhosis and portal hypertension. Remember, these number thresholds should always be interpreted with caution, they are often misleading.
To get another idea about how SAAG interpretation can be misleading, refer to the link below. In this article, SAAGs <1.1 can still end up being secondary to cirrhosis (which takes me back to my initial thought: always have the pretest probability in mind as you get ready to analyze ascitic fluid!).