Think of low SAAG (<1.1) as being almost similar to serum. Why would the ascitic fluid be almost similar to serum. The blood vessels are leaky! Think cancers, pancreatitis etc.
High SAAG (>1.1) means not similar to serum. Meaning the ascitic fluid has substantially low albumin as compared to serum. What organ in your body makes sure of that? Liver! Liver sinusoids are designed to keep albumin in blood vessel to the lymph that liver produces is very very albumin poor even when everything is working well. It just so happens that liver is producing a lot of that lymph!! Why? Cirrhosis and CHF physiology.