Dynamics of ascites formation in rats with experimental cirrhosis.

Renal function, sodium balance, and ascites formation were observed during induction in rats of experimental cirrhosis. The same variables were studied after partial removal of the ascites in rats with experimental cirrhosis. Glomerular filtration rate (GFR) and effective renal plasma flow (RPF) did not change during hepatic cirrhosis development. Positive sodium balance significantly higher than that observed in controls preceded the appearance of ascites for a period of about 2 wk. When the ascites was removed, GFR, RPF and positive Na balance did not change if Na intake remained constant. Ascites reformation rate was largely dependent on sodium balance. These data strongly support the "overflow" theory of ascites formation and are difficult to reconcile with the classical "underfilling" theory.