Question: Where does cirrhotic ascites originate?
A. dilated splanchnic circulation
B. hepatic sinusoids
C. peritoneal lymphatics
Answer: Maybe not as straightforward as you imagined! While more than one answer choice may be correct, the predominant source of ascites is the hepatic sinusoids, which are the smallest caliber blood vessels in the liver. The combination of advanced fibrosis and increased hepatic inflow (from the splanchnic circulation) combine to increase hydrostatic pressures enough to cause leakage into the peritoneal cavity.
Increased hydrostatic pressures within the splanchnic circulation, combined with decreased oncotic pressure (hypoalbuminemia) may also contribute to leakage and ascitic accumulation, but to a lesser degree.
And speaking of peritoneal cavity, its lymphatics can drain up to 900 mL of ascites daily, maintaining the patient’s ‘compensated’ phenotype. Any accumulation over 900 mL will cause ascites. As far as I know, varices do not contribute to cirrhotic ascites.