Pathophysiology
Clinical meaning
Ascites is the pathological accumulation of fluid within the peritoneal cavity, most commonly caused by portal hypertension in the setting of cirrhosis (accounting for approximately 85% of cases). Understanding the cellular and hemodynamic mechanisms underlying ascites formation is essential for effective nursing assessment and management. In cirrhosis, chronic hepatocyte injury from alcohol, viral hepatitis, or non-alcoholic steatohepatitis triggers hepatic stellate cell activation and progressive fibrosis. Fibrotic bands and regenerative nodules distort the hepatic architecture, increasing resistance to portal blood flow. Portal pressure rises from the normal gradient of 1 to 5 mmHg to above 10 to 12 mmHg (the threshold for ascites formation), a state called clinically significant portal hypertension. The increased portal pressure raises hydrostatic pressure in the splanchnic capillary bed, favoring fluid transudation into the peritoneal cavity. Simultaneously, portal hypertension induces splanchnic vasodilation through increased production of nitric oxide (NO), carbon monoxide, and endogenous cannabinoids by the splanchnic endothelium. This vasodilation reduces effective arterial blood volume (EABV), activating neurohormonal compensatory systems: the renin-angiotensin-aldosterone system (RAAS), the sympathetic nervous system (SNS), and non-osmotic release of antidiuretic hormone (ADH/vasopressin). These...