Final answer:
Ascites cause reduced intravascular volume by pulling fluid into the abdominal cavity, resulting in hypovolemia. This is exacerbated by lowered oncotic pressure due to liver dysfunction and increased hydrostatic pressure, which leads to the movement of fluids into interstitial spaces.
Step-by-step explanation:
Ascites lead to reduced intravascular volume due to the sequestration of fluid in the abdominal cavity, which causes a decrease in the effective circulating blood volume. When fluid accumulates in the ascitic space, it is pulled from the bloodstream, resulting in hypovolemia (low blood volume).
This condition is often associated with liver cirrhosis, where the inability of the liver to synthesize proteins, such as albumin, leads to reduced oncotic pressure in the blood vessels, which normally helps to retain fluid in the circulatory system. The lower oncotic pressure and increased hydrostatic pressure in blood vessels, particularly in the portal vein due to liver damage, collectively promote the movement of fluid out of the blood vessels into the interstitial space, causing edema and ascites.
Furthermore, ascites can compromise renal blood flow and function, triggering mechanisms that attempt to conserve salt and water, exacerbating the fluid shift into the interstitial spaces and the peritoneal cavity.