Definition: Peritoneal fluid is a normal, lubricating fluid found in the peritoneal cavity -- the space between the layers of tissue that line the belly's wall and the abdominal organs (such as the liver, spleen, gall bladder and stomach). The fluid is mostly water with electrolytes, antibodies, white blood cells and other biochemicals. The primary function of peritoneal fluid is to reduce the friction between the abdominal organs as they move around during digestion.
In a healthy person, there is normally a small amount of peritoneal fluid present in the peritoneal cavity. However, some problems in the body can cause excess fluid to accumulate in the cavity. This fluid is called ascitic fluid and leads to ascites, one of the complications of cirrhosis.