Ultrasound reveals a large amount of simple, anechoic fluid within the peritoneal cavity surrounding a small, irregular liver and within Morrison's pouch. This may be transudative, exudative, blood, pus or other organic juices. The most common cause of simple ascites is hepatic failure, frequently due to alcoholic cirrhosis.
Gravity causes fluid to flow along the peritoneal reflections and pool in the pelvis.
In the recumbent position, fluid flows cephalad into the right paracolic gutter and collects in the subhepatic and subphrenic spaces. On the left side, flow is limited by the phrenocolic ligament. In massive ascites, the liver, spleen and bowel are displaces medially and toward the center of the abdomen.