abdominal compartment syndrome occurs when the abdominal cavity (compartment) within the body becomes subject to increased pressure from within. this may be caused by internal bleeding, a blockage or fluid build-up in the intestines, or 'ascites' which is when fluid accumulates in the peritoneal cavity - the space between the lining of the abdomen (peritoneum) and the abdominal organs (the stomach, small and large intestines, pancreas, liver, and gallbladder).