Distention of the abdomen is caused by a buildup of gas and intestinal contents proximal to the area of blockage. When the patency of the lumen is compromised, buildup of saliva, gastric juices, and biliary and pancreatic secretions occur along with electrolytes and serum proteins. As the bowel attempts to accommodate increasing pressure from the excess of fluid, abdominal distention and pain occur. Necrosis then begins as blood flow to the intestine is impaired. Peritonitis develops when intestinal contents are released into the abdomen as a result of increased pressure on the lumen.

Adhesions, which are bands of connective tissue that form after abdominal surgery, are the most common cause of intestinal obstruction. They can pull, twist, loop, or compress a section of bowel, causing an obstruction. Hernias develop when a loop of bowel protrudes through a weak abdominal wall. Inguinal hernias are common in men; femoral and umbilical hernias occur in both sexes. The peritoneum along with a loop of bowel is pushed through the opening, preventing the passage of abdominal contents. Stasis and edema increase the size of the loop, leaving it trapped or incarcerated and the blood supply threatened or compromised. When drainage leads to infarction of the bowel loop, it is said to be strangulated.