Secondary peritonitis has several major causes. Bacteria may enter the peritoneum via a hole (perforation) in the gastrointestinal tract, which can be caused by a ruptured appendix, stomach ulcer or perforated colon. The condition can also occur when pancreatic enzymes leak into the peritoneum during pancreatitis or when bile leaks from the biliary tract due to injury because these chemicals can irritate the peritoneum.

Foreign contaminants can also cause secondary peritonitis if they get into the peritoneal cavity. This can occur during use of peritoneal dialysis catheters

Inflammation of peritoneal cavity caused by bacteria can result in infection of the bloodstream (sepsis) and severe illness.

Secondary peritonitis can also affect premature babies who have necrotizing enterocolitis.