Peritonitis is caused by a bacterial infection. The bacteria may originate from the bloodstream, or from infected organs inside the abdomen. The bacteria spread to the peritoneum and start to grow, which results in inflammation and severe pain.

Causes of peritonitis include:

• Abdominal injury
• Appendicitis
• Ascites
• Colitis
• Diverticulitis
• Gallbladder disease
• Intussusception
• Ischemic bowel disease
• Pancreatitis
• Pelvic inflammatory disease
• Peptic ulcer disease
• Peritoneal dialysis
• Toxic megacolon
• Volvulus