In most cases, peritonitis results from a perforation (hole) in an abdominal organ that causes bacteria or gastric enzymes to leak into the abdominal cavity. However, bacteria in other parts of the body sometimes enter the bloodstream and are carried to the peritoneum.

Sources of peritonitis include:

• Digestive diseases. Various digestive diseases can cause peritonitis. These include appendicitis, diverticulitis, ulcerative colitis, peptic ulcer, cirrhosis, and Crohn's disease.
  

  

• Spontaneous bacterial peritonitis. An infection of an abnormal collection of fluid (ascites) in the peritoneal cavity due to liver or kidney disease.
  
  
• Pelvic inflammatory disease (PID). This results from an infection of the uterus and fallopian tubes that spreads into the abdominal cavity. PID infections are caused by several types of bacteria, including those that cause the sexually transmitted diseases gonorrhea and chlamydia.
  
  
• Surgery. An operation that injures the gallbladder, ureter, bladder or intestine can cause bacteria to spill into the abdominal cavity. Operations to join sections of intestine can also result in leakage that may cause peritonitis. The leakage may be massive or may occur as part of a slow process. Other causes include bacteria introduced after abdominal surgery.
  

  

• Peritoneal dialysis. This treatment for kidney failure is a common source of peritonitis. During this procedure, drains are placed in the abdominal cavity, and infection sometimes enters the cavity through the openings that accommodate these drains.
  
  
• Irritation of abdominal organs. In some cases, infection does not need to be present for peritonitis to occur. Inflammation of the pancreas (acute pancreatitis) is an example of a disorder that does not require infection to produce peritonitis. Talc or starch on a surgeon’s gloves that comes into contact with the peritoneum can cause inflammation without infection.
  

  

• Rupture of tubal (ectopic) pregnancy or ovarian cyst. These events can cause leakage of blood into the peritoneal cavity, resulting in peritonitis.
  
  
• Trauma. Injury to organs in the abdominal cavity due to blunt (e.g, from a car accident) or penetrating (e.g., gun shot) wounds. Inadvertent perforation is a rare complication of upper endoscopy and colonoscopy.
  
  
• Tuberculosis (TB). This infectious disease of the lungs can cause granulomatous peritonitis, an inflammation of the peritoneum characterized by the formation of granulomas (masses of chronically inflamed tissues) and the development of adhesions (growing together of tissues). Although still relatively rare, TB is occurring more frequently in the United States due to HIV infection, immunosuppressive therapy following organ transplantation and immigration.

Specific risk factors associated with primary peritonitis include:

• Cirrhosis
• Kidney damage
• Fluid in the abdomen
• Compromised immune system
• PID

Specific risk factors associated with secondary peritonitis include:

• Appendicitis
• Stomach ulcers
• Torn or twisted intestines
• Severely inflamed gallbladder
• Damage to the pancreas
• Inflammatory bowel disease
• Injury during surgery or endoscopy