Inflammation of the peritoneum (the tissue layer of cells lining the inner wall of the abdomen and pelvis).

Peritonitis can result from infection; such as, bacteria or parasites, injury and bleeding, or diseases; such as, systemic lupus erythematosus.

Lupus is a condition of chronic inflammation caused by an autoimmune disease. Autoimmune diseases are illnesses which occur when the body's tissues are attacked by its own immune system.