peritonitis (pĕrˌĭtənĪˈtĭs) [key], acute or chronic inflammation of the peritoneum, the membrane that lines the abdominal cavity and surrounds the internal organs. It is caused by invasion of bacterial agents or irritant foreign matter during rupture of an internal organ, by spreading infection from the female genital tract, by penetrating injuries of the abdominal wall, by dissemination of infections through the blood and lymphatic channels, or by accidental pollution during surgery. Typically, peritonitis is a serious complication of another abdominal disorder, such as appendicitis, ulcers, colitis, or rupture of the gall bladder. Severe abdominal pain, vomiting, prostration, and high fever are predominant symptoms. Treatment includes antibiotic therapy and the identification and elimination of the cause of the infection.