Peritonitis

The organs inside the abdominal cavity are each surrounded by a thin membrane called the visceral peritoneum. Similarly, the abdominal wall itself is surrounded by a thin membrane called the parietal peritoneum. These membranes are normally very close together and separated by a small amount of fluid, which is normally present for lubrication as the intestines move.

Sometimes an abnormal amount of fluid collects in the potential space in the abdomen. Irritation of these membranes leads to inflammation and is very painful. Whenever one of the hollow organs perforates (such as a ruptured appendix or a perforated ulcer -- just like the hose breaking inside the bag), the contents of the bowels (food) spill into the peritoneal space and cause severe pain. Such patients are said to have peritonitis (inflammation of the peritoneum) and are almost always in need of emergency surgery. When peritonitis occurs, the bowels stop moving completely and any movement or stretching of the peritoneal membranes causes extreme pain. For this reason, the abdominal muscles contract involuntarily, and the abdomen becomes rigid. There are several classic and easy signs of peritonitis which doctors routinely check for in very ill patients.

1. Absent bowel sounds: the bowels have stopped moving altogether.
2. Guarding: the patient has so much pain from the irritation of the peritoneal membranes that their abdominal muscles are contracted, and it is difficult to feel any other abdominal structures on examination.
3. Rebound tenderness: any movement or stretching of the membranes causes severe pain. For instance, if the doctor presses firmly but gently and then rapidly withdraws his or her hand, this causes the membrane to suddenly stretch back into its original position -- and produces pain in the patient's abdomen. Similarly, even jiggling the bed would cause pain for the same reason