peritonitis
Meaning of peritonitis: Contamination of a normally sterile space, across a membrane broad enough that bacteria crossing it pass quickly into the bloodstream.
Definition of peritonitis
Peritonitis is inflammation of the peritoneum, the thin membrane lining the inner wall of the abdomen and wrapping most of the organs inside it. It usually follows infection reaching a space that is normally sterile, most often through a hole somewhere in the digestive tract. The result is widespread abdominal pain and tenderness, often with a rigid, guarded abdomen.
How does infection get into the peritoneal space?
| Route | Typical setting |
|---|---|
| A hole in a hollow organ | Ruptured appendix, perforated ulcer, diverticulitis breaking through the bowel wall, penetrating injury, a surgical join that leaks |
| A catheter through the abdominal wall | Peritoneal dialysis, where organisms travel along or through the tubing |
| No hole at all | Advanced liver disease with fluid in the abdomen, which bacteria seed from the bloodstream or bowel wall |
That last form is called spontaneous bacterial peritonitis, and it matters because nothing has perforated. It is found by sampling the fluid rather than by looking for a leak, and it usually involves a single organism, whereas a perforation delivers the mixed population living inside the bowel.
Why does it turn serious so quickly?
The peritoneal cavity is lined by a membrane with an enormous surface area that absorbs readily, which is what makes it usable for dialysis in the first place. The same property works against the body during infection: bacteria and their toxins pass into the bloodstream, and the whole body response that follows brings fever, a racing heart, falling blood pressure and failing organs. Meanwhile fluid pours out of the circulation into the inflamed cavity, and the bowel stops propelling its contents. Untreated, this sequence progresses to shock, which is why peritonitis is handled as a surgical emergency and why treatment attends to the source of contamination as well as the infection itself.
How is it recognized?
The pain is constant and worsened by anything that moves the membrane, so coughing, walking, or the jolt of a bed being knocked makes it sharply worse. The abdominal muscles tighten over the inflamed area and stay tight, a finding described as guarding or, when the whole abdomen is board-like, rigidity. Bowel sounds fade. Gas escaping from a perforated organ collects under the diaphragm and shows on an upright chest image. In someone receiving peritoneal dialysis the drained fluid turns cloudy and its white cell count climbs, often before pain is prominent.
Used in a sentence
The patient's rigid, tender abdomen and fever raised concern for peritonitis following the suspected perforation.
Good to know
Peritonitis from a perforated organ, peritonitis complicating peritoneal dialysis, and spontaneous bacterial peritonitis in advanced liver disease differ in how bacteria arrive and in which organisms are usually found.
Word origin
Where “peritonitis” comes from
Formed from Greek peri, meaning around, and teinein, meaning to stretch, describing a membrane stretched around the abdominal organs, combined with -itis, meaning inflammation.