Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part or the entire abdomen may be tender. Complications may include shock and acute respiratory distress syndrome. Causes include perforation of the intestinal tract, pancreatitis, pelvic inflammatory disease, stomach ulcer, cirrhosis, a ruptured appendix or even a perforated gallbladder. Risk factors include ascites (the abnormal build-up of fluid in the abdomen) and peritoneal dialysis. Diagnosis is generally based on examination, blood tests, and medical imaging. Treatment often includes antibiotics, intravenous fluids, pain medication, and surgery. Other measures may include a nasogastric tube or blood transfusion. Without treatment death may occur within a few days. About 20% of people with cirrhosis who are hospitalized have peritonitis.

Signs and symptoms

Abdominal pain

The main manifestations of peritonitis are acute abdominal pain, abdominal tenderness, abdominal guarding, rigidity, which are exacerbated by moving the peritoneum, e.g., coughing (forced cough may be used as a test), flexing one's hips, or eliciting the Blumberg's sign (meaning that pressing a hand on the abdomen elicits less pain than releasing the hand abruptly, which will aggravate the pain, as the peritoneum snaps back into place). Rigidity is highly specific for diagnosing peritonitis (specificity: 76–100%). The presence of these signs in a person is sometimes referred to as peritonism. The localization of these manifestations depends on whether peritonitis is localized (e.g., appendicitis or diverticulitis before perforation), or generalized to the whole abdomen. In either case, pain typically starts as a generalized abdominal pain (with involvement of poorly localizing visceral innervation of the visceral peritoneal layer), and may become localized later (with involvement of the somatic innervation of the parietal peritoneal layer). Peritonitis is an example of an acute abdomen.

Other symptoms

Complications

Causes

Infection

Non-infection

Risk factors

Diagnosis

A diagnosis of peritonitis is based primarily on the clinical manifestations described above. Rigidity (involuntary contraction of the abdominal muscles) is the most specific exam finding for diagnosing peritonitis. If focal peritonitis is detected, further work-up should be done. If diffuse peritonitis is detected, then urgent surgical consultation should be obtained, and may warrant surgery without further investigations. Leukocytosis, hypokalemia, hypernatremia, and acidosis may be present, but they are not specific findings. Abdominal X-rays may reveal dilated, edematous intestines, although such X-rays are mainly useful to look for pneumoperitoneum, an indicator of gastrointestinal perforation. The role of whole-abdomen ultrasound examination is under study and is likely to expand in the future. Computed tomography (CT or CAT scanning) may be useful in differentiating causes of abdominal pain. If reasonable doubt still persists, an exploratory peritoneal lavage or laparoscopy may be performed. In people with ascites, a diagnosis of peritonitis is made via paracentesis (abdominal tap): More than 250 polymorphonuclear cells per μL is considered diagnostic. In addition, Gram stain is almost always negative, whereas culture of the peritoneal fluid can determine the microorganism responsible and determine their sensitivity to antimicrobial agents.

Pathology

In normal conditions, the peritoneum appears greyish and glistening; it becomes dull 2–4 hours after the onset of peritonitis, initially with scarce serous or slightly turbid fluid. Later on, the exudate becomes creamy and evidently suppurative; in people who are dehydrated, it also becomes very inspissated. The quantity of accumulated exudate varies widely. It may be spread to the whole peritoneum, or be walled off by the omentum and viscera. Inflammation features infiltration by neutrophils with fibrino-purulent exudation.

Treatment

Depending on the severity of the person's state, the management of peritonitis may include:

Prognosis

If properly treated, typical cases of surgically correctable peritonitis (e.g., perforated peptic ulcer, appendicitis, and diverticulitis) have a mortality rate of about <10% in otherwise healthy people. The mortality rate rises to 35% in peritonitis patients who develop sepsis, and patients who have underlying renal insufficiency and complications have a higher mortality rate.

Etymology

The term "peritonitis" comes from Greek περιτόναιον peritonaion "peritoneum, abdominal membrane" and -itis "inflammation".