Peritonitis is defined as inflammation of the peritoneum (the serous membrane which lines part of the abdominal cavity and some of the viscera it contains). It may be localised or generalised, generally has an acute course, and may depend on either infection (often due to rupture of a hollow organ as may occur in abdominal trauma) or on a non-infectious process. Peritonitis generally represents a surgical emergency.
Mechanisms and manifestations
Abdominal pain and tenderness
The main manifestations of peritonitis are acute abdominal pain
, abdominal tenderness
, and abdominal guarding
, which are exacerbated by moving the peritoneum, e.g. coughing, flexing the hips, or eliciting the Blumberg sign
(a.k.a. rebound tenderness
, 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). The presence of these signs in a patient is sometimes referred to as peritonism. The localization of these manifestations depends on whether peritonitis is localised (e.g. appendicitis
before perforation), or generalised to the whole abdomen
. In either case pain typically starts as a generalised abdominal pain (with involvement of poorly localising innervation of the visceral peritoneal layer
), and may become localised later (with the involvement of the somatically innervated parietal peritoneal layer). Peritonitis is an example of an acute abdomen
Diagnosis and investigations
of peritonitis is based primarily on clinical grounds, that is on the clinical manifestations described above; if they support a strong suspicion of peritonitis, surgery
is performed without further delay from other investigations. Leukocytosis
may be present, but they are not specific findings. Plain abdominal X-rays
may reveal dilated, oedematous intestines, although it is mainly useful to look for pneumoperitoneum
(free air in the peritoneal cavity), which may also be visible on chest X-rays
. If reasonable doubt still persists, an exploratory peritoneal lavage
may be performed (e.g. in cases of trauma
, in order to look for white blood cells
, red blood cells
, or bacteria
- Perforation of a hollow viscus is the most common cause of peritonitis. Examples include perforation of the distal oesophagus (Boerhaave syndrome), of the stomach (peptic ulcer, gastric carcinoma), of the duodenum (peptic ulcer), of the remaining intestine (e.g. appendicitis, diverticulitis, Meckel diverticulum, inflammatory bowel disease (IBD), intestinal infarction, intestinal strangulation, colorectal carcinoma, meconium peritonitis), or of the gallbladder (cholecystitis). Other possible reasons for perforation include abdominal trauma, ingestion of a sharp foreign body (such as a fish bone, toothpick or glass shard), perforation by an endoscope or catheter, and anastomotic leakage. The latter occurrence is particularly difficult to diagnose early, as abdominal pain and ileus paralyticus are considered normal in patients who just underwent abdominal surgery. In most cases of perforation of a hollow viscus, mixed bacteria are isolated; the most common agents include Gram-negative bacilli (e.g. Escherichia coli) and anaerobic bacteria (e.g. Bacteroides fragilis). Fecal peritonitis results from the presence of faeces in the peritoneal cavity. It can result from abdominal trauma and occurs if the large bowel is perforated during surgery.
- Disruption of the peritoneum, even in the absence of perforation of a hollow viscus, may also cause infection simply by letting micro-organisms into the peritoneal cavity. Examples include trauma, surgical wound, continuous ambulatory peritoneal dialysis, intra-peritoneal chemotherapy. Again, in most cases mixed bacteria are isolated; the most common agents include cutaneous species such as Staphylococcus aureus, and coagulase-negative staphylococci, but many others are possible, including fungi such as Candida.
- Spontaneous bacterial peritonitis (SBP) is a peculiar form of peritonitis occurring in the absence of an obvious source of contamination. It occurs either in children, or in patients with ascites. See the article on spontaneous bacterial peritonitis for more information.
- Systemic infections (such as tuberculosis) may rarely have a peritoneal localisation.
- Leakage of sterile body fluids into the peritoneum, such as blood (e.g. endometriosis, blunt abdominal trauma), gastric juice (e.g. peptic ulcer, gastric carcinoma), bile (e.g. liver biopsy), urine (pelvic trauma), menstruum (e.g. salpingitis), pancreatic juice (pancreatitis), or even the contents of a ruptured dermoid cyst. It is important to note that, while these body fluids are sterile at first, they frequently become infected once they leak out of their organ, leading to infectious peritonitis within 24-48h.
- Sterile abdominal surgery normally causes localised or minimal generalised peritonitis, which may leave behind a foreign body reaction and/or fibrotic adhesions. Obviously, peritonitis may also be caused by the rare, unfortunate case of a sterile foreign body inadvertently left in the abdomen after surgery (e.g. gauze, sponge).
- Much rarer non-infectious causes may include familial Mediterranean fever, porphyria, and systemic lupus erythematosus.
Depending on the severity of the patient's state, the management of peritonitis may include:
If properly treated, typical cases of surgically correctable peritonitis (e.g. perforated peptic ulcer
, and diverticulitis
) have a mortality rate
of about <10% in otherwise healthy patients
, which rises to about 40% in the elderly
, and/or in those with significant underlying illness
, as well as in cases that present late (after 48h). If untreated, generalised peritonitis is almost always fatal.
normally 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 dehydrated patients, 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
features infiltration by neutrophils
with fibrino-purulent exudation.