Peritonitis

Peritonitis is inflammation of the peritoneum due to a bacterial or fungal infection. The most common symptom of peritonitis is severe abdominal pain.

The peritoneum

The peritoneum is a thin membrane (covering) that lines the inside of the abdomen and surrounds and supports the abdominal organs, such as the stomach and liver.

The tissue of the peritoneum is usually sterile (germ-free) so unlike other parts of the body, such as the skin, it does not have an inbuilt defence mechanism for fighting off infection. In peritonitis, an infection can rapidly spread into the blood (sepsis) and then to other organs, carrying the risk of multiple organ failure and, if left untreated, death.

Types of peritonitis

There are two main types of peritonitis:

• primary spontaneous peritonitis, where an infection develops in the peritoneum, and
• secondary peritonitis, where an infection or injury in another part of the body leads to bacteria or fungi infecting the peritoneum.

How common is peritonitis?

Peritonitis is generally rare but can be a common complication in people with pre-existing risk factors. Cirrhosis (scarring of the liver, usually due to alcohol abuse) is one of the leading risk factors for peritonitis as it can cause a build-up of fluid (ascites) inside the abdomen. Sometimes, the fluid can become infected.

It is estimated that between 10% and 30% of people with cirrhosis and ascites will experience at least one episode of peritonitis. See the Causes section, above, for more information about risk factors for peritonitis.

Outlook

Peritonitis is a serious condition that needs to be diagnosed and treated quickly to prevent possibly fatal complications developing, such as multiple organ failure. However, due to the often aggressive nature of peritonitis, deaths can occur despite the best efforts of medical staff.

Approximately 10% of people with primary spontaneous peritonitis will die as a result of complications. The outlook for secondary peritonitis is slightly better, with a mortality rate of under 5%.

Almost all cases of peritonitis will require admission to hospital. The condition is usually treated with a combination of antibiotics (or antifungal medication in the case of fungal infections) and surgery to remove infected tissue.