Peritonitis is a condition of the peritoneum that typically occurs following a bacterial infection.

The perioneum is the moist tissue around the inside of the stomach wall.

Peritonitis is a serious and urgent condition that requires immediate treatment. Symptoms include sudden, severe abdominal pain.

A rupture, also known as a perforation, often causes infection. One example is the rupture of the appendix during a case of appendicitis. Pus from the infection can move from the gut into the peritoneum.

Fast facts on peritonitis

  • Peritonitis is an infection of the stomach lining.
  • It can cause swelling and severe stomach pain. Peritonitis is considered a medical emergency.
  • The condition can be diagnosed using CT scans, ultrasound scans, and blood tests.
  • Peritonitis can be caused by injury or infection.
  • It is treated with IV antibiotics or surgery, depending on the cause.
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The main symptom of peritonitis is a swollen and painful stomach.

The symptoms of peritonitis are serious. They need urgent medical attention in a nearby emergency room or an ambulance callout.

People who develop peritonitis while already in hospital need urgent attention.

The main symptom is sudden, severe stomach pain that gets worse.

Some effects of peritonitis are related to serious effects in the body such as dehydration and shock. Other symptoms include:

  • fever
  • nausea and vomiting
  • diarrhea
  • loss of appetite
  • fast heart rate
  • inability to pass stool or gas, and difficulties passing urine

It is important to get medical help for these symptoms whether they relate to peritonitis or not.

Doctors will want to rule out peritonitis or treat other potentially life-threatening conditions.

Swollen abdomen

A swollen abdomen is also a symptom of peritonitis. When a rupture causes peritonitis, fluid fills the abdominal cavity and the bowel, resulting in loss of fluid from the rest of the body. This causes the worst dehydration effects of peritonitis.

When liver disease is the cause of peritonitis, a swollen abdomen can occur for a different reason. This usually occurs without the perforation seen in other types of peritonitis. This is known spontaneous bacterial peritonitis.

This form of peritonitis has different symptoms. Discomfort is the main symptom of spontaneous bacterial peritonitis due to the pressure of the increased fluid. For people with liver disease whose swollen abdomens become infected, the pain is mild to moderate, not severe.


Without prompt treatment, peritonitis can lead to more dangerous conditions such as sepsis and septic shock. As a result, the condition can quickly become life-threatening.

The abdominal cavity contains the main parts of the gut, such as the stomach and intestines. It also contains other organs such as the liver and kidneys.

The peritoneum lines the abdominal wall but also forms folds that go inward. By folding in, the peritoneum weaves between abdominal organs, providing a membrane that protects and stabilizes the organs in the abdomen.

The folds of the peritoneum also contain blood and nerve supplies. These vessels can be seen running through the membrane that secures the intestines.

Infections cause most cases of peritonitis. In rare cases, these are infections of the peritoneum itself, but infections from elsewhere in the body are a more common cause.

A rupture in the gut is often a source of infection. Ruptures can come from a burst appendix or a hole created by a severe stomach ulcer.

People on a type of kidney dialysis that involves exchanging peritoneal fluids can also become infected.

Other possible causes include:

  • inflammation of the pancreas
  • inflammation of the gut by conditions such as Crohn’s disease
  • diverticulitis, or inflammation of pouches in the large bowel wall
  • injuries that cause abdominal trauma, such as knife or gun wounds

Peritonitis can happen to people who have excess fluid in their abdomen because of long-standing disease, especially liver disease. This is one of the less common causes.

While uncommon, the peritoneum can also be affected by cancer.

People with suspected peritonitis should visit a doctor for diagnosis as soon as possible.

A doctor will question the individual about their symptoms to help them narrow down the exact type, timing, and location of symptoms.

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An ultrasound scan may be carried out to identify any physical injuries to the peritoneum.

A person with peritonitis may not notice any symptoms but a doctor can detect the condition before symptoms become noticeable.

During peritoneal dialysis for kidney disease, for example, a patient will be at risk of infection through the abdominal wall. Doctors will monitor the appearance and may diagnose and treat peritonitis straight away if this fluid is cloudy.

For any case of suspected peritonitis, doctors check the signs by carrying out a physical examination of the abdomen.

Further investigations are made to check for infection. These tests might include:

  • blood samples to confirm immune reaction
  • blood samples to test for wider bacterial complications
  • X-ray or ultrasound imaging to help to locate ruptures in the gut
  • CT imaging that can provide a more detailed computer picture


Another diagnostic procedure is paracentesis. This involves taking fluid from the abdomen to directly check for infection. A thin needle is inserted through the abdominal wall under local anesthetic.

The fluid is then tested for signs of inflammation and infection.

Excess fluid in the abdomen can fill the abdominal cavity between the organs. Doctors call this condition ascites, and the fluid is known as ascitic fluid.

The test includes sending off the fluid sample to analyze white blood cell counts and chemicals. The lab can also look for bacteria and other microbes under the microscope, or by using stains and cultures.

Not all cases of peritonitis require paracentesis.

Having fluid in the abdomen may be the reason for the hospital visit in the first place. This extra fluid is more common in people who have liver disease.

According to a paper by the American College of Gastroenterologists, spontaneous bacterial peritonitis is found in some 20 percent of people admitted to hospital with ascites because of liver cirrhosis.

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IV antibiotic treatment can help with peritonitis.

Peritonitis is considered an emergency and treatment is normally carried out in-hospital.

Treatment options will include:

  • Antibiotic medications: These can be applied directly to the blood using intravenous (IV) injection. The doctor will start by using general purpose antibiotics before waiting for the tests to identify the bacteria. If the more general antibiotic medications do not have the desired effect, a doctor may administer more specific drugs later.
  • Surgery: Doctors will consider surgery in cases where the cause is, for example, a hole in the gut. An operation may also be needed to remove damaged peritoneal tissue.
  • Wider support therapies: These therapies can range from intensive life support to dietary assistance.


Peritonitis is not always preventable, and it can happen without warning. However, some cases can be preventable.

Good clinical hygiene is vital. This is especially true for people with kidney disease who have the peritoneal form of dialysis. Infections can be introduced into the abdomen this way, so hygiene preparations before dialysis can be central to the prevention of peritonitis.

Rapid treatment can help prevent some potential cases of peritonitis. If a gut perforation or rupture is the cause, quick action could prevent the condition from developing.

People should call for medical attention immediately after the onset of severe stomach pain.