An Overview of Peritonitis

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Peritonitis is when the peritoneum—the thin layer of tissue that covers the inner wall of the abdomen and abdominal organs—becomes irritated or inflamed. It’s usually due to a bacterial or fungal infection, and the primary symptom is severe stomach pain.

In some cases, the peritonitis could be the result of something else going on in the abdominal area, such as a burst appendix. Because the condition can be deadly if it’s left untreated, it’s important to diagnose and treat those with peritonitis as soon as possible.

Common symptoms of peritonitis
Verywell / JR Bee


Symptoms of peritonitis can be serious and excruciating. Pain can be so intense that individuals resort to curling up in a ball as they try to stay as still as possible.

The most common symptom is sudden, extreme abdominal pain that gets worse when you touch the affected area or move around. The abdomen might also look or feel bloated.

Depending on the source and intensity of the inflammation, other signs and symptoms can be present, too, including:

  • Fever
  • Chills
  • Constipation or inability to pass gas
  • Fatigue
  • Diarrhea
  • Nausea or vomiting
  • Racing heart rate
  • Abnormal breathing

Some patients (especially those with cirrhosis) might not show any symptoms at all, which can make it difficult to detect and treat quickly.

If you show any signs of peritonitis, go to the emergency room or call an ambulance right away. Sudden abdominal pain may have other causes, but medical attention is required to determine the issue and start treatment. In serious cases, peritonitis can cause life-threatening issues like shock, sepsis, hypothermia, internal bleeding, or an obstruction in the intestines. The severity of these symptoms often depends on what caused the inflammation in the first place.


Peritonitis occurs when body fluids like blood or pus pool in the abdominal cavity. Why this happens, however, can vary. The two primary causes of peritonitis are spontaneous bacterial peritonitis (also called primary peritonitis) and secondary peritonitis.

Secondary Peritonitis

Secondary peritonitis is the more common of the two causes and is typically the result of a rupture or injury in an organ along the digestive tract. When this happens, the fluid inside the organ starts to leak out, contaminating the normally sterile abdominal cavity with foreign substances like bacteria, gastric acid, or even partially digested food.

Common causes include:

  • An organ gets perforated (such as via a burst appendix or diverticula, stomach ulcer, or knife wound) and bacteria makes its way into the cavity through the opening.
  • Sudden swelling of the pancreas causes bile or other chemicals to leak out into the abdominal area.
  • Feeding tubes, catheters, or other items placed into the abdomen provide an opportunity for bacteria to enter the area.

On rare occasions, sepsis (or an infection in the bloodstream) can carry bacteria into the abdomen, which can lead to inflammation.

Spontaneous Bacterial Peritonitis

Spontaneous bacterial peritonitis (SBP), or primary peritonitis, is when body fluid builds up in the abdominal cavity (a condition called ascites) and results in inflammation. Unlike with secondary peritonitis, where the peritoneal inflammation is often due to an identifiable infection, SBP is an infection of the ascites and enclosing peritoneum without a clear source.

Not everyone with ascites will get peritonitis—it happens in as many as 18% of people with ascites—but those who have had SBP before are more likely to get it again.

According to one estimate, the majority (50-70%) of people who survive an episode of primary peritonitis will go on to develop another one that same year.

People with ascites (whether from liver disease, heart failure, cancer, or other causes) have the highest risk of developing SBP. Those with cirrhosis are particularly vulnerable to severe cases of primary peritonitis. Anywhere from 40-70% of adults with cirrhosis who develop SBP die from it.


Because peritonitis can be life-threatening very quickly, it’s important to find out as soon as possible if you have it. Healthcare providers use a combination of methods to diagnose peritonitis, including a physical exam, lab work, or other additional tests.

Physical Examination

Your healthcare provider will ask you to point to where the pain is, report when it appeared, and ask how severe it is. The practitioner will also listen to and feel your abdomen to look for signs of peritonitis, including pain to touch, and a firm, “board-like” consistency. Examination can be impossible for some patients with severe pain.

Lab Tests

Depending on the results of the physical exam, your healthcare provider might also recommend getting lab tests, such as a white blood cell count, urinalysis, or cultures, to look for signs of infection. A common diagnostic test used to detect peritonitis involves taking a sample of the fluid in your abdomen to test it for infection.

Additional Testing

If your healthcare provider thinks you might have peritonitis, they might call for additional tests or imaging to see the extent of the inflammation or identify the source of the infection. These tests could include CT scans or ultrasounds—these tests can be used to guide needles or drains if fluid pockets need to be sampled or drained.

In severe cases, your practitioner might recommend surgery to find the source of the infection so it can be removed quickly.


Treatment for peritonitis depends entirely on the cause of the inflammation and/or infection and the severity of the symptoms. The most common method is using antibiotics (typically through an IV) to treat the infection causing the pain and inflammation.

For secondary peritonitis, surgery is sometimes necessary to eliminate the source of infection. This is especially true if the peritonitis is the result of a swollen or burst appendix, sores caused by stomach or intestinal ulcers, or inflamed or perforated diverticula (tiny pouches in the colon).

Note, for most cases of primary peritonitis, SBP antibiotics are the main treatment and surgery isn't usually needed.

A Word From Verywell

Peritonitis can be fatal if it isn’t treated as soon as possible. If you’re worried you might be experiencing some of the symptoms associated with the condition, talk to a healthcare provider or go to the hospital right away.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Robyn Correll, MPH
Robyn Correll, MPH holds a master of public health degree and has over a decade of experience working in the prevention of infectious diseases.