Peritonitis is inflammation in your peritoneum, the tissue that lines the inside of your abdominal cavity. It’s usually caused by an infection, and sometimes by irritating bodily fluids. Infection in your peritoneum is especially dangerous because it can affect your abdominal organs. It can also transfer to your bloodstream and cause sepsis.


What is peritonitis?

Your peritoneum is a thin membrane that lines the inside of your belly (abdomen) and wraps around the organs inside. Peritonitis is the term for inflammation of the peritoneum. The tissues can become inflamed if they’re exposed to irritating or infected body fluids. This usually happens when something inside leaks or breaks. Infection is the most common cause of peritonitis, and it can be very dangerous.

How does peritonitis affect my body?

Your symptoms may vary depending on the type of peritonitis you have. They usually include abdominal pain and swelling. But it’s the complications that you want to watch out for. Since your peritoneum spreads throughout your abdomen and touches many organs, infections in your peritoneum can affect all of these organs. It can also spread to your bloodstream and become systemic throughout your body.

Is peritonitis an emergency?

Peritonitis can be mild to severe, and it can be localized in one place or diffuse throughout your peritoneum. However, healthcare providers always treat peritonitis as an emergency because it can become severe very quickly, especially if it’s infectious. An infection that spreads to your bloodstream (septicemia) can cause your whole body to go into a kind of shock and shut down vital organs (septic shock).


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Symptoms and Causes

Symptoms of peritonitis include stomach pain and swelling.
The most common symptoms of peritonitis are stomach pain and swelling. If you have an infection, you may also have nausea and fever.

What is the most common cause of peritonitis?

Bacterial infections are the most common cause, especially secondary infections that spread from one of your organs. This can happen if you have a hole in your stomach or intestines that lets bacteria from your gastrointestinal tract enter your peritoneal cavity. A burst appendix from appendicitis is another common cause. Less commonly, bacterial peritonitis can start in your peritoneum itself.

Chemical causes

Inflammation is often caused by an infection, but sometimes it’s just a chemical reaction to different body fluids. For example:

  • Bile can leak from your gallbladder if severe inflammation (cholecystitis) causes a perforation in the tissues. Bile can be irritating with or without bacterial infection.
  • Pancreatic enzymes can leak from your pancreas if severe inflammation (pancreatitis) causes a perforation in the tissues. These can be irritating with or without infection.
  • Stomach acid can leak from your stomach if an ulcer wears a hole all the way through. Gastric acid can irritate even without bacteria.
  • A tumor or cyst that ruptures in your abdomen can cause chemical peritonitis.

Infectious causes

Infectious peritonitis can be either primary or secondary. Primary infectious peritonitis is caused by an infection that originates in your peritoneum itself. Secondary bacterial peritonitis spreads to your peritoneum from somewhere else in your body.

Primary infection is less common than secondary infection. It usually happens in one of two ways:

  • Spontaneous bacterial peritonitis (SBP) develops in people with ascites. This is a condition of excess fluid from leaking veins that accumulates in your peritoneum. Ascites comes from diseases that compromise your immune system, including liver disease, kidney failure, heart failure and cancer. Some of these diseases can also allow small amounts of bacteria to penetrate from your gastrointestinal tract. Retained fluid that isn’t being filtered or cleared as usual, combined with reduced immunity, allows these trace amounts of bacteria to infect the peritoneum.
  • Primary infection can also be introduced to your peritoneal cavity by medical instruments, especially when you use them regularly at home. Dialysis and tube feeding are two ways this can happen. Peritoneal dialysis fills and drains your peritoneal cavity with fluid through a tube (catheter). Long-term tube feeding may pass a catheter directly through your peritoneum to your stomach or small intestine. This breach of organ walls can introduce an infection to the rest of the abdominal cavity.

Secondary infection is the most common cause of peritonitis. It can be caused by:

What are the signs and symptoms of peritonitis?

Typical symptoms include:

If you have an infection, you may also have:

If you have ascites, you may also have:

Can you have peritonitis and not know it?

Yes, it’s possible. Abdominal pain and other symptoms from the original condition that causes your peritonitis can disguise the symptoms of peritonitis itself. Some people have less sensation in their peritoneum if it’s been swollen with ascites for some time. They may not notice the difference if ascites becomes infected. It’s important for healthcare providers to stay alert to the risk of peritonitis.


Diagnosis and Tests

How is peritonitis diagnosed?

Your healthcare provider will begin by asking about your medical history and current conditions. They will physically examine your abdomen and check to see if it is swollen, sensitive to the touch or rigid. If it is, they will follow up with a blood test to check for evidence of inflammation or infection (high white blood cell count). They may also take images of your abdominal organs to look for causes of peritonitis.

One way to confirm and identify the specific infection in your peritoneum is to draw out some of the fluid with a needle (paracentesis) and test it in a lab (peritoneal fluid culture). In cases of ascites, this can also help relieve pressure in your abdomen. In more difficult cases, when your healthcare provider can’t find the cause of your peritonitis, they may need to explore your abdominal cavity in surgery to find and fix the problem.

Management and Treatment

What is the treatment for peritonitis?

Treatment typically begins with IV fluids and broad-spectrum antibiotics to treat or prevent infection. If later tests reveal the exact bacterium or pathogen causing your infection, you may be given a more specific antibiotic for it then. Your healthcare team will work to stabilize your condition before moving on to address the underlying cause. Some causes will require emergency surgery to repair.


Outlook / Prognosis

What are the possible complications of peritonitis?

Peritonitis can lead to:

What is the prognosis for people with peritonitis?

Your outlook depends on the cause and type of peritonitis you have and how quickly it’s treated. Early recognition is important to be able to control peritonitis before it becomes complicated. Treatment is usually effective, but some complications, such as organ damage, may be lasting. Those with weaker immune systems, due to various chronic diseases, are more at risk for complications than others.

A note from Cleveland Clinic

Peritonitis can develop very suddenly, and it’s important to act quickly when it does. Your symptoms and pain levels may or may not seem like an emergency. Abdominal pain can have many different causes, some more serious than others, but if you're in doubt, it doesn’t hurt to check. If you’ve had slowly building symptoms for a while and they suddenly get worse, seek medical attention right away.

Medically Reviewed

Last reviewed on 11/02/2022.

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