Peritonitis is inflammation of the peritoneum, the thin layer of tissue that lines the inside of the abdomen (tummy).

It is caused by an infection, which can rapidly spread around the body. Peritonitis requires immediate treatment and is a medical emergency. Signs of peritonitis often develop quickly and include:

  • sudden abdominal pain that becomes more severe
  • feeling sick (nausea)
  • a lack of appetite
  • a high temperature (fever) of 38C (100.4F) or above
  • not passing any urine or passing less than normal

Read more about the symptoms of peritonitis.

When to get medical help

Sudden abdominal pain that gradually gets worse is usually a sign of a potentially serious infection or illness.

If you have this type of pain, contact your GP immediately. If this isn't possible, call NHS Direct Wales on 0845 46 47 or your local out-of-hours service.

Why peritonitis happens

Peritonitis is caused by a bacterial or fungal infection that either develops directly in the peritoneum or spreads from another part of the body.

Most cases of peritonitis are the result of infection or injury to another part of the body, such as:

An infection that develops within the peritoneum isn't common and can be caused by:

Read more about the causes of peritonitis.

How peritonitis is treated

Peritonitis needs to be diagnosed and treated quickly to prevent possibly fatal complications developing, so you will usually be admitted to hospital for tests and treatment.

The underlying infection will be treated with injections of antibiotics or antifungal medication, depending on the cause.

In some cases, surgery may be required to repair the peritoneum or treat the underlying cause of the infection.

Read more about diagnosing peritonitis and treating peritonitis.


Peritonitis can be fatal if the infection spreads through the bloodstream to the major organs (septic shock).

It's estimated about 1 in every 10 people with peritonitis caused by bowel perforation (a hole that develops in the bowel wall) will die, although this can vary considerably depending on what caused the condition, your age, and your general health.

Deaths are less common for peritonitis related to cirrhosis or kidney dialysis, but it's still a serious condition.

Read more about the possible complications of peritonitis.

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Abdominal (tummy) pain is one of the main symptoms of peritonitis.

This usually begins as a sudden ache that develops into a severe pain. Other possible symptoms include:

  • feeling sick (nausea)
  • vomiting
  • lack of appetite
  • chills
  • a high temperature (fever) of 38C (100.4F) or above
  • rapid heartbeat
  • not passing any urine or passing less than normal
  • swelling of the abdomen

If you are being treated with peritoneal dialysis because you have kidney failure, the fluid that is passed into your collection bag will probably be cloudier than usual and may contain white flecks or clumps.

If peritonitis results from cirrhosis, you may not have any pain at all. You may simply feel unwell or develop other complications of liver disease, such as confusion or a build-up of fluid in your abdomen.

When to get medical help

Sudden abdominal pain that gradually gets worse is usually a sign of a potentially serious infection or illness. If you experience this type of pain, contact your GP immediately. If this is not possible, call NHS Direct Wales on 0845 4647 or your local out-of-hours service.

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Peritonitis occurs when the thin layer of tissue lining the tummy (peritoneum) becomes infected with bacteria or fungi.

The infection can either develop directly in the peritoneum or spread from another part of the body.

Infection of other parts of the body

Most often, peritonitis is caused by an infection that spreads to the peritoneum from another part of the body. This is known as secondary peritonitis.

Common causes of secondary peritonitis include:

Both Crohn's disease and diverticulitis can cause the colon to become inflamed. If the inflammation is particularly severe, the colon can split and leak the contents of the bowel into the peritoneum, contaminating it with bacteria.

Direct infection

Peritonitis can occur when the peritoneum becomes directly infected, although this is rare. This is known as primary or spontaneous peritonitis.

In most cases, primary peritonitis is caused by scarring of the liver or peritoneal dialysis.


Scarring of the liver, known as cirrhosis, can occur after liver damage. The most common causes of cirrhosis in the UK are alcohol misuse, a hepatitis C infection, or obesity.

Cirrhosis can lead to a build-up of fluid inside the abdomen (ascites). This fluid is particularly vulnerable to infection, and provides an environment where bacteria or fungi can grow and spread.

This build-up of fluid affects around half of people with cirrhosis, usually many years after cirrhosis was diagnosed. About 20% of people with cirrhosis who develop ascites will be affected by peritonitis.

Peritoneal dialysis

People having peritoneal dialysis for kidney failure are at risk of developing peritonitis. Dialysis is a medical treatment that replicates the main functions of the kidneys and removes waste products from the body.

Peritoneal dialysis uses the peritoneum to replicate the main function of the kidneys, which is to filter waste products out of the blood. A small tube called a catheter is implanted into the peritoneum, which removes waste products.

Although rare, peritonitis can develop if the equipment becomes contaminated by bacteria or fungi.

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Peritonitis can often be diagnosed after a physical examination and tests.

Physical examination

Your GP will ask you about your symptoms and recent medical history, and will carry out a detailed physical examination.

If you have peritonitis, parts of the body such as the abdominal (tummy) wall often become tender to the touch. A physical examination will help rule out other conditions that can cause similar symptoms, such as a hernia.

The risk of complications from peritonitis is high, so you'll be admitted to hospital if your GP suspects you have it.


You may need blood tests and urine tests to check for infection. If you have a build-up of fluid in your abdomen (tummy), a small sample may be removed using a thin needle so it can be checked for infection.

Doctors may also recommend:

  • an X-ray – where radiation is used to produce an image to look for evidence of air leakage from the bowel
  • an ultrasound scan – where sound waves are used to build a picture of the inside of your peritoneum
  • a computerised tomography (CT) scan – a series of X-rays are taken to build up a more detailed three-dimensional picture of your peritoneum

These types of scans can often detect whether there is internal damage inside your abdomen, such as a burst appendix, a ruptured stomach ulcer, or extensive inflammation of the colon.

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If you're diagnosed with peritonitis, you'll be admitted to hospital so you can be carefully monitored.

This is because there is a risk of serious complications of peritonitis, such as blood poisoning.


The initial treatment for peritonitis involves injections of antibiotics or antifungal medicines. This usually lasts 10 to 14 days.

If your peritonitis was caused by peritoneal dialysis, antibiotics may be injected directly into the peritoneum. Research has shown this is more effective than injecting antibiotics into a vein.

You'll also need to use an alternative method of dialysis until the peritonitis has been successfully treated. You may also be given painkilling medication if you are in pain.

Nutritional support

Many people with peritonitis have problems digesting food, so a feeding tube may be needed.

The feeding tube is either passed into your stomach through your nose (nasogastric tube) or surgically placed into your stomach through your stomach.

If these are unsuitable, nutrition may be given directly into one of your veins (parenteral nutrition).


If part of the tissue of the peritoneum has been seriously damaged by infection, it may need to be surgically removed.

Some people develop abscesses (pus-filled swellings) in their peritoneum that need to be drained with a needle. This is carried out using an ultrasound scanner to guide the needle to the abscess. Local anaesthetic is usually used so you don't feel any pain.

Read more about treating abscesses.

The cause of peritonitis may also need to be surgically treated. For example, if a burst appendix caused your peritonitis, your appendix will need to be removed.

Read more about treating appendicitis.

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Serious complications of peritonitis can occur if the infection spreads to other parts of the body.

You'll usually be admitted to hospital if you are diagnosed with peritonitis, so any problems can be identified and treated as quickly as possible.


Sepsis can occur if the infection spreads through the blood (septicaemia) and then to other organs.

If sepsis is not treated, it can become severe sepsis. This occurs when one or more organs are damaged by the infection, or when there is a significant loss of blood supply to tissues and organs.

The symptoms of sepsis usually develop quickly and include:

  • a fever or high temperature over 38C (100.4F)
  • chills
  • a fast heartbeat
  • fast breathing

Treatment for sepsis involves fluids being given directly into a vein (intravenous fluid therapy) and antibiotic injections.

If sepsis is not treated promptly, it can develop into septic shock.

Septic shock

Septic shock is a type of sepsis that causes a massive drop in blood pressure. This leads to symptoms of shock, such as cold skin and an increased heartbeat.

Sepsis can interfere with many of the body's vital processes, including blood pressure, breathing and organ function, and can result in death.

Treatment usually requires admission to an intensive care unit (ICU), where the functions of the body's organs are supported while the infection is treated.

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 23/04/2015 11:10:46