Peritonitis is an inflammation or infection of the peritoneum, a membrane that lines the abdominal cavity and organs. In most cases, peritonitis begins when bacteria in the bowel or digestive organs spread through a perforation (hole) into the abdominal cavity.

For example, bacteria may leak through a hole in the gastrointestinal tract due to a ruptured appendix, stomach ulcer or perforated colon. In other instances, biochemicals in the body may irritate the peritoneum and cause peritonitis. For example, pancreatic enzymes may leak into the peritoneum during a bout of pancreatitis.

Peritonitis may be primary (in which the source of contamination is not known) or secondary (in which contamination is caused by a condition, such as appendicitis). A third type of peritonitis can develop in patients undergoing certain types of dialysis (the artificial removal of bodily wastes after kidney failure).

Symptoms associated with peritonitis include fever, vomiting and abdominal pain. Diagnosis of peritonitis typically includes physical examination of the abdomen, imaging studies and blood tests.

Peritonitis is a potentially life-threatening condition that demands immediate medical attention. When bacteria are identified as the source of infection or inflammation, antibiotics will typically be prescribed. In some cases, surgery may be performed to correct the source of the peritonitis, such as removing an inflamed appendix, infected bowel or abscess.

Peritonitis is an inflammation of the abdominal cavity and its lining (peritoneum) that typically also involves infection. The peritoneum is a two-layered membrane that covers the abdominal cavity and lines most of the abdominal organs (e.g., stomach, small and large intestines, appendix, gallbladder).

This membrane helps keep the abdominal organs moist and connects them to blood and lymph vessels. Peritonitis usually develops when an abdominal organ develops a hole (perforation), causing bacteria or digestive enzymes that naturally occur in the gastrointestinal tract to leak into the abdominal cavity. The result is infection and/or irritation.

Peritonitis can also occur if bacteria outside the body infiltrate the peritoneum (e.g., a stomach wound caused by trauma, surgery).

Peritonitis can be primary, in which the source of contamination is unknown, or secondary, in which the source has been identified. A third type of peritonitis can develop in patients undergoing certain types of dialysis (the artificial removal of bodily wastes after kidney failure).

Most cases of peritonitis are secondary. They often involve the rupture of an organ, such as the appendix or gallbladder, resulting in spillage of the organ’s contents into the abdominal cavity. The risk of peritonitis is a primary reason why appendicitis is considered to be a dangerous condition requiring prompt medical attention.

There are two major forms of peritonitis – primary and secondary. Primary peritonitis, in which the source of infection is not known, is often caused by the spread of bacteria in the blood or lymph nodes.

Primary peritonitis is also known as primary bacterial peritonitis (PBP) and spontaneous bacterial peritonitis (SBP). This type of peritonitis is often seen in patients with cirrhosis of the liver, especially those with a history of alcoholism. Primary peritonitis is also associated with other conditions, such as:

• Hepatitis, or inflammation of the liver
  
  
• Metastatic cancers, or cancers that have spread throughout the body
  
  
• Congestive heart failure, in which the heart fails to pump enough blood to meet the body's needs
  
  
• Systemic lupus erythematosus, an inflammatory, autoimmune disease that affects many parts of the body

Primary peritonitis may also occur in patients with no history of underlying disease. Patients who have ascites (fluid buildup in the abdomen) can develop PBP because this fluid provides a good environment for bacteria to grow.

Secondary peritonitis develops when the peritoneum becomes inflamed due to the spillage of gastric contents, which may include digestive enzymes or bacteria. The digestive system contains both naturally occurring bacteria and enzymes that assist in the breakdown of nutrients. These substances are necessary for proper digestion but can cause harm if they escape through a hole (perforation) in one of the abdominal organs.

Because the peritoneum is a conduit for blood and lymph vessels, it is possible for bacteria or toxins to spread to other parts of the body.

A third type of peritonitis may occur in patients undergoing a type of dialysis treatment called continuous ambulatory peritoneal dialysis (CAPD), which is used in patients with kidney failure. During this form of dialysis, fluid  is exchanged through a catheter inserted into the peritoneum to filter waste.

In most cases, peritonitis results from a perforation (hole) in an abdominal organ that causes bacteria or gastric enzymes to leak into the abdominal cavity. However, bacteria in other parts of the body sometimes enter the bloodstream and are carried to the peritoneum.

Sources of peritonitis include:

• Digestive diseases. Various digestive diseases can cause peritonitis. These include appendicitis, diverticulitis, ulcerative colitis, peptic ulcer, cirrhosis, and Crohn's disease.
  

  

• Spontaneous bacterial peritonitis. An infection of an abnormal collection of fluid (ascites) in the peritoneal cavity due to liver or kidney disease.
  
  
• Pelvic inflammatory disease (PID). This results from an infection of the uterus and fallopian tubes that spreads into the abdominal cavity. PID infections are caused by several types of bacteria, including those that cause the sexually transmitted diseases gonorrhea and chlamydia.
  
  
• Surgery. An operation that injures the gallbladder, ureter, bladder or intestine can cause bacteria to spill into the abdominal cavity. Operations to join sections of intestine can also result in leakage that may cause peritonitis. The leakage may be massive or may occur as part of a slow process. Other causes include bacteria introduced after abdominal surgery.
  

  

• Peritoneal dialysis. This treatment for kidney failure is a common source of peritonitis. During this procedure, drains are placed in the abdominal cavity, and infection sometimes enters the cavity through the openings that accommodate these drains.
  
  
• Irritation of abdominal organs. In some cases, infection does not need to be present for peritonitis to occur. Inflammation of the pancreas (acute pancreatitis) is an example of a disorder that does not require infection to produce peritonitis. Talc or starch on a surgeon’s gloves that comes into contact with the peritoneum can cause inflammation without infection.
  

  

• Rupture of tubal (ectopic) pregnancy or ovarian cyst. These events can cause leakage of blood into the peritoneal cavity, resulting in peritonitis.
  
  
• Trauma. Injury to organs in the abdominal cavity due to blunt (e.g, from a car accident) or penetrating (e.g., gun shot) wounds. Inadvertent perforation is a rare complication of upper endoscopy and colonoscopy.
  
  
• Tuberculosis (TB). This infectious disease of the lungs can cause granulomatous peritonitis, an inflammation of the peritoneum characterized by the formation of granulomas (masses of chronically inflamed tissues) and the development of adhesions (growing together of tissues). Although still relatively rare, TB is occurring more frequently in the United States due to HIV infection, immunosuppressive therapy following organ transplantation and immigration.

Specific risk factors associated with primary peritonitis include:

• Cirrhosis
• Kidney damage
• Fluid in the abdomen
• Compromised immune system
• PID

Specific risk factors associated with secondary peritonitis include:

• Appendicitis
• Stomach ulcers
• Torn or twisted intestines
• Severely inflamed gallbladder
• Damage to the pancreas
• Inflammatory bowel disease
• Injury during surgery or endoscopy

Peritonitis may be accompanied by pain that is typically severe and may occur in just one area of the abdomen or throughout the abdomen. In most cases, patients with inflammation caused by peritonitis will experience fever, vomiting and tenderness in the abdomen.

Other symptoms may include:

• Distension or rigidity of the abdomen
• Low urine output
• Loss of appetite
• Thirst
• Inability to pass feces or gas
• Increased breathing and heart rates or shallow breathing
• Low blood pressure
• Chills

Patients whose peritonitis is related to peritoneal dialysis treatment, in which wastes are artificially removed from the body after kidney failure, may notice an unusual color or cloudiness in their used fluid, or redness or pain around the catheter insertion site.  

Peritonitis that is not treated promptly may cause pus-filled areas of infection called abscesses to form inside the abdominal cavity. Infection associated with peritonitis can cause the development of scar tissue that obstructs the intestine. Peritonitis can also halt the process that pushes stool through the intestine (peristalsis) and can cause fluid to leak from the bloodstream into the abdominal cavity. Severe dehydration may cause the body to lose important electrolytes and may be followed by widespread blood clotting and lung, kidney and liver failure.

Once peritonitis occurs, it can be extremely difficult to treat. For this reason, prompt diagnosis is crucial to an overall positive prognosis.

A physician will perform a complete physical examination and compile a thorough medical history. The physician will pay special attention to the abdomen, applying gentle pressure and quickly releasing it to see if the pain worsens, indicating an inflamed peritoneum.

If the physician suspects peritonitis, x-rays may be taken of the patient lying down and standing up. These images can reveal any free gas in the abdominal cavity resulting from a rupture. In some cases, a needle may be used to withdraw fluid from the abdominal cavity. This will allow testing to identify the nature of the infectious organism (whether it is naturally occurring within the body or foreign) and to test how it reacts to different types of antibiotics. Contrast-enhanced  CAT scansCAT scansCAT scans can often help identify the intraabdominal source of a primary bacterial peritonitis  infection.

Other diagnostic tests may include a culture, chemical examination, analysis (paracentesis) or cytologic examination (cell study) of the peritoneal fluid. Blood testing may also be performed to check for an elevated white blood cell count, which may indicate infection.

In addition, researchers have found that monitoring the levels of a chemical hormone in the bloodstream may help to more easily identify peritonitis and other serious abdominal infections that occur after surgery.

In some cases, antibiotics are the only treatment necessary for peritonitis and its associated conditions (e.g., bacteremia, sepsis). This is especially true in cases of primary bacterial peritonitis (PBP). For example, PBP that is treated with antibiotics often improves within 72 hours, with therapy lasting anywhere from a couple of days to two weeks.

Secondary peritonitis may also be treated with antibiotics. However, surgery is usually necessary to treat the source of the inflammation and infection in secondary peritonitis, which can be life-threatening. This may include removing an inflamed appendix, infected bowel or abscess. Antibiotics will also be administered promptly. Patients who undergo surgery may receive intravenous (I.V.) fluids and electrolytes, and a tube may be inserted through the nose and into the stomach or intestine to drain excess fluid or gas.

Continuous ambulatory peritoneal dialysis (CAPD) peritonitis is also treated with antibiotics.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following peritonitis-related questions:

1. I have hepatitis. Am I at increased risk of developing peritonitis?
   
   
2. Are there any activities or foods that increase my risk of peritonitis?
   
   
3. I am on kidney dialysis. Does this increase my risk for peritonitis?
   
   
4. Why do you suspect I may have peritonitis?
   
   
5. What type of peritonitis do I have?
   
   
6. What do you suspect caused my peritonitis?
   
   
7. What are some of the imaging tests that are used to help diagnose peritonitis?
   
   
8. I have been unable to have a bowel movement. Is this a sign of peritonitis?
   
   
9. How are conditions associated with peritonitis, such as bacteremia and sepsis, treated?
   
   
10. After I am treated for peritonitis, is it possible that it may recur?