Peritonitis

What the peritoneum does

The peritoneum is a two-layered membrane. One layer lines the abdominal wall, the other wraps the bowel, stomach, liver and other organs. A small amount of fluid between the layers lets the organs slide as you move and breathe. The peritoneum has a rich nerve supply, so when it is inflamed, the pain is sharp and well localized, and any movement hurts.

When infection or irritating material such as stomach acid, bile, blood or stool reaches the peritoneum, it becomes inflamed. Fluid shifts into the abdomen, the bowel stops moving (ileus) and bacteria and toxins can enter the bloodstream, leading to sepsis.

Signs and symptoms of peritonitis

Symptoms

• Abdominal pain: severe, constant and getting worse. It may start in one area and then spread over the whole belly.
• Pain with any movement: people often lie very still with knees bent. Coughing, walking or bumps in the road make it worse.
• Swollen, bloated belly
• Fever and chills
• Nausea, vomiting and loss of appetite
• Not passing gas or stool
• Passing little urine, a sign of dehydration
• Thirst, weakness and confusion as illness progresses

Signs a doctor looks for

• Guarding: involuntary tensing of the belly muscles when pressed.
• Rigidity: a board-like belly, classic with a perforated ulcer.
• Rebound tenderness: pain that is worse when pressure is released.
• Absent bowel sounds
• Fast pulse, low blood pressure and fast breathing, signs that sepsis may be developing.

Older adults, people taking steroids and people with weakened immune systems may have surprisingly mild pain and tenderness even with serious peritonitis.

Types of peritonitis

What causes peritonitis

Secondary peritonitis

• Appendicitis that bursts, the most common cause in younger people
• Peptic ulcer perforation, causing sudden, severe upper belly pain
• Diverticulitis with perforation, common in older adults
• Bowel perforation from obstruction, cancer, inflammatory bowel disease or ischemia
• Gallbladder rupture or bile leaks
• Severe pancreatitis
• Trauma: stab and gunshot wounds, or blunt injury to the bowel
• After surgery or procedures: a leak from a bowel join (anastomotic leak), or a perforation during colonoscopy
• Pelvic infections: pelvic inflammatory disease or infection after childbirth

Spontaneous bacterial peritonitis

People with cirrhosis often collect fluid in the abdomen (ascites). Bacteria from the gut can infect this fluid. Symptoms are often vague: mild belly pain, fever, worsening confusion or kidney function. Some have no pain at all, which is why doctors test the fluid whenever someone with ascites becomes unwell.

Risk factors

• cirrhosis with ascites
• peritoneal dialysis
• previous abdominal surgery
• inflammatory bowel disease, diverticular disease or peptic ulcers
• weakened immunity
• NSAID use (raises the risk of ulcers)

How peritonitis is diagnosed

• Examination: pain, guarding, rigidity and vital signs. A doctor may diagnose it from examination alone and go straight to surgery if the patient is very unwell.
• Blood tests: white blood cells, CRP, lactate, kidney and liver function, and blood cultures.
• CT scan of the abdomen: shows free air from a perforation, abscesses, an inflamed appendix or diverticulitis.
• Upright chest X-ray: can show air under the diaphragm from a perforation.
• Paracentesis: a needle sample of ascites fluid. A high count of neutrophils (a type of white blood cell) confirms SBP.
• Dialysis fluid testing: cell count and culture in peritoneal dialysis patients.

Treatment

Emergency treatment

• IV fluids to correct dehydration and support blood pressure.
• Broad-spectrum IV antibiotics started quickly, then adjusted to culture results.
• Pain relief and anti-nausea medicine.
• Nothing by mouth, and sometimes a tube through the nose to empty the stomach.

Source control

For secondary peritonitis, the cause must be fixed. Options include:

• Surgery (open or laparoscopic) to remove the appendix, close a perforated ulcer, remove a damaged section of bowel and wash out the abdomen. A temporary stoma may be needed.
• Image-guided drainage of an abdominal abscess with a needle and drain.

SBP and dialysis peritonitis

These are usually treated with antibiotics alone, without surgery. People with cirrhosis also receive IV albumin to protect the kidneys, and often long-term preventive antibiotics afterward. Dialysis peritonitis is often treated with antibiotics added to the dialysis fluid. The catheter may need removing if infection persists.

Complications

• sepsis and septic shock
• abscesses in the abdomen
• acute kidney injury
• adhesions (scar tissue) that can later cause bowel obstruction
• breathing failure, including ARDS
• in cirrhosis, worsening liver and kidney failure

Outlook

With prompt treatment, most people with peritonitis from a burst appendix or perforated ulcer recover fully. The risk of death rises with age, delay in treatment, sepsis and underlying illness. SBP carries a significant risk because it occurs in people with advanced liver disease, and it often prompts referral for liver transplant assessment.

Prevention

• Seek care early for belly pain that is persistent or worsening, before an appendix or ulcer perforates.
• If you have cirrhosis and ascites, ask your doctor whether preventive antibiotics are needed.
• On peritoneal dialysis, follow hand hygiene and exit-site care exactly as trained.
• Limit NSAID use, especially if you have had an ulcer.

Frequently asked questions

What are the first signs of peritonitis?

The first signs are usually belly pain that becomes constant and severe, tenderness to touch, and pain that worsens with movement or coughing. Fever, nausea, vomiting and a swollen belly often follow. In people with cirrhosis or on dialysis, early signs may be milder, such as fever or confusion.

Is peritonitis fatal?

It can be if untreated, because infection spreads into the blood and causes septic shock and organ failure. With rapid antibiotics and surgery, most otherwise healthy people survive and recover fully. Risk is higher in older adults and those with serious underlying illness.

Can peritonitis go away on its own?

No. Peritonitis needs urgent medical treatment. Secondary peritonitis requires antibiotics and usually surgery or drainage to repair the source. Spontaneous bacterial peritonitis is treated with IV antibiotics. Waiting allows infection to spread and greatly increases the risk of death.

How long does it take to recover from peritonitis?

Most people stay in hospital for about 1 to 2 weeks, longer if complications occur. After surgery, full recovery usually takes 4 to 8 weeks. You may need to avoid heavy lifting for several weeks and attend follow-up for stoma reversal if one was created.

What is the difference between peritonitis and appendicitis?

Appendicitis is inflammation of the appendix. If the appendix bursts, infected material spreads into the abdomen and causes peritonitis. Peritonitis is a complication of appendicitis and of many other conditions that perforate or infect abdominal organs.