Peritonitis: Symptoms, Causes & Treatment — Belly Inflammation Explained
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR
Peritonitis is a serious condition that starts in the abdomen — the area of the body between the chest and the pelvis. It happens when the peritoneum, the thin layer of tissue lining the inside of the abdomen, becomes inflamed, usually due to an infection from bacteria or fungi. There are two types: spontaneous bacterial peritonitis (linked to liver disease such as cirrhosis or to kidney disease) and secondary peritonitis (caused by a hole or rupture in an organ such as the stomach or colon, or by other health conditions). Common symptoms include severe belly pain or tenderness, bloating, fever, vomiting, loss of appetite, and in some cases confusion. Peritonitis is usually treated in the hospital with antibiotics — sometimes given through a vein — and often with surgery to remove infected tissue and treat the cause. Without fast treatment, peritonitis can spread into a whole-body infection called sepsis, which can cause shock, organ failure, and death. People who use peritoneal dialysis can prevent much of their peritonitis risk with careful hygiene around the catheter.
Quick Answer: What Is Peritonitis?
Peritonitis is a serious condition in which the peritoneum — the thin lining of the abdomen — becomes inflamed.
It usually happens due to an infection from bacteria or fungi.
The two types are spontaneous bacterial peritonitis (often linked to liver cirrhosis or kidney disease) and secondary peritonitis (usually caused by a rupture in an organ or by other health conditions).
Common symptoms include belly pain or tenderness, bloating, fever, vomiting, loss of appetite, reduced urine, and sometimes confusion.
People on peritoneal dialysis may also notice cloudy dialysis fluid or white flecks, strands, or clumps (fibrin) in it.
Diagnosis combines a medical history, physical exam, blood tests, imaging (X-ray, ultrasound, CT), and peritoneal fluid analysis.
Treatment usually means a hospital stay with IV antibiotics, surgery when a rupture is involved, and supportive care; without treatment, peritonitis can cause sepsis and be deadly.
What Is Peritonitis?
Peritonitis is a serious condition that starts in the abdomen — the area of the body between the chest and the pelvis. It happens when the thin layer of tissue inside the abdomen becomes inflamed. This tissue layer is called the peritoneum.
Peritoneum: the thin layer of tissue that lines the inside of the abdomen and covers the abdominal organs.
Peritonitis usually happens due to an infection from bacteria or fungi. There are two main types:
Type | What it is |
Spontaneous bacterial peritonitis | An infection caused by bacteria that can happen when someone has liver disease, such as cirrhosis, or kidney disease — without a hole or tear in an organ |
Secondary peritonitis | Peritonitis that happens due to a hole (rupture) inside an organ in the abdomen, or that is caused by other health conditions |
It is important to get treatment fast. Healthcare professionals have ways to clear out the infection and can also treat any medical problem that might be causing it. If you do not get treatment, peritonitis can lead to a serious infection that spreads through the body — it can be deadly.
What Are the Symptoms of Peritonitis?
Symptoms of peritonitis include:
Symptom | What it looks like |
Belly pain or tenderness | Often the most striking symptom; can be so severe that you cannot sit still or find a comfortable position |
Bloating or fullness | A feeling of fullness in the abdomen |
Fever | Elevated body temperature |
Upset stomach and vomiting | Nausea with vomiting |
Loss of appetite | Reduced desire to eat |
Diarrhea | Loose stools |
Reduced urine | Urinating less than usual |
Thirst | Unusual thirst |
Not able to pass stool or gas | Bowel movements and gas cannot pass |
Feeling tired | Unusual fatigue |
Confusion | Especially in older adults or people with liver disease |
If you use peritoneal dialysis (a treatment for kidney failure described below), peritonitis symptoms may also include:
Dialysis-related sign | What it looks like |
Cloudy dialysis fluid | The fluid looks cloudy or has an unusual color |
Fibrin in the fluid | White flecks, strands, or clumps in the dialysis fluid — these clumps are called fibrin |
What Causes Peritonitis?
Peritonitis usually starts when germs reach the peritoneum. Most often this happens because of a hole (rupture) in an organ in the abdomen, such as the stomach or colon. It is rare for peritonitis to happen for other causes.
Ruptures and Holes
Common causes of a hole that leads to peritonitis include:
Cause | How it leads to peritonitis |
Ruptured appendix, stomach ulcer, or hole in the colon | These conditions allow bacteria to get into the peritoneum through a hole in the digestive tract |
Pancreatitis | Inflammation of the pancreas — a gland in the abdomen; if you have pancreatitis and get an infection, bacteria could spread outside the pancreas and lead to peritonitis |
Diverticulitis | Infection of small, bulging pouches in the digestive tract; if one pouch breaks open, it can spill waste from the intestine into the abdomen |
Trauma | Injury may cause peritonitis by allowing bacteria or chemicals from other parts of the body to get into the peritoneum |
Medical Procedures
Several medical procedures can also lead to peritonitis, most notably peritoneal dialysis — a treatment for kidney failure that uses tubes, called catheters, to remove waste products from the blood. An infection may happen during peritoneal dialysis due to an unclean treatment room, poor hygiene, or tainted equipment.
Other procedure-related causes include:
Procedure | Risk level |
Digestive surgery | Peritonitis may happen after surgery on the digestive tract |
Feeding tubes | Use of feeding tubes can lead to peritonitis |
Fluid removal from the abdomen | Such as for ascites (fluid buildup) in liver disease |
Colonoscopy | An exam to check inside the rectum and colon; peritonitis is a rare complication |
Endoscopy | A procedure to check the digestive tract; also rare |
Spontaneous Bacterial Peritonitis
Peritonitis that happens without a hole or tear is called spontaneous bacterial peritonitis. It is usually a complication of liver disease, such as cirrhosis. Advanced cirrhosis causes a lot of fluid buildup in the abdomen, and that fluid buildup could lead to a bacterial infection.
Who Is Most at Risk?
Some things that raise the risk of peritonitis are:
Risk factor | Why it raises risk |
Peritoneal dialysis | Peritonitis can happen in people who get this treatment, usually due to germs around the catheter |
Liver cirrhosis | Fluid buildup in the abdomen can become infected |
Appendicitis | A rupture spreads bacteria into the abdomen |
Stomach ulcers | A hole in the stomach wall lets bacteria escape |
Diverticulitis | A burst pouch spills intestinal waste into the abdomen |
Crohn's disease | Raises the risk of holes and inflammation in the digestive tract |
Pancreatitis | Infection can spread outside the pancreas |
History of peritonitis | Once you have had peritonitis, your risk of getting it again may be higher than someone who has never had it |
What Complications Can It Cause?
Without treatment, peritonitis may cause a whole-body infection called sepsis. Sepsis is very dangerous. It can cause shock, organ failure, and death.
How Is Peritonitis Diagnosed?
To diagnose peritonitis, your healthcare professional talks with you about your medical history and gives you a physical exam. Your symptoms alone may be enough to diagnose the condition if your peritonitis is linked to peritoneal dialysis.
If more tests are needed to confirm a diagnosis, your healthcare professional may suggest:
Test | What it involves | What it shows |
Blood tests | A blood sample is taken to check for an increase in disease-fighting white blood cells; a blood culture may test for bacteria in the blood | An increased white blood cell count is usually a sign of infection or inflammation |
X-ray | An imaging exam of the abdomen | Can check for holes or other tears in the digestive tract |
Ultrasound | A test that uses sound waves to make images inside the body | Looks for fluid, tears, or inflammation |
CT scan | Detailed cross-sectional imaging of the abdomen | Used in some cases to locate the source of infection |
Peritoneal fluid analysis | A thin needle takes a sample of the fluid in the peritoneum; more likely if you use peritoneal dialysis or have fluid in the abdomen from liver disease | An increased white blood cell count in this fluid usually points to infection or inflammation; a culture of the fluid may spot bacteria |
How Is Peritonitis Treated?
Peritonitis requires prompt medical attention, and both main types are treated in the hospital.
Spontaneous Bacterial Peritonitis
Spontaneous bacterial peritonitis can be life-threatening. You will need to stay in the hospital. Treatment includes antibiotics. It also includes supportive care to ease your symptoms.
Secondary Peritonitis
You will also need to stay in the hospital for secondary peritonitis. Treatment may include:
Treatment | What it involves |
Antibiotics | You will likely take antibiotic medicine through a needle in a vein (IV). This clears out the infection and keeps it from spreading. The type of antibiotic and how long you take it vary depending on how serious your condition is and the kind of peritonitis you have |
Surgery | Often needed to remove infected tissue, treat the cause of the infection, and prevent the infection from spreading. Surgery is important if your peritonitis is due to a ruptured appendix, stomach, or colon |
Other treatments | Depending on your symptoms, hospital care will likely include pain medicines, fluids given through a tube (intravenous fluids), oxygen, and in some cases a blood transfusion |
If You Use Peritoneal Dialysis
If you have peritonitis, your healthcare professional may suggest that you receive dialysis in another way. You may need this other type of dialysis for several days while your body heals from the infection. If your peritonitis lingers or comes back, you may need to stop having peritoneal dialysis completely and switch to a different type of dialysis.
How Can You Prevent Peritonitis?
Peritonitis linked with peritoneal dialysis is often caused by germs around the catheter. If you use peritoneal dialysis, take these steps to prevent peritonitis:
Prevention step | How to do it |
Wash your hands | Before you touch the catheter; scrub under your fingernails and between your fingers |
Clean the skin around the catheter | Use an antiseptic every day |
Store your supplies | Keep them in a clean place |
Wear a surgical mask | During your dialysis fluid exchanges |
Talk with your dialysis care team | Discuss the correct care for your peritoneal dialysis catheter |
Your healthcare professional may also prescribe antibiotics to prevent peritonitis, especially if you have had peritonitis before. Antibiotics also might be prescribed if you have a buildup of peritoneal fluid due to a medical condition such as liver cirrhosis. If you take medicine called a proton pump inhibitor, you may be asked to stop taking it.
When Should You See a Doctor?
Peritonitis can be life-threatening if you do not get treatment quickly.
Situation | What to do |
Severe pain or tenderness of your abdomen along with bloating or fullness, plus fever, upset stomach and vomiting, reduced urine, thirst, or inability to pass stool or gas | Call your healthcare professional right away |
Cloudy dialysis fluid, unusual color, white flecks, strands or clumps, or unusual smell — especially if the area around your catheter changes color or is painful | Call your healthcare professional right away |
Severe belly pain after a burst appendix or serious abdominal injury | Get medical help right away; it may feel so bad that you cannot sit still or find a comfortable position |
Severe belly pain after an accident or injury | Call 911 or get emergency medical care |
Preparing for Your Appointment
If peritonitis is suspected, you will likely go straight to a hospital emergency department rather than scheduling a routine appointment — this is a condition where speed matters. If you are managing a related condition such as liver disease or use peritoneal dialysis, bring the following to any appointment:
What to bring | Why it helps |
A list of your symptoms and when they began | Helps the team trace the cause |
Details of your dialysis care | What type you use, how often you exchange fluid, and your catheter care routine |
Your medical history | Especially liver cirrhosis, kidney disease, digestive conditions, or prior peritonitis |
All medicines, vitamins, and supplements with doses | Including any proton pump inhibitors |
Questions to ask | Such as what caused the infection, what tests are needed, and how to prevent it from recurring |
Conclusion
Peritonitis is a serious, potentially life-threatening inflammation of the peritoneum — the thin lining of the abdomen — usually caused by bacteria or fungi. It comes in two forms: spontaneous bacterial peritonitis, often tied to liver cirrhosis or kidney disease, and secondary peritonitis, typically caused by a rupture in the appendix, stomach, or colon, by pancreatitis, diverticulitis, trauma, or medical procedures such as peritoneal dialysis.
The warning signs are hard to miss when you know them: severe belly pain or tenderness, bloating, fever, vomiting, loss of appetite, and sometimes confusion or cloudy dialysis fluid in people using peritoneal dialysis. Diagnosis combines a history, physical exam, blood tests, imaging, and peritoneal fluid analysis. Treatment almost always means a hospital stay with IV antibiotics, often surgery to repair ruptures and remove infected tissue, and supportive care. Without treatment, peritonitis can progress to sepsis — a whole-body infection that can cause shock, organ failure, and death. For people on peritoneal dialysis, careful hand hygiene, daily catheter-site cleaning, and following prevention steps prescribed by the care team substantially reduce the risk.
If you have severe belly pain, fever, or bloating — especially after an injury or if you use peritoneal dialysis — seek emergency medical care right away. Every hour counts.
Frequently Asked Questions
What is peritonitis?
Peritonitis is a serious condition that starts in the abdomen and happens when the peritoneum — the thin layer of tissue lining the inside of the abdomen — becomes inflamed. It usually happens due to an infection from bacteria or fungi.
What does peritonitis feel like?
Peritonitis usually causes belly pain or tenderness — often so severe that you cannot sit still or find a comfortable position — along with bloating or fullness, fever, upset stomach and vomiting, loss of appetite, diarrhea, reduced urine, thirst, inability to pass stool or gas, fatigue, and sometimes confusion.
What causes peritonitis?
Peritonitis is usually caused by a hole (rupture) in an organ in the abdomen, such as the stomach or colon — for example, a ruptured appendix, stomach ulcer, or hole in the colon. It can also follow digestive surgery, feeding tube use, trauma, pancreatitis, diverticulitis, or peritoneal dialysis. Peritonitis without a hole is called spontaneous bacterial peritonitis and is usually a complication of liver cirrhosis or kidney disease.
Is peritonitis life-threatening?
It can be. Peritonitis can be life-threatening without quick treatment. Without treatment, it may cause sepsis — a whole-body infection that can cause shock, organ failure, and death.
How is peritonitis treated?
Treatment usually requires a hospital stay. It includes antibiotics — often given through a vein — plus supportive care such as pain medicines, IV fluids, and oxygen. Surgery is often needed to remove infected tissue and treat the cause, especially when peritonitis comes from a ruptured appendix, stomach, or colon.
Can peritonitis come back?
Yes. Once you have had peritonitis, your risk of getting it again may be higher. Healthcare professionals may prescribe preventive antibiotics in some cases, and people on peritoneal dialysis who have recurring peritonitis may need to switch to a different type of dialysis.
How do you prevent peritonitis during peritoneal dialysis?
Peritonitis linked with dialysis is often caused by germs around the catheter. Preventive steps include washing hands thoroughly before touching the catheter, cleaning the skin around the catheter with an antiseptic daily, storing supplies in a clean place, wearing a surgical mask during fluid exchanges, and talking with the dialysis care team about correct catheter care.
When should I go to the emergency room for belly pain?
Call 911 or get emergency medical care if you have severe belly pain after an accident or injury. Get medical help right away if the pain is so bad that you cannot sit still or find a comfortable position, or if severe belly pain is accompanied by fever, vomiting, bloating, or inability to pass stool or gas.
Related Reading
Sources
Peritonitis — Symptoms & Causes. Clinical reference page, dated August 8, 2025. https://www.mayoclinic.org/diseases-conditions/peritonitis/symptoms-causes/syc-20376247
Peritonitis — Diagnosis & Treatment. Clinical reference page, dated August 8, 2025. https://www.mayoclinic.org/diseases-conditions/peritonitis/diagnosis-treatment/drc-20376250
This article is for general informational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about any medical condition.
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