Peritoneum: Anatomy, Function, Conditions and Care
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is the peritoneum?
The peritoneum is a sheet of smooth tissue that lines the abdomen and pelvis and covers many abdominal organs, with a parietal layer, a visceral layer and a cavity between them. It provides padding, lubrication, structure and immune protection. Conditions affecting it include peritonitis, ascites, hernia, adhesions and cancer, most commonly causing abdominal pain and swelling. [1]
What the research says
Peritoneal dialysis and hemodialysis show uncertain differences in survival. A Cochrane review of 84 studies (2 randomized trials and 82 observational studies) found that across 42 studies (700,093 participants), peritoneal dialysis had uncertain effects on the risk of death compared with hemodialysis (RR 0.87, 95% CI 0.77–0.98; very low certainty). In an analysis restricted to the two randomized trials (1,120 participants), peritoneal dialysis may reduce the risk of death (RR 0.53, 95% CI 0.32–0.86; moderate certainty). The authors concluded that the comparison remains uncertain because most data are observational (Ethier et al., Cochrane Database Syst Rev, 2024). [2]
In older adults, peritoneal dialysis may carry a higher mortality risk. A meta-analysis of 31 cohort and case-control studies (more than 774,000 older patients) found a higher mortality rate with peritoneal dialysis than hemodialysis (HR 1.17, 95% CI 1.10–1.25), especially in older people with diabetes or other illnesses and those on dialysis for more than 3 years. Heterogeneity was substantial, and the authors stressed individualized choices (Cheng et al., Gerontology, 2024). [3]
Antibiotic prevention of spontaneous bacterial peritonitis in cirrhosis remains uncertain. A network meta-analysis of 29 randomized trials (3,896 participants) noted that about 2.5% of hospitalizations in people with cirrhosis are for spontaneous bacterial peritonitis. In the trials, about 10% of participants developed it and 15% died, and no antibiotic regimen showed clear differences from no intervention in mortality or in developing the infection (very low-certainty evidence) (Komolafe et al., Cochrane Database Syst Rev, 2020). [4]
Where is the peritoneum located?
The abdominopelvic cavity lies between the diaphragm and the pelvic floor. It includes the abdominal cavity and pelvic cavity. The parietal peritoneum lines the walls of this space, while the visceral peritoneum wraps abdominal organs. [1]
The visceral layer particularly covers the stomach, liver, spleen and parts of the small and large intestines (see the guide to the small intestine). Organs inside the visceral peritoneum are called intraperitoneal. Organs outside it are called retroperitoneal. [1]
Layer or term | Location or meaning |
Parietal peritoneum | Lines the abdominal and pelvic walls. |
Visceral peritoneum | Wraps many abdominal organs. |
Peritoneal cavity | Space between the parietal and visceral layers. |
Intraperitoneal | Describes organs inside the visceral peritoneum. |
Retroperitoneal | Describes organs outside the visceral peritoneum. |
What is the peritoneum made of?
The peritoneum is a serous membrane, meaning it is a type of tissue that secretes serum. This type of lining is generally called mesothelium. It has epithelial cells on the top layer and connective tissue underneath. [1]
The epithelial cells secrete and absorb fluid and filter particles, while the tissue beneath them carries blood vessels, lymph vessels and nerves. The connective tissue holds the structures together, attaches some organs to the abdominal wall and suspends others within the cavity. [1]
What does the peritoneum do?
The peritoneum has several functions, and some are still being studied. It pads organs, helps insulate them and helps hold them in place. Its lubricating fluid reduces friction when movable organs rub against each other. [1]
Ligaments in the peritoneum connect organs to one another and attach the intestines to the back abdominal wall. Blood vessels, lymphatic vessels and nerves run through its layers. [1]
The peritoneum also contributes to immunity. It acts as a barrier to injury and pathogens, recognizes invasive particles, sends white blood cells to target them, filters fluids and drains waste products. The tissue has rapid healing properties that help repair its own injuries. [1]
Function | Role |
Insulation | Fat in the layers warms and protects organs. |
Lubrication | Peritoneal fluid reduces friction between moving organs. |
Structure | Ligaments connect organs and attach the intestines to the back abdominal wall. |
Supply | Blood vessels, lymphatic vessels and nerves run through the layers. |
Immunity | The tissue helps recognize invasive particles, target them with white blood cells, filter fluid and drain waste. |
Healing | The peritoneum has rapid healing properties for its own injuries. |
What are the omentum and mesentery?
The visceral peritoneum folds around organs and creates double layers and pouches. The omentum is a large double layer that covers the front of the abdomen like an apron. The mesentery is a double layer at the back that attaches the intestines to the back abdominal wall. [1]
Fat between the layers provides extra insulation and protection. It also carries neurovascular supply to the organs. [1]
How does the peritoneum sense pain?
The visceral peritoneum covering abdominal organs shares their autonomic nerve supply. It perceives a visceral type of pain that is diffuse and difficult to locate. It can sense stretching when digestive organs expand with food or gas, as well as chemical irritants such as blood or bile leaks. [1]
The parietal peritoneum shares the somatic nerve supply of the abdominal wall it covers. It can perceive more localized pressure, pain and temperature. [1]
Layer | Sensation |
Visceral peritoneum | Diffuse, hard-to-localize pain; stretch; chemical irritants. |
Parietal peritoneum | More localized pressure, pain and temperature. |
What conditions affect the peritoneum?
Conditions that affect the peritoneum include peritonitis, ascites, hernias, abdominal adhesions and sclerosing mesenteritis. [1]
Peritonitis
Peritonitis is inflammation of the peritoneum. An infection inside the peritoneal cavity often causes it, but peritonitis can also be an early indicator of gastrointestinal disease. It is treated as an emergency because infection may be absorbed into the bloodstream and become systemic, a condition called septicemia.
Ascites
Ascites is excess fluid in the peritoneal cavity. It can cause unexplained abdominal swelling. It is usually a symptom of late-stage liver disease, including cirrhosis, which can create high pressure in the portal vein and cause veins to leak. Ascites can also occur with congestive heart failure or cancer. [1]
Hernia
A hernia occurs when tissue from inside one body cavity pushes through a muscle wall into another. Most hernias pass through an abdominal wall, and the peritoneum is the tissue most often involved. Even when a visceral organ protrudes, it is likely wrapped in peritoneum. [1]
Hernias do not usually harm the peritoneum unless the tissue becomes cut off from its blood supply. Some hernias require surgery to repair. [1]
Abdominal adhesions
Abdominal surgery that cuts through the peritoneum can cause tough bands of scar tissue called adhesions. They may not cause problems, but if they form between organs, they can restrict free movement and obstruct movement inside the digestive tract. The most serious risk is bowel obstruction. [1]
Sclerosing mesenteritis
Sclerosing mesenteritis, also called mesenteric panniculitis, affects fatty tissue in the mesentery. It resembles widespread adhesions in the mesentery. For reasons not well understood, chronic inflammation can lead to widespread scarring, or fibrosis. Fibrosis can stop blood flow through the tissue and sometimes cause bowel obstruction. [1]
Mesenteric lymphadenitis
Mesenteric lymphadenitis is inflammation and swelling of lymph nodes in the mesentery. It is usually a symptom of infection. The lymph nodes help filter germs and pathogens when the immune system is activated. It may cause pain and fever but is usually temporary. [1]
Cancer involving the peritoneum
Cancer in abdominopelvic organs can spread to the peritoneum, a process called peritoneal carcinomatosis. Cancer can also begin in the peritoneum. Examples include primary peritoneal cancer and peritoneal mesothelioma. [1]
Pseudomyxoma peritonei is a rare cancer that secretes mucus-like material, which fills the peritoneal cavity. Cancer in the peritoneum can also spread to organs it touches. [1]
Condition | Description |
Peritonitis | Peritoneal inflammation, often from infection; treated as an emergency. |
Ascites | Excess fluid causing unexplained abdominal swelling. |
Hernia | Tissue pushes through an abdominal muscle wall; peritoneum is often involved. |
Abdominal adhesions | Scar-tissue bands that can restrict movement or contribute to bowel obstruction. |
Sclerosing mesenteritis | Chronic mesenteric inflammation and fibrosis that can affect blood flow or bowel movement. |
Mesenteric lymphadenitis | Inflamed mesenteric lymph nodes, usually from infection. |
Peritoneal cancer | Cancer may spread to or originate in the peritoneum. |
What are common symptoms of a peritoneal problem?
Abdominal pain and swelling are the most common symptoms of conditions affecting the peritoneum. Vague or diffuse pain may come from the visceral layer, while more intense pain may indicate irritation of the parietal layer. [1]
Abdominal pain has many causes, so symptoms alone cannot identify a specific condition. Some serious diseases may cause mild or vague symptoms, which is why abdominal pain should be taken seriously.
Symptom pattern | Description |
Abdominal pain | Most common symptom; may be vague, diffuse or more intense. |
Abdominal swelling | Common symptom and may reflect excess fluid. |
Pain with fever | May occur with mesenteric lymphadenitis or infection-related concerns. |
Bowel changes or blockage | May occur with adhesions or mesenteric fibrosis. |
How are peritoneal conditions evaluated?
A healthcare professional may analyze a sample of peritoneal fluid to evaluate peritonitis or ascites. A hollow needle is inserted into the peritoneal cavity to draw a small sample, which is sent to a laboratory. Analysis may identify fluid related to inflammation, leaking blood vessels, infection, cancer or chemicals leaking from an organ. [1]
A peritoneal biopsy may be obtained with a special needle inserted into the abdomen. It may also be taken during a laparoscopy, an exploratory examination that uses a small camera inserted through a small incision. A laparoscopy and biopsy may be suggested when a clinician needs to look inside the abdomen. [1]
Evaluation method | What it may help assess |
Peritoneal fluid analysis | Inflammation, leaking vessels, infection, cancer or chemicals from an organ leak. |
Needle biopsy | A sample of peritoneal tissue. |
Laparoscopy | Direct exploratory examination with a small camera and possible biopsy. |
What treatments involve the peritoneum?
Treatments that involve the peritoneum include peritoneal dialysis, hyperthermic intraperitoneal chemotherapy (HIPEC) and cytoreductive or debulking surgery. [1]
Peritoneal dialysis
Peritoneal dialysis uses the peritoneum’s ability to filter waste products for people living with kidney failure. Dialysis performs some work of the kidneys by removing waste products and excess fluid from blood. During treatment, a fluid solution fills the peritoneal cavity, the peritoneum filters it, and the solution is later drained. [1]
Hyperthermic intraperitoneal chemotherapy
Hyperthermic intraperitoneal chemotherapy, or HIPEC, uses the absorptive properties of the peritoneum. A concentrated, heated chemotherapy solution is delivered directly into the peritoneal cavity for localized cancer. [1]
HIPEC is described as a targeted local approach that differs from traditional chemotherapy delivered systemically through the bloodstream. Treatment suitability and risks require discussion with the treating oncology team.
Cytoreductive or debulking surgery
Cancer in the abdominopelvic cavity is usually treated with surgery as well as chemotherapy. Cytoreductive or debulking surgery attempts to remove as many cancer cells as possible wherever they are found. It may involve removing part or all of the peritoneum, called a peritonectomy. [1]
The omentum is commonly affected because certain cancers tend to spread there first. An omentectomy removes the omentum. [1]
Treatment | Description |
Peritoneal dialysis | Uses a fluid solution and the peritoneum’s filtering function for kidney failure. |
HIPEC | Delivers concentrated, heated chemotherapy directly into the peritoneal cavity for localized cancer. |
Cytoreductive/debulking surgery | Attempts to remove as many cancer cells as possible and may include peritonectomy. |
Omentectomy | Removes the omentum when indicated as part of cancer surgery. |
How can you care for your peritoneal health?
Peritoneal diseases are difficult to predict or prevent. Take abdominal pain seriously and seek medical advice even when you are unsure whether you should be concerned. Symptom severity does not always show how serious a condition is, and some serious diseases may begin with mild or vague symptoms.
There is no substitute for an examination when abdominal pain or swelling is concerning. Keep track of new or persistent symptoms and share relevant history with a healthcare professional. Do not use this article to self-diagnose or decide whether a medical procedure is appropriate.
When should you seek urgent care?
Peritonitis is treated as an emergency because infection in the peritoneal cavity can enter the bloodstream and become systemic. Seek urgent medical assessment for symptoms that could indicate this serious complication. Call 911 or go to the emergency room for severe belly pain that gets worse with movement or touch, a hard or swollen belly, fever or chills, vomiting, or, for people on peritoneal dialysis, cloudy drained fluid with belly pain.
Emergency evaluation is also advised for severe or concerning abdominal symptoms, particularly when infection, bowel obstruction, cancer or another serious condition may be involved. Because symptom severity does not always reflect seriousness, do not delay contacting a healthcare professional simply because symptoms seem mild.
Conclusion
The peritoneum is a layered membrane that lines the abdominopelvic cavity and wraps many abdominal organs. It lubricates and insulates organs, helps hold them in place, carries blood, lymph and nerves, filters fluid, contributes to immune defense and has healing properties.
Its conditions range from peritonitis and ascites to hernias, adhesions, mesenteric disorders and cancer. Abdominal pain and swelling are the most common symptoms, but the type and location of pain can vary by layer.
Take significant or persistent abdominal symptoms seriously and use this guide to prepare questions for a qualified healthcare professional.
Frequently Asked Questions
What is the peritoneum?
The peritoneum is a smooth serous membrane that lines the abdominopelvic cavity and surrounds many abdominal organs.
What is the peritoneal cavity?
The peritoneal cavity is the space between the parietal peritoneum lining the abdominal and pelvic walls and the visceral peritoneum covering organs.
What are the two layers of the peritoneum?
The parietal peritoneum lines the cavity walls, and the visceral peritoneum wraps around abdominal organs.
What does the peritoneum do?
The peritoneum pads and insulates organs, lubricates them, helps hold them in place, carries blood, lymph and nerves, filters fluid, contributes to immune defense and helps heal its own injuries.
What is the omentum?
The omentum is a large double fold of peritoneal tissue covering the front of the abdomen like an apron.
What is the mesentery?
The mesentery is a double layer at the back that attaches the intestines to the back abdominal wall.
What is the difference between visceral and parietal pain?
Visceral peritoneal pain is diffuse and difficult to locate, while parietal peritoneal irritation can cause more localized pressure, pain and temperature sensation.
What is peritonitis?
Peritonitis is inflammation of the peritoneum. An infection in the peritoneal cavity often causes it, and it is treated as an emergency because infection can spread into the bloodstream.
What is ascites?
Ascites is a buildup of excess fluid in the peritoneal cavity that causes unexplained abdominal swelling. It can be associated with liver disease, heart failure or cancer.
What are abdominal adhesions?
Abdominal adhesions are tough bands of scar tissue that can form after abdominal surgery cuts through the peritoneum. They may restrict organ movement and can contribute to bowel obstruction.
Can cancer affect the peritoneum?
Yes. Cancer can spread from an abdominopelvic organ to the peritoneum or begin there.
How is peritoneal fluid tested?
A hollow needle can draw a small sample of fluid from the peritoneal cavity for laboratory analysis.
What is a peritoneal biopsy?
A peritoneal biopsy is analysis of a sample of peritoneal tissue obtained with a special needle or during laparoscopy.
What is laparoscopy?
Laparoscopy is an exploratory examination of the abdominal cavity using a small camera inserted through a small incision.
Why is the peritoneum used in dialysis?
The peritoneum can filter waste products and excess fluid, so a fluid solution can be placed into the peritoneal cavity and later drained as part of peritoneal dialysis.
What is HIPEC?
HIPEC is hyperthermic intraperitoneal chemotherapy, in which a concentrated, heated chemotherapy solution is delivered directly into the peritoneal cavity for localized cancer.
When should I seek care for abdominal pain?
Take abdominal pain seriously and contact a healthcare professional when you are concerned, because symptom severity does not always reflect seriousness. Peritonitis is treated as an emergency, and severe or concerning symptoms need prompt assessment.
Related Reading
Peritonitis: Symptoms, Causes & Treatment — Belly Inflammation Explained explains infection or inflammation of the peritoneum and urgent treatment.
Ascites: Fluid Buildup in the Belly — Causes, Symptoms, Grades, Diagnosis & Treatment (Complete Guide) covers fluid buildup in the peritoneal cavity and how it is treated.
Abdominal Adhesions: Symptoms, Causes, Diagnosis, and Treatment explains scar tissue bands that form inside the belly after surgery.
Peritoneal Dialysis: A Comprehensive Guide to Home-Based Kidney Filtration describes dialysis that uses the peritoneum to filter blood.
References
Cleveland Clinic. Peritoneum: Anatomy, Function, Location & Definition. Cleveland Clinic. Updated April 27, 2022. https://my.clevelandclinic.org/health/body/22894-peritoneum
Ethier I, Hayat A, Pei J, et al. Peritoneal dialysis versus haemodialysis for people commencing dialysis. Cochrane Database Syst Rev. 2024;(6):CD013800. PMID 38899545. https://doi.org/10.1002/14651858.CD013800.pub2
Cheng L, Hu N, Song D, et al. Mortality of Peritoneal Dialysis versus Hemodialysis in Older Adults: An Updated Systematic Review and Meta-Analysis. Gerontology. 2024;70(5):461-478. PMID 38325351. https://doi.org/10.1159/000536648
Komolafe O, Roberts D, Freeman SC, et al. Antibiotic prophylaxis to prevent spontaneous bacterial peritonitis in people with liver cirrhosis: a network meta-analysis. Cochrane Database Syst Rev. 2020;(1):CD013125. PMID 31978256. https://doi.org/10.1002/14651858.CD013125.pub2
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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