Diseases of the peritoneum
- Lesion
The lining of the abdomen can be inflamed by germs or leaking juices, scarred by fibrosis, or covered by tumours, mostly spread from elsewhere.
What it is
The peritoneum is a single layer of mesothelial cells on thin connective tissue, covering the abdominal viscera and wall. It reacts to infection and chemical irritation (peritonitis), can be encased by fibrosis (sclerosing retroperitonitis), and is a common surface for tumour spread. Primary tumours (mesothelioma, desmoplastic small round cell tumour) are rare; secondary spread (peritoneal carcinomatosis) is common.
Structure
- Peritonitis: neutrophils and fibrinopurulent exudate coating viscera and wall; fluid turns turbid then suppurative.
- Abscesses: subhepatic and subdiaphragmatic collections.
- Except in tuberculous peritonitis, inflammation usually stays superficial.
- Carcinomatosis: many tumour nodules on serosal surfaces, often with ascites; mucinous tumours produce pseudomyxoma.
Step by step
- A hollow viscus perforates or a sterile irritant leaks into the cavity.
- Mesothelial injury and contamination trigger an acute inflammatory response.
- Fibrin and neutrophils coat the surfaces; fluid exudes.
- Fibrin bands wall off the infection: localized abscesses.
- Healing leaves adhesions that can later cause obstruction.
Clinical notes
- Peritonitis causes severe pain, guarding, rigidity and ileus; it can progress to septic shock.
- Tuberculous peritonitis, still seen in Colombia, gives ascites with lymphocytes and caseating granulomas on the peritoneum.
Test yourself
Think of the answer, then tap the question to see it.
In which patients does spontaneous bacterial peritonitis usually occur?
In patients with cirrhosis and ascites, and less often in children with nephrotic syndrome.
What is sclerosing retroperitonitis?
Dense fibrosis of the retroperitoneum (Ormond disease), often part of IgG4-related disease, which can obstruct the ureters.
Which translocation defines desmoplastic small round cell tumour?
t(11;22), producing an EWSR1-WT1 fusion gene.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Septic Peritonitis (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.