[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Gastrointestinal tract](https://durgical.com/en/general-pathology/areas/gi/) › Diseases of the peritoneum # 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. Updated Nov 12, 2026 ## Key points - Bacterial peritonitis usually follows perforation; E. coli, streptococci, Staphylococcus aureus, enterococci and Clostridium perfringens. - Spontaneous bacterial peritonitis: no source, usually cirrhosis with ascites (children with nephrotic syndrome); neutrophils in ascitic fluid, E. coli, streptococci, Klebsiella. - Sterile chemical peritonitis: bile, pancreatic enzymes (with fat necrosis), blood (endometriosis), keratin from a ruptured dermoid cyst, foreign material (talc, sutures: foreign-body granulomas). - Sclerosing retroperitonitis (Ormond disease): dense retroperitoneal fibrosis, often in the IgG4-related disease spectrum; can trap the ureters. - Peritoneal mesothelioma: heavy asbestos exposure. - Desmoplastic small round cell tumour: children and young adults; t(11;22) EWSR1-WT1. ## 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. ## Memory aid Holes, juices, blood and foreign stuff inflame the peritoneum; asbestos and other tumours seed it. ## 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. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/diseases-of-the-peritoneum/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Connections ## Related 7 - [Acute appendicitis](https://durgical.com/en/general-pathology/acute-appendicitis/) - [Sigmoid diverticular disease](https://durgical.com/en/general-pathology/sigmoid-diverticular-disease/) - [Peptic ulcer](https://durgical.com/en/general-pathology/peptic-ulcer/) - [Tumours of the appendix](https://durgical.com/en/general-pathology/tumours-of-the-appendix/) - [Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer](https://durgical.com/en/general-pathology/patterns-of-acute-inflammation-serous-fibrinous-purulent-abscess-ulcer/) - [Pathways of spread and the usual metastatic sites](https://durgical.com/en/general-pathology/pathways-of-spread-and-the-usual-metastatic-sites/) - [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/) ## Related conditions 11 - [Peritonitis](https://durgical.com/en/conditions/peritonitis/) - [Ascites and spontaneous bacterial peritonitis](https://durgical.com/en/conditions/ascites-and-spontaneous-bacterial-peritonitis/) - [Intra-abdominal abscess](https://durgical.com/en/conditions/intra-abdominal-abscess/) - [Acute pancreatitis](https://durgical.com/en/conditions/acute-pancreatitis/) - [Ovarian cancer](https://durgical.com/en/conditions/ovarian-cancer/) - [Malignant pleural mesothelioma](https://durgical.com/en/conditions/malignant-pleural-mesothelioma/) - [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/) - [Acute appendicitis](https://durgical.com/en/conditions/acute-appendicitis/) - [Diverticular disease and diverticulitis](https://durgical.com/en/conditions/diverticular-disease-and-diverticulitis/) - [Peptic ulcer disease](https://durgical.com/en/conditions/peptic-ulcer-disease/) - [Gastric cancer](https://durgical.com/en/conditions/gastric-cancer/) [← All of general pathology](https://durgical.com/en/general-pathology/) 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](https://www.ncbi.nlm.nih.gov/books/NBK526129/) (StatPearls (NCBI Bookshelf), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/diseases-of-the-peritoneum/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/diseases-of-the-peritoneum/