Cap polyposis

Cap polyposis is an extremely rare, non-neoplastic disorder of the gastrointestinal tract characterized by the development of inflammatory polyps predominantly in the rectum and sigmoid colon. The polyps are distinctive in that they are covered by a 'cap' of fibrinopurulent (containing fibrin and pus) exudate overlying granulation tissue, which gives the condition its name. The underlying mucosa between polyps is typically normal. Cap polyposis is not considered a premalignant condition, and the ICD-10 classification under D12.6 (benign neoplasm of colon, unspecified) reflects its polypoid nature rather than true neoplastic potential. Patients with cap polyposis commonly present with chronic mucous diarrhea, rectal bleeding, tenesmus (a persistent urge to evacuate the bowels), and protein-losing enteropathy, which can lead to hypoalbuminemia and associated complications such as peripheral edema. Abdominal pain and straining during defecation are also frequently reported. The condition can affect individuals across a wide age range, though it is most commonly diagnosed in adults. The exact cause remains unknown, but abnormal colonic motility and mucosal prolapse are thought to play a role in its pathogenesis. Treatment of cap polyposis is not standardized due to its rarity. Management strategies that have been reported include endoscopic polypectomy, eradication of Helicobacter pylori infection (which has led to remission in some cases), corticosteroid therapy, metronidazole, infliximab, and in refractory cases, surgical resection of the affected bowel segment. Avoidance of straining and treatment of any underlying motility disorder may also be beneficial. Recurrence after treatment is possible, and long-term follow-up is recommended.

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