What causes abdominal cocoon sign in the abdomen on CT imaging?
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Answer: Abdominal cocoon sign represents encapsulation of bowel loops by a thick fibrotic or fibrocartilaginous membrane. The condition is either primary (idiopathic) or secondary (acquired). Secondary cases are often associated with prolonged peritoneal dialysis. The underlying pathological process involves increased release of fibrogenic cytokines leading to fibrin-like material deposition on the peritoneum, resulting in progressive encapsulation that may be partial or complete. This encapsulation causes intermittent episodes of bowel obstruction due to mechanical compression and fixation of intestinal loops.
Why is it called so?:
The sign is named for its appearance on imaging and surgical inspection, where the bowel loops appear wrapped or encased within a thick fibrotic membrane resembling a cocoon that envelops and protects the bowel within.
Pathophysiology:
The condition develops through aberrant peritoneal fibrotic response characterized by excessive fibrogenic cytokine release. This pathological process leads to deposition of fibrin-like material on the visceral and parietal peritoneum. Progressive fibrosis results in formation of a thick, restrictive fibrous membrane that encases bowel loops. The encapsulation restricts normal bowel mobility and peristalsis, causing mechanical obstruction. Bowel loops become fixed in position, clustered centrally, with associated mural thickening, peritoneal thickening, and potential calcification. The membrane creates alternating areas of firm consistency overlying the dense fibrous capsule and soft areas corresponding to thin-walled distended small intestine.
Alternative names: Encapsulating peritoneal sclerosis, sclerosing encapsulating peritonitis, abdominal cocoon syndrome
Other associated named signs: Cauliflower sign – broad head formed by bowel loops with narrow mesenteric apex; Bottle gourd sign – dilatation of duodenal portions with encasement of distal duodenum and jejunal loops; Clumping sign – clustering and conglomeration of bowel loops in center of abdomen
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