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Sclerosing encapsulating peritonitis

Dr Matt A. Morgan and Radswiki et al.

Sclerosing encapsulating peritonitis (SEP) is a rare benign cause of acute or subacute small bowel obstruction. It is characterized by total or partial encasement of the small bowel within a thick fibrocollagenous membrane.

Terminology

SEP was originally termed abdominal cocoon. It has also been known as sclerosing peritonitis, encapsulating peritonitis, and peritonitis chronica fibrosa incapsulata.

Pathology

SEP can be idiopathic or secondary due to

  • chronic ambulatory peritoneal dialysis
  • peritoneovenous or ventriculoperitoneal shunts
  • treatment with practolol

Various abdominal disorders such as tuberculosis, sarcoidosis, familial Mediterranean fever, gastrointestinal malignancy, protein S deficiency, liver transplantation, fibrogenic foreign material, and luteinized ovarian thecomas are the other rare causes.

Radiographic features

Abdominal radiograph

Radiographic appearances are nonspecific. Radiographs of the abdomen may show

  • air-fluid levels similar to those in patients with any other cause of small-bowel obstruction
  • the wall of the "cocoon" may calcify
CT

In the appropriate clinical setting, recognition of the entire dilated small bowel at the center of the abdomen and encased within a thick fibrocollageneous membrane, as though it were in a cocoon, on a CT image is diagnostic of SEP. The other imaging findings may include signs of obstruction, fixation of intestinal loops, ascites or localized fluid collections, bowel wall thickening, peritoneal or mural calcification, and reactive adenopathy.

Differential diagnosis

SEP may be confused with congenital peritoneal encapsulation, which is characterized by a thin accessory peritoneal sac surrounding the small bowel. 

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