Sclerosing encapsulating peritonitis

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.
Originally termed abdominal cocoon and is also known as sclerosing peritonitis, encapsulating peritonitis, and peritonitis chronica fibrosa incapsulata.

Pathophysiology

SEP can be idiopathic or mainly secondary to chronic ambulatory peritoneal dialysis, peritoneovenous or ventriculoperitoneal shunts, or 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 causative factors.

Radiographic features

Plain film

Plain film appearences are non specific. Radiographs of the abdomen can show air-fluid levels similar to those in patients with any other cause of small-bowel obstruction.

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.