Encapsulating peritoneal sclerosis

Last revised by Sonam Vadera on 15 Sep 2023

Encapsulating peritoneal sclerosis 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.

The condition was originally termed abdominal cocoon. The condition is popularly known as sclerosing encapsulating peritonitis, however, this is somewhat of a misnomer as inflammation is not always present 5. It has also been known as sclerosing peritonitis, encapsulating peritonitis, and peritonitis chronica fibrosa incapsulata.

Encapsulating peritoneal sclerosis can occur at any age, with reports ranging from 2-day neonate to 82 years 5.

The presentation is non-specific and patients may present with vomiting, abdominal pain and/or subacute bowel obstruction 5

It can be idiopathic or secondary due to:

Various abdominal disorders such as sarcoidosis, familial Mediterranean fever, gastrointestinal malignancy, ovarian carcinoma 6protein S deficiency, liver transplantation, fibrogenic foreign material, and luteinised ovarian thecomas are other rare causes.

Abdominal radiographic appearances are nonspecific and may be normal or may show:

  • gas-fluid levels similar to those in patients with any other cause of small-bowel obstruction

  • the wall of the "cocoon" may calcify

  • clumped bowel loops

  • trilaminar appearance of a hyperechoic membrane, hypoechoic bowel wall and hyperechoic bowel contents

  • ascites may be present 5

In the appropriate clinical setting, recognition of the entire dilated small bowel at the center of the abdomen and encased within a thick fibrocollagenous membrane, as though it were in a cocoon, is diagnostic of sclerosing encapsulating peritonitis. Other imaging findings may include:

  • enhancing peritoneum, thickened >2 mm 5

  • signs of small intestinal obstruction

  • fixation of intestinal loops

  • ascites or localized fluid collections (especially interbowel)

  • bowel wall thickening

  • peritoneal or mural calcification

  • calcified and/or reactive adenopathy

MRI will demonstrate the same features as CT, although it may better discriminate between thickened bowel and the peritoneal membrane than CT 5

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

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Cases and figures

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