Encapsulating peritoneal sclerosis is a rare non-malignant cause of acute or subacute small bowel obstruction. It is characterised by total or partial encasement of the small bowel within a thick fibrocollagenous membrane.

Terminology

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.

Epidemiology

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

Clinical presentation

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

Pathology

It can be idiopathic or secondary due to:

• continuous ambulatory peritoneal dialysis (prevalence ~0.7%)

• tuberculosis

• peritoneovenous or ventriculoperitoneal shunts

• treatment with practolol

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

Radiographic features

Plain radiograph

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

Ultrasound

• clumped bowel loops

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

• ascites may be present ⁵

CT

In the appropriate clinical setting, recognition of the entire dilated small bowel at the centre 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 localised fluid collections (especially interbowel)

• bowel wall thickening

• peritoneal or mural calcification

• calcified and/or reactive adenopathy

MRI

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

Differential diagnosis

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