Contrast enhanced CT is the primary tool for diagnosing EPS

How to suspect cocoon?

• Peripherally arranged clustered bowel loops in a fixed concertina-like configuration (Fig 1)
• A thin membrane encasing the bowel loops: Thickened peritoneum (~2mm) with marked continuous enhancement: The “trilaminar” membrane appearance at US has been described
• Angulation, kinking, and tethering of the bowel loops (Fig 2)
• Small bowel feces sign without any identifiable luminal / mural / vascular cause

Etiology and complications of cocoon with cases-

•  Primary form – idiopathic
• Secondary form-
  • Peritoneal dialysis
  • Laparotomy for carcinoma or benign disorder
  • Surgical/Ventriculoperitoneal shunt
  • Bacterial/tubercular peritonitis
  • Malignancies with serosal deposits- ovarian, gastric, renal, pancreatic
  • Beta blockers
  • Radiation enteritis
  • Trauma
• Presence of ascites, omental thickening, nodular serosal deposits, peritoneal calcifications may help to identify etiology
• Bowel and mesenteric encasement in a closed compartment may lead to bowel obstruction, gangrene and perforation

Primary/Idiopathic abdominal cocoon

• Relatively rare cause of intestinal obstruction and is found predominantly in adolescent girls
• Small-bowel loops appear congregated toward the center of the abdominal cavity and are encased by a mantle that demonstrates soft-tissue attenuation (Fig 3)- diagnostic of cocoon
• Usually the proximal small bowel is involved; thus patients present with gastroduodenal distension
• Angulation, kinking, and tethering of the bowel loops indicate extensive inter-bowel adhesions, which portend a poor prognosis
• Etiology hypothesized -retrograde menstruation with a superimposed viral infection, retrograde peritonitis and cell-mediated immunological tissue damage incited by gynecological infection

Tubercular abdominal cocoon

• Tubercular EPS
• 3 types of peritoneal TB described
  • Wet- free/loculated ascites (Fig 4)
  • Dry- mesenteric thickening, lymphadenopathy and fibrous adhesions creating a “plastic abdomen”
  • Mixed/fibrotic-omental thickening and matted bowel loops (Fig 12,13)
• Low attenuation necrotic nodes
• Complications include abscess formation, bands and adhesions causing obstruction (Fig 13,14 )

Peritoneal dialysis related abdominal cocoon 

• Serious, life-threatening complication in patients on long-term peritoneal dialysis (PD)
• Thickening and sclerosis of the peritoneal membrane with extensive adhesion of intraperitoneal organs, which results in decreased ultrafiltration and eventually in bowel obstruction with ileus symptoms
• CT features include peritoneal calcification, bowel wall thickening, peritoneal thickening, loculated fluid collections, and tethered bowel loops (Fig 5)
• Risk factors include duration of PD, recurrent episodes of PD peritonitis, and exposure to hypertonic glucose-containing peritoneal solutions

Malignancy related abdominal cocoon formation 

• Peritoneal metastases from common primaries can cause omental and serosal deposits and rarely cocoon formation ( Fig 6-8)
• Commonly implicated malignancies include:
• ovarian cancer
• gastric cancer
• esophageal cancer
• colorectal cancer

Surgery / Trauma as a cause of abdominal cocoon 

• Post-op period is associated with enhanced collagen production and subsequent fibrosis
• Efforts to divide adhesions may further precipitate and increase their formation
• Adhesion and bands can cause obstruction (Fig 9,10)
• Association of internal herniation and abdominal cocoon syndrome is an extremely rare cause of mechanical intestinal obstruction
• Rarely, trauma can incite peritoneal inflammation, leading onto EPS (Fig 11)

Trauma as etiology of EPS

Hyperdense hematoma in omentum with associated omental thickening and cocoon formation around the bowel loop may form post trauma ( Fig 11)

Complications

Abdominal cocooncan lead to complications such as bowel obstruction (Fig 12,13) due to dense fibrotic adhesions restricting intestinal movement, ischemia and gangrene (Fig 12) from strangulated bowel loops, and perforation (Fig 14) resulting in peritonitis and sepsis, requiring urgent medical intervention.

Mimickers

• Peritoneal carcinomatosis can demonstrate thickening and abnormal enhancement of the peritoneum (Fig 15)
• Internal hernias may demonstrate abnormal clustering of bowel loops. Usually no sac is discernible( Fig 16)

Limitations

• Rare nature of abdominal cocoon and its nonspecific symptoms make early detection difficult.
• Some cases are only identified during surgery, and sometimes internal hernias pose a diagnostic challenge