Applied Radiology

Diagnosis

Abdominal Cocoon

Findings

A contrast-enhanced CT scan of the abdomen and pelvis showed a markedly distended stomach and proximal small bowel, with the small bowel loops clustered together and displaced into the right upper quadrant and right mid-abdomen (Figure 1). The overlying peritoneum was thickened and pockets of fluid were present in the jejunal mesentery. Intraoperative ultrasound showed clumped small bowel with thickened surrounding peritoneum (Figure 2). Interoperative Findings Exploratory laparotomy revealed a large mass of small bowel surrounded by a thick inflammatory rind with multiple adhesions, encompassing approximately 90% of the bowel. Pathology Lysed pseudocapsule showed dense fibrosis with chronic inflammation and hemorrhage.

Discussion

Abdominal cocoon syndrome is a rare entity that is also known in the literature as sclerosing peritonitis or sclerosing encapsulating peritonitis.1 It is characterized by partial or complete encasement of small bowel by a thick rind of fibrous tissue and adhesions, causing clustering of the bowel. Occasionally, the large bowel, stomach, or other abdominal organs may be involved.2 Clinically, the condition may present with vague abdominal pain and weight loss. For patients who are on chronic ambulatory peritoneal dialysis (CAPD), there is a loss of ultrafiltration capacity and a bloody dialysis effluent. However, early clinical features of sclerosing peritonitis are generally nonspecific and are frequently not recognized until the patient develops partial or complete small bowel obstruction.3 The characteristic radiologic findings of sclerosing peritonitis have been sparsely described. Ultrasound may show clumping of bowel loops with the bowel surrounded by a thick rim of hypoechoic tissue. Tethering of the bowel posteriorly, or the presence of a membrane anterior to the small bowel may be seen.1,4 Barium studies show varying length of small bowel tightly enclosed in a thickened peritoneum, proximal small bowel dilation, and an increase in transit time.5 The CT findings may also include an encapsulated clump of bowel, peritoneal thickening, calcification, peritoneal enhancement, small bowel tethering, and loculated fluid collections.1,3 Peritoneal calcification and tethering of the small bowel loops are associated more specifically with sclerosing peritonitis than the other CT findings.6 Multiple etiologies for abdominal cocoon have been established, although the underlying pathogenesis is not fully understood. It may occur as a serious complication of CAPD.5 It has also been described in association with prolonged practolol therapy, sarcoidosis, systemic lupus erythematosus, indwelling abdominal catheters (specifically Le-Veen shunts), orthotopic liver transplantation, and tuberculous pelvic inflammatory disease.1,7-10 These conditions may predispose patients to peritoneal irritation and inflammation, which as a final effect leads to peritoneal fibroneogenesis. Primary idiopathic abdominal cocoon is rare and has been mainly described in young girls from tropical regions.11 Retrograde menstruation causing peritoneal irritation has been speculated as the possible cause in these cases. In a recent literature review, only four idiopathic cases in males have been reported.1 Peritoneal encapsulation may have a similar appearance to abdominal cocoon on radiologic studies. This is a congenital condition in which all or part of the small bowel is encased by an accessory peritoneal membrane. Usually, this is asymptomatic, but has been reported to cause bowel obstruction in a few cases. Pathologically, the encasing membrane is normal peritoneum rather than the thick fibrous-collagenous tissue seen in abdominal cocoon.12 CONCLUSION Although abdominal cocoon is an unusual cause of small bowel obstruction, it can be diagnosed preoperatively as it may have a distinct appearance on CT of clumped bowel loops encased by a thick membrane. It most commonly occurs in patients on CAPD or in adolescent girls in the tropics, but rarely can occur in the absence of medical or surgical risk factors, as in this case. 1. Deeb LS, Mourad FH, El-Zein YR, Uthman SM. Abdominal cocoon in a man: Preoperative diagnosis and literature review. J Clin Gastroenterol. 1998;26:148-150. 2. Wig JD, Gupta SK. Computed tomography in abdominal cocoon. J Clin Gastroenterol. 1998;27:259-260. 3. Korzets A, Korzets Z, Peer G, et al. Sclerosing peritonitis. Possible early diagnosis by computerized tomography of the abdomen. Am J Nephrol. 1988;8:143-146. 4. Hollman AS, McMillan MA, Briggs JD, et al. Ultrasound changes in sclerosing peritonitis following continuous ambulatory peritoneal dialysis. Clin Radiol. 1991;43:176-179. 5. Holland P. Sclerosing encapsulating peritonitis in chronic ambulatory peritoneal dialysis. Clin Radiol. 1990;41:19-23. 6. Stafford-Johnson DB, Wilson TE, Francis IR, et al. CT appearance of sclerosing peritonitis in patients on chronic ambulatory peritoneal dialysis. J Comput Assist Tomogr. 1998;22:295-299. 7. Cheijfec G, Reyes C, Stanley MM, et al. Diffuse peritoneal fibromatosis associated with perioneo-venous shunt in patients with cirrhosis [abstract]. Lab Invest. 1983;48:15A. 8. Hunt D, Frew JL. Pericarditis and peritonitis associated with practolol therapy [letter]. Br Med J. 1975;1:92-93. 9. Maguire D, Srinivasan P, O'Grady J, et al. Sclerosing encapsulating peritonitis after orthotopic liver transplantation. Am J Surg. 2001;182:151-154. 10. Lalloo S, Krishna D, Maharajh J. Case report: Abdominal cocoon associated with tuberculous pelvic inflammatory disease. Br J Radiol. 2002;75:174-176. 11. Sieck JO, Cowgill R, Larkworthy W. Peritoneal encapsulation and abdominal cocoon. Case reports and a review of the literature. Gastroenterology. 1983;84:1597-1601. 12. Casas JD, Mariscal A, Martinez N. Peritoneal encapsulation: CT appearance. AJR Am J Roentgenol. 1998;171:1017-1019.