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AJR 2004; 183:1658-1660
© American Roentgen Ray Society


Case Report

CT Findings of an Abdominal Cocoon

Santosh Gupta1, R. G. Shirahatti2 and Joshi Anand3

1 Department of Radiology (CT/MR), P. D. Hinduja Hospital, Mahim, Mumbai 400 016, India.
2 Department of Surgery, P. D. Hinduja Hospital, Mumbai 400 016, India.
3 Department of Gastroenterology, P. D. Hinduja Hospital, Mumbai 400 016, India.

Received September 8, 2003; accepted after revision February 16, 2004.

 
Address correspondence to S. Gupta.


Introduction
Top
Introduction
Case Report
Discussion
References
 
The abdominal cocoon, also referred to as sclerosing encapsulating peritonitis, is a relatively rare cause of intestinal obstruction characterized by fibrotic encapsulation of the bowel. The encapsulation may be total or partial. We report a case of a patient who presented with a mild intestinal obstruction and who showed typical CT findings of an abdominal cocoon, which was diagnosed preoperatively on a CT scan and confirmed at surgery. To our knowledge, only a few cases of this entity have been reported previously [1].


Case Report
Top
Introduction
Case Report
Discussion
References
 
A 56-year-old man with chronic alcoholism was admitted to our institution with symptoms suggestive of acute intestinal obstruction. He had experienced colicky pain in the infraumbilical region for 5 days in addition to vomiting and constipation. He had no previous history of similar complaints, trauma to the abdomen, or symptoms suggestive of bowel perforation or peritonitis.

At physical examination, his abdomen was not tender, but the umbilical area was distended. On palpation, a soft mass approximately 6–8 cm in diameter was found in the umbilical region. Some firm areas were palpated in the mass. It was mobile at right angles to the axis of the mesentery. Bowel sounds were hyperperistaltic. The results of a rectal examination were unremarkable. After a period of conservative treatment, the patient seemed to improve clinically. However, after resuming oral feeding, his symptoms returned.

CT scans were obtained in which a conglomerate of several small-bowel loops (both jejunal and ileal) was seen in the center of the abdomen (Figs. 1A, 1B, 1C). A thick enhancing membrane surrounded the bowel, forming a saclike structure or a cocoon (Figs. 1B and 1C). Mild fluid was seen between these encapsulated bowel loops, some of which were closely apposed and probably adhered to each other. On the CT scans of the upper abdomen, the duodenum and a part of adjacent jejunum showed mild dilatation, beyond which the jejunal loop was seen to be extending into the cocoon. We suspected narrowing and obstruction with mild proximal dilatation at this site (Fig. 1A). No oral contrast material was seen in the colon beyond the cocoon. However, no delayed CT scans were obtained, so we do not know whether there was complete or only partial obstruction. The CT findings were consistent with sclerosing encapsulating peritonitis forming an abdominal cocoon. Within the cocoon, the small bowel showed mild prominence. The abdominal cocoon appeared to cause a closed-loop obstruction. Although the patient did not give any history of previous surgery at the time of the CT examination, when asked after the examination, he gave a history of some surgery that had been performed several years earlier for intestinal perforation, the details of which were not available.



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Fig. 1A. 56-year-old man with abdominal cocoon. Contrast-enhanced CT scan obtained through upper abdomen shows mild dilatation of duodenum and proximal jejunal loop at site of entry into encapsulated saclike structure.

 


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Fig. 1B. 56-year-old man with abdominal cocoon. Contrast-enhanced CT scans of abdomen obtained caudad to A show conglomerate of multiple small-bowel loops seen in center of abdomen, surrounded by thick enhancing saclike structure. Evidence of fluid collection between bowel loops is seen.

 


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Fig. 1C. 56-year-old man with abdominal cocoon. Contrast-enhanced CT scans of abdomen obtained caudad to A show conglomerate of multiple small-bowel loops seen in center of abdomen, surrounded by thick enhancing saclike structure. Evidence of fluid collection between bowel loops is seen.

 

An exploratory laparotomy was performed through a midline incision. On opening the abdomen, the small bowel from the duodenojejunal flexure to the ileocecal junction was found to be enclosed in a sac made up of two layers. The mass contained approximately 300 mL of serosanguineous fluid. The outer membrane of the sac was tough and fibrous, whereas the internal membrane was thin and avascular. Minimal adhesions were seen between the intestinal loops themselves. When the membranes were separated, three strictures were found—the first, approximately 75 cm from the duodenojejunal flexure and the other two, within 30 cm of the ileocecal junction. The entire small intestinal tract was separated from the membrane layers, which were excised and sent for histologic examination.

When cultured, the fluid from the abdominal sac did not grow acid-fast bacilli. The resected segment showed a thickened membranelike structure on the serosa throughout the length of the resected small intestine. The cut section showed two ileal strictures, one 5.4 cm and the other 1.8 cm proximal to the ileocecal junction. A few mucosal ulcers were seen in the ileum. At gross examination, the cecum, appendix, and ascending colon appeared normal. Five lymph nodes, the largest measuring nearly 1 cm in diameter, were seen in the mesentery. Sections from the site of stricture and the ulcers showed ulcerated mucosa covered with moderately dense inflammatory exudates composed of lymphocytes, neutrophils, and eosinophils. No evidence of granuloma or healed tuberculosis was seen. The resected lymph nodes also showed reactive hyperplasia with no evidence of tuberculosis.

The patient had an uneventful recovery from the surgery. He was given antituberculous drugs empirically. Six months after surgery, he remains asymptomatic.


Discussion
Top
Introduction
Case Report
Discussion
References
 
Abdominal cocoon is a synonym for sclerosing encapsulating peritonitis. It is a relatively rare cause of intestinal obstruction and is found predominantly in adolescent girls. It is characterized by a thick fibrotic membrane that encases the bowel, forming a sac or cocoon along with some internal adhesions. At times, the surrounding membrane may be thin and difficult to identify on a CT scan, making it difficult to diagnose this condition preoperatively on imaging [2]. Since the time this disease was first described, approximately 35 cases have been reported [1].

The exact cause of abdominal cocoon is uncertain. A history of prior abdominal surgery or the presence of a complicated abdominal-wall hernia or active biliary tract inflammation has been found in some patients and thought to have caused peritoneal injuries or inflammation [3]. However, in some patients, no underlying cause may be found. The underlying causes of other conditions with pathologic findings similar to those seen in abdominal cocoon have been investigated. In a study of 554 patients with cirrhosis, 69 had peritoneovenous shunts, and at autopsy, 38% of these patients were found to have generalized peritoneal fibrosis, with cocoon formation [3]. Because these patients had faster ascitic fluid circulation, it was hypothesized that increased deposition of fibrin on the peritoneum, after the release of fibrogenic cytokines, converted fibrinous adhesions to generalized peritoneal fibrosis. This description is similar to the findings seen in our patient. However, the basic cause of abdominal cocoon formation in the setting of cirrhosis with peritoneovenous shunts appears to be different from that in our patient. A rare case of abdominal cocoon also has been reported in a patient with a liver transplant [4]. Tuberculous infection causing similar findings also has been documented and described in some cases [5]. However, it should be noted that more commonly, tuberculosis of the abdomen produces dense and thick fibrotic adhesions, unlike those seen in this case. In our patient, one may presume that his history of surgery for intestinal perforation was probably the cause of fibrinous adhesions and peritoneal fibrosis. However, this is just an assumption.

The preoperative diagnosis of this entity may be helpful for proper treatment of these patients. A simple surgical release of the entrapped bowel via removal of the fibrotic membrane is all that is necessary to free the bowel if no other cause of obstruction, such as a stricture, is found, as was the case in our patient.

Currently, abdominal CT scans are requested commonly by clinicians, and the radiologist must be aware of this entity to make an appropriate CT diagnosis. Compared with other imaging techniques, CT gives a more complete picture of this entity as well as any associated complications, if any, and may also help to exclude other causes of intestinal obstruction.

Conventional radiographs may show evidence of small-bowel obstruction, with dilated bowel loops and air–fluid levels in abdominal radiographs obtained with the patient standing. A barium meal and follow-through study also may help sometimes in revealing this condition by showing a conglomeration of multiple bowel loops that appear to adhere to each other with a suspected saclike structure surrounding them. However, the exact diagnosis can be made only by identifying the fibrous membrane surrounding the bowel loops, a condition that is best visualized on a CT scan, which gives more accurate information on the degree of obstruction and the types of bowel loops involved.

Radiologists should be aware of this relatively rare cause of intestinal obstruction and its imaging findings because a CT scan most often can clinch the diagnosis and is therefore helpful in the treatment of these patients.


References
Top
Introduction
Case Report
Discussion
References
 

  1. Hamaloglu E, Altun H, Ozdemir A, Ozenc A. The abdominal cocoon: a case report. Dig Surg2002; 19:422 –424[Medline]
  2. 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[Medline]
  3. Stanley MM, Reyes CV, Greenly HB, Nemchausky B, Reinhardt F. Peritoneal fibrosis in cirrhotics treated with peritoneovenous shunting for ascites: an autopsy study with clinical correlation. Dig Dis Sci 1996;41:571 –577[Medline]
  4. Abdul S, Al-Oazweni H, Zalat S, Al-Sumait B, Asfar S. Cocoon abdomen in a liver transplant patient. J R Coll Surg Edinb 2002;47:579 –581[Medline]
  5. Lalloo S, Krishna D, Maharajh J. Case report: abdominal cocoon associated with tuberculous pelvic inflammatory disease. Br J Radiol 2002;75:174 –176[Abstract/Free Full Text]

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