Peritoneal encapsulation: presenting as small bowel obstruction in an elderly woman.

Editor,

Small bowel obstruction is one of the common surgical emergencies. It is most often due to adhesions following previous operations or obstructed hernias. Peritoneal encapsulation is one of the very rare causes of intestinal obstruction, often diagnosed at laparotomy. This condition is largely asymptomatic and found incidentally at laparotomy or autopsy. Only a few cases have been reported in the literature and presentation as bowel obstruction is extremely rare. We report a case of peritoneal encapsulation presenting as a small bowel obstruction following herniation of the bowel loop through the sac in an elderly woman. Awareness of this condition will facilitate proper management.

Case report

An 82 yr old woman presented with three days history of lower abdominal pain, progressive abdominal distension and vomiting. She was previously investigated with barium enema for intermittent lower abdominal pain, which showed diverticular disease involving the sigmoid colon. There was no previous history of open abdominal operation, peritonitis or prolonged use of beta-blockers. Physical examination showed asymmetrical abdominal distension involving mainly right lower and mid abdomen. There was mild tenderness in the right iliac fossa with palpable bowel loops, and a reducible right femoral hernia. Abdominal X-ray showed a few dilated small bowel loops in the lower abdomen (fig 1). Inflammatory markers were mildly raised, otherwise blood investigations were unremarkable.

Preoperative abdominal X-ray showing dilated small bowel loops

A provisional diagnosis of partial obstruction was made. She was treated conservatively overnight but symptoms gradually worsened. An obstructed femoral hernia was suspected and an emergency laparotomy performed. There was a shiny white peritoneal layer behind the peritoneum and bowel from the duodeno-jejunal flexure to the ileocaecal junction was found to be encased in a sac. A loop of terminal ileum was herniated through the sac with a tight constriction. The sac was excised with the release of the intestinal loop. Peritonitis developed post-operatively and at repeat laparotomy, small bowel loops were grossly distended throughout their length and were densely matted and adherent to the ischaemic terminal ileum loop and mesentery. A long segment of ileal loop was resected and a jejuno-colic anastomosis established, and a duodenal tear repaired. Postoperatively she developed pulmonary oedema, hypoproteinaemia, and hypoalbuminaemia and died from a chest infection. A post-mortem was not performed. Histology of the sac was not available but the morphological features were consistent with peritoneal encapsulation.

Discussion

Peritoneal encapsulation is a rare developmental abnormality in which part or the entire small bowel is encased in an accessory sac derived from the yolk sac. This is attached to the ascending and descending colon laterally, the transverse mesocolon superiorly and merges with posterior parietal peritoneum inferiorly. The membrane has two openings, one around the duodenal-jejunal flexure and the other at the ileocaecal junction. Greater omentum covers the sac but is not attached to it. It was first described by Cleland in 1868. Less than 20 cases have been reported and the diagnosis was made incidentally in most of these1. The condition is largely asymptomatic, but some cases have presented as bowel obstruction1.

Diagnosis may be impossible preoperatively. Naraynsingh2 described two clinical signs, which help in diagnosis; a fixed, asymmetrical distension of the abdomen, which does not vary with peristaltic activity and a difference in the consistency of the abdominal wall to palpation. Both these findings can also be present in abdominal cocoon (Idiopathic sclerosing encapsulating peritonitis - SEP). Plain radiography in peritoneal encapsulation is usually normal or can show features of obstruction. Computed tomography may visualise the membrane. The membrane is not adhered to the inner bowel loops. When encountered during the exploration for bowel obstruction, it can be removed and excised easily.

Peritoneal encapsulation, Idiopathic SEP (abdominal cocoon) and SEP of known cause are different rare pathological conditions. Cases have been reported with features of abdominal cocoon as peritoneal encapsulation.3 Tsunoda4 described a case of idiopathic SEP combined with peritoneal encapsulation proposing a congenital theory for abdominal cocoon; a chronic inflammatory process of “developmental peritoneal encapsulation” which looks like a cocoon. The consistent siting of the lesion with invariable involvement of the ileocaecal junction also supports the idea of developmental abnormality in abdominal cocoon5.

Foo6 reported 10 cases of small bowel obstruction in young girls who had an obstruction due to a membrane covering the small intestine, which they described as “Abdominal Cocoon”. The fibrous membrane showed signs of chronic inflammation and it was postulated that the condition is due to the retrograde menstruation with sub clinical viral primary peritonitis, resulting in the development of an encapsulating membrane on the intestine. Since then it has been described in all age groups and genders. It is not restricted to the tropics or subtropics.

Abdominal cocoon (Idiopathic SEP) is thought to be an acquired condition of unknown aetiology. It usually presents as bowel obstruction either by extra luminal compression by a constricting band or by torsion of the bowel. Development of sclerosing encapsulating peritonitis has also been reported from various known causes. Cases of small bowel obstruction due to sclerosing encapsulating peritonitis in patients on long-term proctolol have been described as early as 1974.7,8 It was a well recognized complication of proctolol and it is no longer in use. Other common causes include peritoneal dialysis and peritoneo-venous shunting. It is reported rarely in patients with tuberculosis, sarcoidosis, familial Mediterranean fever, gastro intestinal malignancy, protein-S deficiency, after liver transplantation, fibrogenic foreign material and latinised thecomas.

Various imaging findings have been described for abdominal cocoon, including delayed bowel transit, peritoneal and bowel calcification, bowel wall thickness, loculated ascites and circumscribed mass of bowel loops conglomerated in one area9 (cauliflower sign). A thick fibrinous membrane surrounding the bowel loops can be visualised by CT scan while it also gives information on the degree of obstruction and the types of bowel loops involved10. In peritoneal encapsulation the membrane is free from underlying bowel loops and the histology of the sac is predominantly mesothelial with or without chronic inflammation or fibrosis1. A thick fibrocollaginous membrane encasing the bowel loops along with some internal adhesions characterises the sac in the abdominal cocoon. At times it may be difficult to peel it off or excise it without perforating the bowel.

The diagnosis is intra-operative in majority of cases and excision of the sac with enterolysis is all that is required. Bowel resection may be necessary if the membrane cannot be stripped atraumatically or with obvious gangrene of the bowel. Recently there have been reports of SEP secondary to chronic peritoneal dialysis treated successfully with immunosuppressive therapy and tamoxifen9. Both peritoneal encapsulation and idiopathic SEP are rarely documented and poorly understood surgical problems. A better awareness of these conditions will facilitate the proper management if encountered as an emergency. Distinction between these two entities is still not clear and needs further study.