Internal hernia causing closed loop small bowel obstruction

Case contributed by Vikas Shah


Roux-en-Y gastric bypass for weight loss one year earlier. 2 days of abdominal pain and vomiting.

Patient Data

Age: 45 years
Gender: Female

The AP scout image shows distended bowel within the left upper quadrant.

Fluid distension of the biliopancreatic limb (stomach, duodenum, and jejunum), with two separate transition points in the left upper quadrant seen as abrupt narrowing of the small bowel with a twisting configuration of the adjacent mesentery. The transition points are proximal to the distal jejunojejunal anastomosis and the alimentary limb is not dilated. No free fluid or free air.

The appearances are consistent with a closed-loop configuration of small bowel obstruction, with the most likely etiology being an internal hernia and associated volvulus, with additional consequent obstruction of the upstream stomach, duodenum and jejunum.

Dilatation of the common bile duct is also noted. 

Case Discussion

At surgery, the small bowel was confirmed to be obstructed but viable, and an internal hernia was reduced and the mesenteric defect closed.

Internal hernias can be difficult to diagnose on CT imaging because the actual anatomic defect is not seen, but rather inferred from the appearances of the small bowel and mesentery. Clustering of a segment of bowel, an abrupt change in caliber, and swirling or twisting of the bowel and/or its mesentery are all helpful features to look for. Volvulus may co-exist with an internal hernia. Patients who have had a Roux-en-Y gastric bypass are at risk of internal hernias due to mesenteric defects created during the surgery to form anastomoses.

The CBD dilatation was not present on subsequent imaging, and was inferred to be due to the duodenal obstruction.

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