Petersen internal hernia resulting in volvulus of the entire small bowel

Case contributed by Michael P Hartung
Diagnosis certain

Presentation

Abdominal pain following hip surgery.

Patient Data

Age: 60 years
Gender: Female

Changes of gastric bypass. Small bowel is diffusely abnormal with mesenteric edema and thickening of the loops. Bowel configuration is abnormal with swirling/clustering of the bowel. There is severe narrowing of the central SMV as it swirls around midline, as well as several areas of abnormal angulation and narrowing of central and distal branches (best appreciated on coronal).

Case Discussion

An unexpected case of internal hernia following orthopedic surgery resulting in herniation and volvulus of the entirety of the small bowel through a Petersen defect, accounting for this diffusely abnormal appearance. As bowel becomes entrapped in an internal hernia, it can become edematous, dilate, and twist around the points of fixation (entering/exiting the hernia), resulting in both internal hernia and volvulus, as in this case.

Following the mesenteric vessels is key to raising concern of internal hernia, and importantly being aware that gastric bypass patients are a special subgroup at risk for developing internal hernia due to the mesenteric defects created during JJ anastomosis. Specifically following the SMV is key, as centrally it becomes severely narrowed and slit-like as it swirls around the SMA (see annotated images). The distal branches continue to swirl with multiple areas of angulation and venous narrowing (best appreciated on coronal images), supporting the diagnosis of volvulus.

It is essential to think broadly about your differential for these patients and not settle on "nonspecific enteritis" when encountering small bowel thickening or edema, and consider that vascular compression in the setting of internal hernia can contribute to an edematous, inflammatory appearance. Regarding terminology, this can be considered in the spectrum of closed-loop physiology due to internal hernia and volvulus, but is not simply as a "closed loop obstruction". The diagnosis of an internal hernia was confirmed at the time of surgical repair.

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