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Transmesenteric internal hernia

Case contributed by Nolan Walker
Diagnosis almost certain

Presentation

Longstanding right sided abdominal pain. Outpatient. No previous surgery.

Patient Data

Age: 65 years
Gender: Female

There is a transmesenteric internal hernia.

The ascending colon and cecum have herniated through a transmesenteric defect into the left iliac fossa.

The hernial orifice is situated immediately anterior to the aortic bifurcation.
The cecum is displacing the fourth part of the duodenum superiorly.

The small bowel is situated anterior to the cecum, in the left iliac fossa.

There is no fluid within the hernial sac to suggest incarceration or strangulation and there is no small or large bowel dilatation.

The SMV is enhancing normally.

Annotated image

The transverse colon and terminal ileum are seen to pass through the mesenteric defect at this point (red circle).

The small bowel (green line) is situated externally to the large bowel (red line) in the abdomen. This is a very useful sign. 

Case Discussion

This is a case of a transmesenteric internal hernia. There is no history of previous surgery to account for the mesenteric defect. There is no malrotation.

There is no strangulation at present. Signs of strangulation include bowel wall thickening inside the hernial sac, lack of SMV enhancement, fluid in the hernial sac and fat stranding in the herniated bowel mesentery.

Internal hernias can be overlooked if the large bowel is not traced carefully.

A useful sign to alert the radiologist to a possible internal hernia is seeing the cecum abnormally positioned, with the additional clue of seeing the small bowel surrounding the outside the large bowel (as illustrated).\

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