Small bowel mesentery internal hernias (alternative plural: herniae) are a form of internal bowel herniation involving protrusions of viscera through defects in the peritoneum or bowel mesentery.
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Epidemiology
This type of internal herniation is more often seen in neonates than in adults ref.
Clinical presentation
The most common presentation is with small bowel obstruction. Sometimes, they can have mostly silent symptoms of nausea and epigastric discomfort only ref.
Complications
small bowel obstruction
volvulus
strangulation
bowel ischemia
bowel perforation
Pathology
Congenital peritoneal or mesenteric defects are usually present in the pediatric population. Defects are more common in the region of the ligament of Treitz or the ileocecal valve ref.
In adults, transmesenteric hernias may be congenital but may also result from mesenteric defects caused by trauma, inflammation, or surgery ref.
Location
There are two types ref:
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transmesenteric small bowel internal hernia
much more common
occurs through a defect in the mesentery
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intramesenteric (mesenteric pouch hernia)
occurs in the mesentery through a mesenteric defect
predominantly in pediatric patients
Radiographic features
CT
Small bowel internal mesenteric hernias manifest as proximal small bowel dilatation and an abrupt change in caliber at the level of the mesenteric defect. Mesenterial stranding sign is often associated. The mesenteric vascular pedicle can be engorged or stretched ref.
Transmesenteric small bowel internal hernias do not typically show a "sac-like" cluster of vessels (like a paraduodenal internal hernia), and differentiation between a transmesenteric internal hernia and a small bowel obstruction from other causes can sometimes be difficult ref.
Intramesenteric small bowel internal hernias may appear "sac-like", with anterior and superior displacement of the superior mesenteric artery ref.
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