Fact-sheet: Bowel malrotation
Updated on 10/01/2018 at 10:06 AM
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Definition
= congenital anomalies of the intestine due to a rotation defect of the primitive intestinal loop during embryonic development
The embryological rotation of the primitive midgut loop schematically occurs in 3 stages = 3 successive 90° rotations of the primitive intestinal loop, centered on the superior mesenteric artery, in a counterclockwise direction.
2 types:
- complete common mesentery: rotation arrest after a first 90° rotation --> no risk of mesenteric volvulus (because the mesenteric root is long).
- incomplete common mesentery: rotation arrest after two 90° rotations (overall 180° rotation) --> risk of mesenteric volvulus (because the mesenteric root is short)
Clinical features
- Complete common mesentery: asymptomatic, incidental finding.
- Incomplete common mesentery: mesenteric volvulus = most common cause of neonatal obstruction (1/500 births)
Clinical presentation: distended abdomen and early bilious vomiting.
ANY GREEN VOMITING IN A NEWBORN IS MESENTERIC VOLVULUS UNTIL PROVEN OTHERWISE.
Radiography
Plain abdominal radiograph: abnormal distribution of bowel gas.
- complete common mesentery: colonic gas on the left with a left paramedian cecum and small bowel gas on the right
- incomplete common mesentery: empty right iliac fossa with cecum in a high midline or subhepatic position
Duodenal frame: abnormal position of the duodenojejunal angle (ligament of Treitz)
- to the right of or anterior to the spine (normally projects to the left of the spine)
- located inferior to the superior genu
- poorly marked
Ultrasound
Analysis of mesenteric vessel position:
- normally: the superior mesenteric vein lies to the right of the superior mesenteric artery.
- malrotation: reversal of mesenteric vessel position (vein to the left of the artery)
CT
- complete common mesentery: colonic frame on the left with a left paramedian cecum and small bowel on the right
Reversal of mesenteric vessel position
- incomplete common mesentery: empty right iliac fossa with cecum in a high midline or subhepatic position.
Reversal of mesenteric vessel position
Management
Preventive surgery should be discussed for incomplete common mesentery given the risk of volvulus (Ladd procedure): stretching of the mesenteric root and repositioning of the digestive tract into a complete common mesentery configuration.
Differential diagnosis
In the setting of high neonatal obstruction: consider duodenal atresia and jejunal atresia.