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MIDGUT VOLVULUS MALROTATION
Category: Diagnostic Radiology
Abstract : Midgut volvulus Malrotation of the midgut occurs as a result of failure of
normal rotation of the small bowel during intrauterine development, resulting in
a shortened mesenteric fixation of the small bowel to the posterior abdominal
wall. This predisposes the small bowel to twisting (volving) around the
mesenteric vascular axis, resulting in bowel obstruction and vascular compromise
Midgut volvulus
Malrotation of the midgut occurs as a result of failure of
normal rotation of the small bowel during intrauterine development, resulting in
a shortened mesenteric fixation of the small bowel to the posterior abdominal
wall.
This predisposes the small bowel to twisting (volving) around the
mesenteric vascular axis, resulting in bowel obstruction and vascular compromise
with a risk of infarction of most of the small bowel if the volvulus is not
treated quickly. Following volvulus the child presents with acute pain and
bile-stained vomiting. The bowel may intermittently twist and untwist, resulting
in temporary alleviation of symptoms, which may make diagnosis more
difficult.
The definitive diagnosis is usually made fluoroscopically
during an upper gastrointestinal contrast study. In malrotation the duodenal
jejunal flexure is generally found to be lower and in a more medial position
than is normal and if a volvulus has occurred a corkscrew appearance of the
volved small bowel may be seen. The proximal duodenum will be dilated secondary
to the duodenal obstruction.
Malrotation without volvulus may be
suspected during a sonographic examination performed for intermittent abdominal
pain due to the associated malposition of the mesenteric vessels and is best
seen on colour Doppler sonography. The normal relationship of the superior
mesenteric vein to the superior mesenteric artery is reversed, with the superior
mesenteric vein lying anteriorly and/or to the left of the superior mesenteric
artery. However this finding is not always present and may occasionally be seen
in normal individuals and therefore a contrast study is required for
confirmation.
When volvulus has occurred the vessels may be noted to be
spiralling around a bowel mass, that is, the ‘whirlpool sign’. Other ultrasound
appearances include a dilated, fluid-filled obstructed duodenum, although the
obstructed duodenum may be gas-filled, obscuring visualization. This sign is not
invariable, however, and a contrast study may still be needed to confirm or
exclude the diagnosis of a midgut volvulus. Surgery is performed to untwist the
bowel, which is then laid carefully in the correct position; attachment is
usually unnecessary, as abdominal adhesions tend to stabilize the bowel.
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