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THE PAEDIATRIC ABDOMEN 237
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 (Fig. 9.16). 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. 33 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’ 34 (Fig. 9.16). 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.
TS
A
B
Figure 9.16 Volvulus. (A) Mesentery and superior mesenteric vein are twisted around the superior mesenteric artery,
which is seen in cross-section at the centre of the film. (B) Barium meal shows corkscrewing of the duodenum away
from the midline, consistent with a malrotation and volvulus. (By kind permission of Dr Delia Martinez, Leeds.)