Diagnostic ultrasound ( PDFDrive )

1842 PART V Pediatric Sonography
FIG. 53.16 Normal Small Bowel. High-frequency ultrasound images show the thin, distinct layers of normal bowel loops.
these indings are valuable for suggesting the diagnosis, absence
of these indings does not exclude malrotation or volvulus. 48
A inal cause of distal duodenal obstruction is a duodenal
diaphragm that has stretched into a windsock coniguration
(Fig. 53.21). he distal end of the obstructed duodenum will
have a rounded shape in this condition, 49 as opposed to the
tapered end, which is seen more oten with midgut volvulus.
FIG. 53.17 Duodenal Atresia. The presence of grossly distended
duodenal bulb (D) and stomach (S) constitutes the sonographic “double
bubble” sign.
vigorous peristalsis of the dilated, obstructed duodenal C-loop
is seen (Fig. 53.18) and characteristic tapering of the distal, twisted
end can be visualized. 42 Color Doppler will show the “whirlpool”
sign of twisted mesenteric veins around the superior mesenteric
artery (SMA) (Fig. 53.19). Obstruction from peritoneal (Ladd)
bands, which also accompanies rotational anomalies of the
intestine, can have a similar appearance. In addition to these
indings, an abnormal position of the superior mesenteric vein
(SMV) and artery can be seen in patients with intestinal malrotation,
with or without volvulus (Fig. 53.20). Failure of normal
embryologic bowel rotation leaves the SMV anterior to or to the
let of the SMA 43,44 as opposed to its normal position to the right
of the artery. Although this inding is not always present in
volvulus, 45 it is probably worthwhile to observe the relationship
of these vessels in any child who is undergoing sonography for
the evaluation of vomiting. In addition, documentation of the
normal position of the third portion of the duodenum posterior
to the SMA and anterior to the aorta can be used to exclude
malrotated bowel. With practice, this becomes easier. 46,47 Although
Duodenal Hematoma
Duodenal hematoma is a common complication of blunt
abdominal trauma in children, including those with battered
child syndrome. Sonography can demonstrate the dilated,
obstructed duodenum and more speciically can show evidence
of an intramural hematoma 50-52 (Fig. 53.22). he intramural
hemorrhage initially causes echogenic thickening of the wall of
the duodenum, but as time passes, the hematoma undergoes
liquefaction and the thickened wall becomes hypoechoic. Similar
hematomas can occur with Henoch-Schönlein purpura. 53
Small Bowel Obstruction
he diagnosis of small bowel obstruction is usually accomplished
with plain radiographs. At times, however, ultrasound can be
used to help determine the site or cause of the obstruction. In
cases of mechanical small bowel obstruction, the luid-illed,
dilated, hyperperistaltic loops of small bowel proximal to the
obstruction are usually clearly visible with ultrasound (Fig. 53.23).
One can also assess small bowel in both lower quadrants in an
attempt to ascertain the level of obstruction and also try to
determine the cause of obstruction if lesions such as duplication
cysts, small bowel intussusception, or even interloop collections
from a perforated appendix are present.
In neonates with congenital causes of small bowel obstruction
(e.g., ileal atresia, meconium ileus), prenatal intestinal perforation
can occur, releasing variable amounts of meconium into the
peritoneal cavity. In some of these fetuses, the perforation heals
in utero, and the only clues that remain ater birth are scattered