Congenital Diseases in the Newborn 5.3.1

Duodenal Obstruction

Duodenal obstruction is the most common cause of proximal (high) intestinal obstruction in new-borns. It can be complete (atresia) or incomplete (stenosis). Atresia is caused by failure of recannula-tion. Approximately 30% of patients with duodenal atresia have Down syndrome. Duodenal stenosis can be the consequence of internal or external causes that impede re-canalization such as malrotation with or without volvulus, a duodenal web, pancreas annulare and duplication cysts (Carty et al. 2005; Parker 2003; Grier 1999; Devos and Meradji 2003; Berrocal et al. 1999). Prenatal diagnosis of a 'double bubble' with polyhydramnios in 40% of cases is more common today. Clinical manifestations are persistent (bilious) vomiting from the first hours of life, possibly complicated by dehydration. The abdomen is flat, scaphoid or minimally distended.

A conventional abdominal (plain) film in two directions (including a horizontal beam) may show a (markedly) dilated stomach and the proximal part of the duodenum.

Most important in these cases is to exclude conditions that are life-threatening for the patient. As intestinal malrotations may lead to bowel ischemia, which may subsequently lead to bowel necrosis, the patient's life is at risk when less than 3 in. of small bowel remain (Andrassy and Mahour 1981).

In the case of atresia, there will be no air in other parts of the intestinal tract, the so-called 'double bubble' sign (Fig. 5.3). No other imaging modality is then needed. However, the 'double bubble' sign may be absent if the patient has vomited, has a feeding tube or if there is intermittent passage of air.

In the case of duodenal obstruction with similar clinical signs as atresia, but with air distal to the duodenum, intestinal malrotation should be ruled out.

The sign of an intestinal malrotation is sometimes recognizable on an abdominal plain film in which the small bowel will be located in the right upper abdomen. When this is observed, color Dop-pler sonography shows in 85% of the cases an abnormal position and course of the superior mesenteric artery with dextroposition to the superior mesen-

teric vein and the small bowel will lie in the right instead of the left upper quadrant (Figs. 5.4 and 5.5) (Carty et al. 2005; Parker 2003; Grier 1999; Devos and Meradji 2003; Berrooal et al. 1999).

An upper GI tract examination (with low osmo-lar water soluble contrast medium) is the optimal study to verify whether normal bowel rotation has occurred, and the imaging hallmark for this is to identify the position of the duodenojejunal junction (ligament of Treitz) (Fig. 5.6a). Radiographi-cally this implies, with an anteroposterior supine positioning of the patient, that the duodenojejunal junction is to the left of the vertebral column and at the same level or more superior than the duodenal

Fig. 5.4. An infant with intestinal malrotation on US. Abnormal position of the superior mesenteric arteria dextropositioned to the mesenteric vein

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