ANSWER: (A) Down syndromeREF: Sabiston 18th ed chapter 71Duodenal atresia (DA) is thought to occur as a result of failure of vacuolization of the duodenum from its solid cord stage. The range of anatomic variants includes duodenal stenosis, mucosal web writh intact muscular wTall (so-called windsock deformity); two ends separated by a fibrous cord, or complete separation writh a gap within the duodenum.Associated Anomalies: DA is associated with several conditions, including prematurity, Down syndrome, maternal polyhydramnios, malrotation, annular pancreas, and biliary atresia. Other anomalies, such as cardiac, renal, esophageal, and anorectal anomalies, are also common. In most cases, the duodenal obstruction is distal to the ampulla of Vater, and infants present writh bilious emesis in the neonatal period. In patients with a mucosal wreb, the symptoms of postprandial emesis may occur later in life.Diagnosis: The classic plain abdominal radiograph of DA is termed the double-bubble sign (air-filled stomach and duodenal bulb, In cases in which there is no distal air, the diagnosis is secured, and no further studies are necessary. On the other hand, if distal air is present, an upper gastrointestinal contrast study is performed fairly rapidly. This study is important not only to confirm the diagnosis of duodenal stenosis or atresia but also to exclude midgut volvulus, which wrould constitute a surgical emergency.Treatment: The management of DA is by surgical bypass of the duodenal obstruction as either a side-to-side or proximal transverse-to-distal longitudinal (diamond-shaped) duodenoduodenostomy.