A 2-hour-old male infant had been diagnosed in utero with polyhydramnios. Now he is vomiting stomach contents and bile. The vomiting continues for 2 days. Radiographic examination reveals a "double bubble" sign on ultrasound scan. The child cries consistently and is constantly hungry but has lost 300 g in weight. Which of the following conditions will most likely explain the symptoms?

Duodenal atresia is the result of a failed reformation of the lumen of the duodenum and is associated with vomiting within the first few days of birth. Polyhydramnios is seen due to abnormal absorption of amniotic fluid by the intestines. Finally, radiographic or ultrasound examination would review the "double bubble" sign because of distended, gas-filled stomach. Duodenal stenosis is caused by incomplete recanalization of the duodenum and often results in vomiting of stomach contents plus bile later in life. Hypertrophied pyloric sphincter would cause projectile vomiting. An atrophied gastric antrum is caused by the removal of the membranous lining of the stomach and occurs proximal to the site of the entrance of the common bile duct; therefore, vomit would not contain bile. Tracheoesophageal fistula is an abnormal passage between the trachea and esophagus and would not be a cause for any of symptoms cited in the question.