At the time of delivery, a woman is noted to have a large volume of amniotic fluid. At 6 hours of age, her baby begins regurgitating small amounts of mucus and bile-stained fluid. Physical examination of the infant is normal, and an abdominal x-ray is obtained (see below). Which of the following is the most likely diagnosis of this infant's disorder?
Gastric duplication Pyloric stenosis Esophageal atresia Duodenal atresia