A 14-YEAR-OLD African American adolescent girl presented with a 6-month history of intermittent upper abdominal pain and postprandial vomiting. These symptoms had become progressively worse during the 2 months prior to hospital admission. The medical history was unremarkable except for dysmenorrhea. The physical examination revealed a thin adolescent girl with a weight of 35 kg (10th percentile) and height of 150 cm (25th percentile). Her vital signs were normal. The abdomen was slightly distended with mild tenderness in the epigastric region and normal bowel sounds on auscultation. No hepatosplenomegaly or ascites was detected. Results of a complete blood cell count and erythrocyte sedimentation rate were normal. A guaiac test of the stool was negative for occult blood. A radiograph of the abdomen revealed gastric distention. Abdominal and pelvic ultrasound was normal. An upper gastrointestinal tract contrast-medium study was obtained (Figure 1).