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

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... ed 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 contrastmedium study was obtained (Figure) .