A 13-year-old girl presented with a 2-week history of sharp, intermittent, periumbilical abdominal pain. The pain does not radiate; activity worsens the pain, whereas rest alleviates it. The pain is neither worsened by eating nor relieved by defecation. She reports approximately 6 episodes of nonbloody and nonbilious vomiting during these 2 weeks. She reports normal daily bowel movements. There has been no change in the frequency or volume of her stools since the onset of abdominal pain, but she has had occasional loose stools. She denies hematochezia and constipation, but says that occasionally she will feel the need to defecate but cannot. She has had a 3.15-kg (7-lb) weight loss in the past 3 months. She also describes recent onset of malaise and chills. She denies any rash, joint pain, or fever.