Radiological Case of the Month

5-MONTH-OLD male infant was admitted to the hospital with a 3-day history of fever associated with anorexia, fussiness, and decreased sleep. Information from a review of systems and history of present illness revealed a several-week history of constipation and gastroesophageal reflux. On physical examination the infant appeared healthy and had a nontender, firm, abdominal mass palpated in the right upper quadrant. The mass extended 9 cm below the costal margin. By auscultation, bowel sounds were present, and a diffuse low-pitched bruit was heard over the mass. Findings from the remainder of the physical examination were unremarkable. Results of serum chemistry, liver function tests, prothrombin time, and partial thromboplastin time were nor