We report here on a case of avulsion of the ureteropelvic junction in a 7-year-old boy who was injured in a car accident. Severe brain trauma took precedence over signs and symptoms of blunt abdominal trauma, but 24 hours after the accident, progressive distension of the abdomen required further evaluation. Ultrasound examination and a computed tomography scan revealed disruption of the ureteropelvic junction. Simple primary anastomosis was performed. We discuss the characteristics of this unusual injury and include a review of the literature.