A 15-YEAR-OLD girl presented with a 2-hour history of severe abdominal pain. The pain was located in the left lower quadrant and was not initially associated with nausea and vomiting. It was neither relieved nor aggravated with movement. She reported similar pain several months earlier, with rapid spontaneous resolution. That episode was considered to be related to a renal stone, but no further testing was performed because she was symptom free at the time of the office visit. She had no history of urinary symptoms.