Iliacus abscess.

Iliacus muscle abscess originating from the sacroiliac joint was diagnosed prior to operation in a 13-year-old boy with the assistance of technetium-99m bone imaging and computerized tomography. Preoperative identification of the iliacus abscess enabled the surgeon to select an anterior (apophyseal splitting) retroperitoneal approach, which permitted drainage of both the ilium and the iliacus muscle.