Retroperitoneal neurogenous choristoma.

A 6-year-old girl with urinary complaints underwent ultrasonography, which revealed a retroperitoneal cystic mass adjacent to the left kidney. Computerized tomography did not demonstrate whether the mass was an adrenal cyst or a duplicated upper pole segment. Exploration revealed a neurogenous choristoma, which is a collection of histologically normal tissue that is ectopically situated. We believe that this is the first report of this rare entity occurring in the retroperitoneum.