Ectopic nephrogenic rest in the inguinal canal in a 6-month-old girl and a review of published studies.

Ectopic nephrogenic rests in the inguinal canal are rare. Usually discovered incidentally during surgery, these rests should raise the suspicion of an early extrarenal Wilms tumor. The differential diagnosis between the two entities is not only difficult but also essential, since they imply different treatment decisions. We report a rare case of an inguinal ectopic nephrogenic rest found in a 6-month-old girl and discuss the clinicopathological implications of this condition. The patient was admitted for a routine repair of a presumed inguinal hernia; during surgery, a nodular mass was noted in the inguinal canal. Pathological diagnosis confirmed the diagnosis of an extrarenal hyperplastic nephrogenic rest. Five previous cases of ectopic nephrogenic rests originating in the inguinal canal have been reported, all of which were associated with a patent processus vaginalis. In this case, the nephrogenic rest was not associated with a congenital inguinal hernia.