Transplanting horseshoe kidneys: a worldwide survey.

PURPOSE: Horseshoe kidney is the most common anatomical renal variation. It represents a fusion anomaly, usually of the lower poles. Horseshoe kidneys can be transplanted en bloc or after division of the renal isthmus. We constructed a decision cascade for horseshoe kidney transplantation.

MATERIALS AND METHODS: A worldwide survey of transplantation clinics and foundations was performed to discover cases of horseshoe kidney transplantation. In each case data were collected on horseshoe kidney anatomy and post-transplantation results. The number of renal arteries and veins was correlated with primary nonfunction due to technical failure.

RESULTS: From 1975 to 2000, 23 horseshoe kidneys were transplanted en bloc, while 57 were split and transplanted into 97 recipients. Primary nonfunction was observed in 4.3% and 13.4% of en bloc and divided transplanted kidneys, respectively. Postoperatively a urinary fistula formed after renal isthmus division in 2 cases. An increased number of renal vessels was not associated with an increased risk of primary nonfunction.

CONCLUSIONS: Horseshoe kidney anatomy should be closely inspected after explantation. The decision to split a horseshoe kidney should be based on urinary collecting system anatomy in the renal isthmus and on the number as well as the position of the renal vessels. Horseshoe kidneys can and should always be considered for transplantation.