A rare case of pelviureteric junction obstruction in the uncrossed kidney of a crossed fused renal ectopia.

Crossed renal ectopia with fusion is an extremely rare congenital anomaly with few reported cases of pelviureteric junction obstruction, which often involves the crossed-over kidney. To our knowledge, we describe the second case in literature to report an uncrossed kidney with pelviureteric junction obstruction and giant hydronephrosis, which obstructs the pelviureteric junction of the crossed-over kidney. The grossly hydronephrotic kidney was found to be poorly functioning and an aberrant crossing vessel was considered to be potentially involved, raising both diagnostic and management challenges. By reporting this case, we aim to stress the importance of adequate mapping collecting systems, drainage patterns and vascular supply in such crossed fused anomalies.