Figure 1. Classification of duplex kidney anatomy.
Compared with a normal kidney ( a), complete duplication produces a duplex kidney with two poles that drain into two ureters ( b). Incomplete duplication leads to a Y-shaped ureter ( c). Blind ureters do not drain into the bladder ( d). In the rare case of inverted Y-ureteral duplication, two ureters fuse before entering the kidney ( e).