ABSTRACT
Duplication of the upper urinary tract is the most common urinary tract anomaly, occurring in approximately one in 125 individuals at post-mortem. There is a female preponderance (70 per cent) and a familial tendency (11 per cent of first-degree relatives also have a duplication), and in 20 per cent of patients it is bilateral. Duplex kidneys have two separate poles or moieties (upper and lower), each with a separate collecting system. The ureters from these either enter the lower urinary tract separately in a complete duplex (40 per cent of cases) or join above the bladder and drain via a common orifice in an incomplete duplex (60 per cent of cases). The position of the ureteric orifice on the trigone may be called ectopic, when it is away from the expected ureteric position (either lateral or medial to it).
