Ureteropelvic junction obstruction in anomalous kidneys

The majority of UPJ obstructions occur in otherwise normal kidneys; however, a small percentage of UPJ obstructions occur in anomalous kidneys. The most frequently reported associated anomalies are horseshoe kidneys, kidneys with duplicated collecting systems, and ectopic kidneys. Special consideration must be given to the diagnosis of a UPJ obstruction in an anomalous kidney, and, once diagnosed, the management must be tailored accordingly.