Radiologic evaluations affecting surgical technique in ureteropelvic junction obstruction.

Ureteropelvic junction obstructions can be explored by radiographic methods including ultrasonography, intravenous pyelography, radionuclide scanning, magnetic resonance imaging and computerized tomography. The decision to operate on an ureteropelvic stricture is best given by the results of a radionuclide scan, which can demonstrate the obstruction. The operative technique is influenced by the presence of a polar artery, as this presence represents a danger when endopyelotomy is performed. The presence of a polar artery may be demonstrated by computerized tomography using helicoidal reconstruction. Magnetic resonance imaging with injection of gadolinium is also useful when available. The outcome and the results of the surgical procedure are also evaluated by radionuclide scanning.