Value of multidetector ct in preoperative assessment of ureteropelvic junction obstruction

Ureteropelvic junction (UPJ) obstruction may be caused by the presence of an aperistaltic dysplastic segment at the UPJ. Besides this intrinsic etiology, extrinsic factors, mainly crossing vessels, may be the causative factor. The controversy regarding the functional significance of vessels crossing at the UPJ is not a new one, though this debate has been resurrected in recent years because of improved detection due to advent of advanced imaging techniques like multidetector row computed tomography (MDCT) and fast magnetic resonance imaging. We present two similar cases where MDCT proved the crossing renal vessel (CRV) to be the cause for UPJ obstruction.