Crossing renal vessel causing ureteropelvic junction obstruction.

Ureteropelvic junction UPJ obstruction is caused by the presence of an aperistaltic dysplastic segment at the UPJ. Besides this intrinsic etiology, extrinsic factors, mainly crossing vessels, maybe 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 the advent of advanced imaging techniques such as multidetector row computed tomography MDCT and fast magnetic resonance imaging. We present a similar case where MDCT proved the crossing renal vessel to be the cause for UPJ obstruction.