Vascular anatomy at the ureteropelvic junction.

In 65% of the cases regarding the ventral surface of the UPJ, there was a prominent artery, vein, or both in close relation to the ventral surface of the UPJ. In only 6.8% there was an inferior polar artery crossing anteriorly to the UPJ. Therefore, many of the vessels visualized close to the UPJ and described as anomalous and etiologic in obstruction are normal segmental arteries that do not cause UPJ obstruction. In 26.7% of cases regarding the dorsal surface of the UPJ, there was a vessel crossing at or lower than 1.5 cm above the posterior surface of the UPJ. On the basis of our anatomic findings, we advise that in endopyelotomy, the incision along the stenotic UPJ be created only at its lateral aspect.