Crossing Into the Unknown. A Peculiar Cause of Ureteropelvic Junction Obstruction in a 14-Year-Old Boy

Ureteropelvic junction obstruction (UPJO) is a common cause of upper urinary tract obstruction and consequent hydronephrosis. We present a case of right UPJO caused by a crossing vessel suspected to be the right second lumbar vein. While crossing vessels are a common cause of UPJO in older children and adults, they are usually attributed to lower pole vessels. We believe that this is the first case report of UPJO caused by a lumbar vein. …