Extrinsic ureteropelvic junction obstruction from a crossing renal vessel:demography and imaging

Background.The increase in the use of prenatal ultrasound has revolutionize d the detection of hydronephrosis and has had an unanticipated consequence. Objective. To describe the new demographics of symptomatic ureteropelvic ju nction (UPJ) obstruction and the characteristic imaging findings, when the obstruction is extrinsic, from a crossing renal vessel. Materials and methods. From a uroradiology database (1994 through 1999) we identified children with surgically corrected UPJ obstruction from intrinsi c and extrinsic causes. Results. One hundred children had symptomatic UPJ o bstruction treated by surgery In 51 (49 %), obstruction was due to a crossi ng vessel. One hundred and one had UPJ obstruction detected by prenatal son ography. Only 11(11 %) were due to a vessel. Two clinical and imaging findi ngs were strongly suggestive of obstruction from a vessel: (1) in 5 of the 100 children the symptoms (pain, nausea, and vomiting) were intermittent. O nly when symptoms were present were there hydronephrosis and obstruction; ( 2) in 51 of the 100 children a short segment of ureter, just below the UPJ, was filled with contrast or urine (on renal sonography, intravenous urogra phy, or retrograde/antegrade ureterography). Conclusions. Extrinsic UPJ obstruction caused by a vessel is an uncommon ca use of obstruction when all patients are considered. However, in symptomati c older patients whose hydronephrosis was not first identified on prenatal sonography, a vessel was the cause of obstruction in one-half.