title: Extrinsic ureteropelvic junction obstruction from a crossing renal vessel: demography and imaging.
abstract: BACKGROUND
  The increase in the use of prenatal ultrasound has revolutionized the detection of hydronephrosis and has had an unanticipated consequence.
  
  
  OBJECTIVE
  To describe the new demographics of symptomatic ureteropelvic junction (UPJ) obstruction and the characteristic imaging findings, when the obstruction is extrinsic, from a crossing renal vessel.
  
  
  METHODS
  From a uroradiology database (1994 through 1999) we identified children with surgically corrected UPJ obstruction from intrinsic and extrinsic causes.
  
  
  RESULTS
  One hundred children had symptomatic UPJ obstruction treated by surgery. In 51 (49 %), obstruction was due to a crossing vessel. One hundred and one had UPJ obstruction detected by prenatal sonography. Only 11 (11%) were due to a vessel. Two clinical and imaging findings were strongly suggestive of obstruction from a vessel: (1) in 5 of the 100 children the symptoms (pain, nausea, and vomiting) were intermittent. Only 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 urography, or retrograde/antegrade ureterography).
  
  
  CONCLUSIONS
  Extrinsic UPJ obstruction caused by a vessel is an uncommon cause of obstruction when all patients are considered. However, in symptomatic older patients whose hydronephrosis was not first identified on prenatal sonography, a vessel was the cause of obstruction in one half.
authors.affiliation: Children's Hospital and Harvard Medical School, Department of Radiology, Boston, MA 02115, USA.
authors.forename: V J
authors.initials: VJ
authors.lastname: Rooks
authors.forename: R L
authors.initials: RL
authors.lastname: Lebowitz
mesh_terms: D002648:Child; D002675:Child, Preschool; D003710:Demography; D003952:Diagnostic Imaging; D005260:Female; D006801:Humans; D007682:Kidney Pelvis / Q000473:pathology / Q000601:surgery; D008297:Male; D011296:Prenatal Diagnosis; D012077:Renal Artery / Q000473:pathology*; D012082:Renal Veins / Q000473:pathology*; D014517:Ureteral Obstruction / Q000175:diagnosis* / Q000209:etiology* / Q000601:surgery