Ureteropelvic junction obstruction


  • Obstruction of the flow of urine from the renal pelvis to the proximal ureter due to partial or total blockage at the ureteropelvic junction that can be congential or acquired

  • Can be caused by structural abnormality (intrinsic disorganization, extrinsic compression mainly from crossing vessels) or by functional anomaly

Clinical features


  • Most common cause of pediatric hydronephrosis, occurring in 1 per 1000–2000 newborns

  • Sporadic in most cases, with rare familial association

  • May present at any age

  • In children

    • 20%–30% bilateral

    • Predominantly in boys (> 2:1 (M:F) in neonates) and on the left side (67%)

    • Congenital

  • Due to embryologic defects in the proximal ureter that has altered circular musculature development and/or collagen fibers, and composition between and around the muscle cells (75%)

  • Rarely valvular mucosal folds, persistent fetal ureteral convolutions, and ureteral polyps

  • Extrinsic compression by aberrant or accessory renal artery or arterial branch (6%–24%)

  • Abnormally high insertion of ureter

    • Other concomitant genitourinary anomalies: horseshoe kidney, CHARGE (coloboma, heart anomaly, choanal atresia, retarded growth, and genital and ear anomalies) syndrome

  • In adults

    • Predominantly in women

    • Most often unilateral

    • Etiology: kidney stones, upper urinary tract inflammation, scarring from a past surgery, or tumors

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