Antenatal hydronephrosis: ureteral polyp causing ureteropelvic junction obstruction.

We describe a rare case of ureteropelvic junction obstruction in a three and a half-year-old boy due to a benign ureteric polyp. This case is being reported due to the rarity of benign neoplasms of the ureter in infants and children and also because the child had been diagnosed antenatally as having hydronephrosis.