Congenital midureteral obstruction.

Congenital midureteral obstruction, caused either by a ureteral valve or stricture, is an exceedingly rare entity. When encountered, it is generally misdiagnosed as either primary megaureter or ureteropelvic junction obstruction, leading to a less than optimal surgical approach. Seven children with midureteral obstruction were seen over the past 17 years. Two of the patients presented with hydronephrosis on prenatal ultrasonography, and five with urinary tract infection. In only three was the diagnosis suspected on intravenous urography and voiding cystourethrography alone. Five of the seven cases had either antegrade or retrograde pyelography, prior to or at the time of their operative procedure, and in four of these a correct diagnosis was made. Notably, in five of the seven cases, recognition of the midureteral lesion prior to the surgical incision allowed the approach to be modified and a more appropriate technique (ureteroureterostomy) to be performed. The etiology of midureteral valve and stricture has been attributed to improper recanalization, insufficient vascular supply, or persistence of ureteral folds. Three of our patients had contralateral renal dysgenesis, suggesting an underlying ureteral bud abnormality.