Congenital hydronephrosis of lower segment in duplex kidney.

Congenital hydronephrosis of the lower segment in duplex kidney was treated in 12 patients. This uncommon abnormality carries the risk of calculous formation, chronic urinary tract infection, and functional failure of the involved segment. Diagnostic problems encountered included differentiation from tumor, obstruction by a calculus, and hydronephrosis due to reflux. Treatment was individualized according to severity of hydronephrosis and presence or absence of specific complications. Mild obstruction could be treated nonsurgically while the patient was closely observed for evidence of stone, infection, or worsening of obstruction. Available surgical procedures include end to side or side to side pyeloureteral anastomosis, plastic widening of a narrowed obstructive site, removal of calculus with relief of obstruction, and heminephrectomy.