Since the dilatation of ureterovesical junction structure in Robo2 mutant mice was too severe to be corrected by postnatal trigone or ureteral maturation and remodeling, we found no spontaneous resolution of hydronephrosis in Robo2 mutant mice with congenital golf-hole like wide-open ureteral orifice detected at birth. Here, ROBO2 is linked to hydronephrosis.