Primary non-refluxing, non-obstructed megaureter is a rare condition among the megaureter.

A 11 month old monozygote twin baby had been admitted due to blood and pus tinged spotson a diaper. Although the excretory urogram showed moderately dilated left ureter, but the voiding cystogram and diruetic renogram showed no reflux and no obstruction. So we diagnosed as a primary non-refluxing, non-obstructed megaureter.

We report this case with the review of literatures.