We report on 4 cases with a unilateral single ectopic ureter associated with ipsilateral
dysplastic or hypoplastic kidney and the usefulness of preoperative magnetic
resonance(MR) urography in revealing the ureteral course and detecting the insertion
site of ectopic ureter Among two cases of unilateral single ectopic ureter associated
with dysplastic kidney, one drains into the seminal vesicle and the other drains into th8
urethra. The other two cases have unilateral single ectopic ureter associated with
hypoplastic kidney that drain into the vagina. In all cases, MR urography shows the
ureteral course and insertion site of ectopic ureter regardless of the renal function. We
believe that MR urograhy is a useful technique for the diagnosis of unilateral single
ectopic ureter associated with hypofunctioning kidney.