Persistent fetal ureter.

Six patients have been seen with a peculiar ureteral lesion that has not been described previously. The lesion is characterized by either local segmentation or convolution and may represent either a persistent fetal ureter or a form of ureteral dysgenesis. Proximal dilatation, when present, has been less than the original radiographic appearance of high grade obstruction would lead one to expect. The ureteral lesions have disappeared progressively, suggesting that a period of conservative observation is warranted in similar situations.