Nephrogenic diabetes insipidus: A cause of severe nonobstructive urinary tract dilatation

The presentation of bilateral urinary tract dilatation in the pediatric age group invokes a familiar differential diagnosis, including bladder outlet obstruction, reflux nephropathy, and primary megaureter. However, it is now well established that urine over-production can create a functional obstruction with secondary and often massive urinary tract dilatation. NDI is an established cause of urinary tract dilatation. The first case of NDI associated with dilatation of the urinary tract was described by Waring and coworkers in 1945. The bulk of the literature describing the effects of NDI is found in the urologic and pediatric literature; very little has been written in imaging journals and texts regarding this diagnosis. We describe the ultrasonographic appearance of urinary tract effects of NDI.