Hydronephrosis.

It is essential to distinguish between an obstructed and an unobstructed hydronephrosis as the management of the two types is quite different. Some of the radiographic and isotopic methods of distinguishing these two leave much to be desired and the place of dynamic studies is discussed. The aetiology of pelviureteric junction obstruction remains uncertain, but it is probable that one or more of several factors may be involved and these are discussed. The types of hydroenphrosis are classified as chronic, intermittent, unsuspected, equivocal, and reflux-induced.