Introduction

In former years, the clinical management of upper tract dilation was simple. Because most children with hydronephrosis presented with a mass or a clinical problem such as infection or pain, it was assumed that the cause was an obstruction. Surgical treatment was performed and the outcome was usually satisfactory. The advent of prenatal ultrasonography and the resultant identification of large numbers of asymptomatic upper tract dilation has forced physicians to alter their understanding of the significance of hydronephrosis and to better define obstruction. This is largely because dilation often improves or resolves spontaneously, which questions the necessity of surgical treatment. Whereas in the past only few natural history studies were available, a greater appreciation of the spontaneous resolution of prenatally detected hydronephrosis has been gleaned from multiple studies from various centers around the world.

Any analysis of long-term outcomes of upper tract dilation management must of necessity deal separately with the symptomatic and asymptomatic varieties and must also recognize that dilation involving the kidney alone is different from dilation affecting kidney and ureter together. Accordingly, this chapter will be divided into two sections. The first will deal with pure hydronephrosis and consider the child with dilated renal collecting systems without ureteral dilation. The second portion will examine hydroureteronephrosis and dilation of both the renal collecting system and ureter.

Dilation of the renal collecting system is easily diagnosed on radiographic imaging studies. However, not all upper tract dilation is caused by obstruction.