Identifiable changes in the pulse contour of antegrade vertebral artery waveforms seem to represent the early stages of subclavian steal physiology. These changes can be organized into waveform types that indicate increasingly abnormal hemodynamics.

The 99mtechnetium-diethylenetriaminepentaacetic acid renal scan allows differentiation of ureteropelvic junction obstruction from multicystic kidney in most instances. Although renal function usually will improve at least a little after relief of obstruction, the young infant is privileged and more improvement can be expected than occurs usually in older children. Since an operation is as safe and results of pyeloplasty are as good in the neonate as in older infants or children early correction of ureteropelvic junction obstruction is advocated in otherwise healthy infants as soon as the diagnosis is established.