Diuretic renal scan: is it always reliable?

The differentiation between significant mechanical obstruction and nonobstructive dilation of the kidneys and ureters is fundamental to patient management. The diuretic renal scan is a useful test in this situation because it usually is reliable and reproducible and is noninvasive and objective, providing information about the function of each kidney. However, this study has given variable results in a small number of patients. We report our experience with five such patients and recommend an algorithm for evaluating patients with equivocal scan results. This report emphasizes the importance of continued follow-up and the need for periodic reevaluation of patients with unexplained urinary symptoms or persistent flank pain, even when the initial diuretic renal scan is normal.