The aim of this study was to evaluate diuresis renography with an intravenous injection of furosemide 20 minutes after administering the radiopharmaceutical (F+20 protocol) or 15 minutes before (F-15 protocol) in patients with upper urinary tract dilatation.Twenty-one patients with pyelocaliceal system dilatation, but not ureteral dilatation, on ultrasonography were evaluated. The patients underwent diuresis renography using the F+20 and F-15 protocols. Renal scan findings and kidney split function were recorded. Then, the patients underwent surgical or conservative treatment according to their clinical conditions and imaging results. Follow-up was done 3 and 6 months postoperatively by physical examination, intravenous urography, and diuresis renography.Eleven patients (52.4%) had complete obstruction in both protocols of renography, and 5 (23.8%) had an equivocal result in the F+20 and an obstructive pattern in the F-15. These patients underwent surgical operation. In 3 patients (14.3%), both protocols demonstrated a normal urinary tract. In 2 patients (9.5%), a nonobstructive response in the F+20 and an equivocal result in the F-15 were seen. One of them underwent surgical operation because of impaired kidney function during the follow-up and 1 was treated conservatively. Overall, obstruction was found in 16 out of 21 patients (76.2%) by the F-15 protocol, while it was found in 11 (52.4%) by the F+20 protocol (P=.01). The mean kidney split function was 55.15% +/- 7.82% and 54.81% +/- 6.87% in F+20 and F-15 protocols, respectively (P=.45).Using the F-15 protocol may reduce the equivocal results of the F+20 for diuresis renography.