Renal Doppler ultrasound in children with normal upper urinary tracts: effect of fasting, hydration with normal saline, and furosemide administration.

OBJECTIVES

To study the age dependency of renal resistive index (RI) and to study the effect on the renal RI of fasting, intravenous infusion of normal saline, and administration of furosemide in children with normal upper urinary tracts.

METHODS

The study included 28 nonobstructed renal units in 15 boys ranging in age from 3 to 11 years. Diuretic renography and Doppler ultrasonography were attempted in all children. Doppler ultrasonography was carried out under three different conditions: fasting state, 30 to 60 minutes after intravenous infusion of normal saline (15 mL/kg), and 10 minutes after administration of furosemide (1 mg/kg; maximum, 40 mg).

RESULTS

There was an inverse correlation between age and RI of both renal units under the three conditions of Doppler studies. At fasting state mean RI was 0.70 +/- 0.04, whereas 15 of 28 renal units (54%) had an RI of 0.70 or higher. Intravenous infusion of normal saline significantly decreased the RI to 0.63 +/- 0.04 (P < 0.000001). Injection of furosemide caused a further significant decrease of RI from 0.63 +/- 0.04 to 0.60 +/- 0.04 (P < 0.002).

CONCLUSIONS

The renal RI in healthy children is age dependent. In the fasting state, 54% of nonobstructed renal units in children have an RI of 0.70 or higher. Intravenous infusion of normal saline and administration of furosemide can independently cause a significant decrease of the RI in nonobstructed renal units in children.