Abstract
The Hospital for Sick Children, University of Toronto, Toronto, Canada PURPOSE: Determination of DRF by DMSA or DTPA renal scans has an important role in the management of congenital hydronephrosis. An experimental model of partial unilateral ureteral obstruction was devised in order to evaluate the ability of these scans to accurately reflect DRF defined by inulin clearance. METHODS: Twenty seven young male NZ rabbits were studied. Initial DRF was determined in each animal by DMSA and DTPA renal scans. In the experimental group (n=19), a 1-cm segment of left upper ureter was buried in psoas muscle in order to create a partial obstruction. Following 8 to 24 weeks of observation, both renal scans were repeated. Partial obstruction was confirmed by means of lasix washout scan, IVP and antegrade urogram. All animals underwent laparotomy. Ureters were divided distal to obstruction and urine was collected separately from each ureter in order to calculate single kidney inulin clearances. In the unobstructed control group (n=8) after the initial DTPA and DMSA scans, a similar procedure was performed to determine inulin clearance. The results of DRF were compared using paired two tail t-test. RESULTS: Left Kidney Mean DRF ± S.D.(%) Control Experimental Group Post obstruction change Group pre obstruct post obstruct DMSA 51 ± 1.3 51 ± 1.7 44.9 ± 1.8 DTPA 56.8 ± 4.6 53 ± 2.9 48 ± 6.5 Inulin 50 ± 5.4 33.3 ± 13 Inulin DTPA DTPA DTPA P<0.001 P<0.001 P<0.06 Urine volumes produced by obstructed kidney were significantly lower (p< 0.001). Urine culture was negative in all animals. In the partially obstructed kidney inulin derived DRF is significantly lower than that measured by DMSA or DTPA renal scans. CONCLUSION: In the non obstructed kidney DRF measured by DMSA, but not DTPA, correlates well with DRF derived from inulin clearance. In the setting of partial obstruction DRF measured by both DMSA and DTPA scans does not correlate with DRF derived from inulin clearance.