We designed a following experiment to appraise the effect of unilateral hydronephrosis on the contralateral kidney using weanling rats whose kidneys were in a growing stage.
Rats were divided into 4 groups. Complete unilateral (left) ureteral obstruction (CUUO) was made on the experiment rats, and these went through the following procedures on the day 3 after CUUO; 1) Group R: CUUO released, 2) Group N: left nephrectomy performed, 3) Group S: CUUO continued. Sham-operations were performed on the days 0 and 3 to the controls. Renal cortical blood flow and glomerular volume of the contralateral (right) kidneys were determined on the days 5, 7, 9, 14 and 21.
Blood flow to the renal cortex per unit volume (ml/min/100cm³; measured with Laser blood perfusion monitor) in the contralateral kidneys increased gradually in the all groups, but statistical significance was not confirmed in the observed period between any groups. Increases in total renal blood flow (wet kidney weight times renal cortical blood flow per unit volume; g×ml/min/100cm³) were proportional to the measured wet kidney weight in the all groups. Notably in the group N, a significant increase was noted compared to the group R and the controls.
Glomerular volume (GV) of the contralateral kidneys did not show significant changes on the day 3 compared to the controls. GV significantly grew up during the day 5 to the day 14 (2 to 11 days after the relief of CUUO) in the group R and then it settled to the level of the controls on the day 21. In contrast, GV in the group N and the group S still continued to grow up (statistically significant) on the day 21. GV in the group R did not correlate to total renal blood flow after the day 14 although total renal blood flow continued to increase gradually. Proprotional increases in total renal blood flow and GV were observed in group N and group S.
These results suggest that some factors, other than increase of renal blood flow, are playing roles on enlargement of glomerular volume after a relief of CUUO.