Purpose: We studied dynamic changes in total volume and renal vein blood flow in the kidneys contralateral to partial ureteral obstruction induced in newborn rats.
Materials and methods: Using magnetic resonance imaging we investigated changes in total kidney volume and renal vein blood flow in 20 rats with mild and 18 with severe partial ureteral obstruction that was induced on the left side 2 days after birth. A total of 15 sham operated control rats were also studied. Total kidney volume and renal vein blood flow were monitored sequentially every 2 to 6 weeks for a total of 24 weeks. Renal parenchymal volume measured in vivo by magnetic resonance imaging was compared with that measured in vitro at week 24.
Results: Total volume and renal vein blood flow increased significantly in contralateral nonobstructed kidneys from week 14 and thereafter in rats with severe partial unilateral ureteral obstruction. At week 24 volume had increased by 22% and blood flow had increased by 25%. Volume and flow did not increase significantly in contralateral nonobstructed kidneys in rats with mild partial unilateral ureteral obstruction (p = 0.09). Before changes occurred in volume and blood flow in the contralateral nonobstructed kidneys, renal vein blood flow had decreased significantly from week 8 and thereafter in severely obstructed kidneys. In rats with mild partial unilateral ureteral obstruction renal vein blood flow decreased significantly in obstructed kidneys from week 18 and thereafter. Good correlation was noted between MRI in vivo and in vitro kidney volume measurements (r = 0.972, p <0.001).
Conclusions: A significant increase in total volume and renal vein blood flow in contralateral nonobstructed kidneys did not develop immediately after the onset of detectable functional deterioration in partially obstructed kidneys. Therefore, caution should be used when incorporating compensatory growth into surgical decision making.