RENAL FUNCTION OUTCOME IN UNILATERAL HYDRONEPHROSIS IN NEWBORN PIGS. II. FUNCTION AND VOLUME OF CONTRALATERAL KIDNEYS

PURPOSE: We evaluated the compensatory response of contralateral kidney growth and function in pigs with unilateral hydronephrosis. MATERIALS AND METHODS: Unilateral partial ureteral obstruction causing severe hydronephrosis was induced at age 2 days in 12 piglets, while 10 underwent sham operation. At ages 4, 12 and 24 weeks single kidney function was assessed using 99mtechnetium diethylenetriaminepentaacetic acid differential uptake on renography combined with the glomerular filtration rate estimated from the plasma clearance of 99mtechnetium diethylenetriaminepentaacetic acid. Kidney size was measured in parallel by magnetic resonance imaging. RESULTS: At 4 weeks the glomerular filtration rate and volume of the contralateral kidneys did not differ from those in controls, although obstructed kidney function was significantly decreased. At 12 weeks the mean glomerular filtration rate plus or minus standard error of mean of the contralateral kidneys significantly increased to 1.60 +/- 0.11 versus 1.33 +/- 0.11 ml. per minute per kg. (p <0. 05), whereas kidney volume did not differ from that in sham operated controls. At 24 weeks the glomerular filtration rate and volume of the contralateral kidneys did not differ from those in controls. Glomerular filtration rate and volume of the contralateral kidneys did not correlate at 4 weeks but they correlated at 12 and 24 weeks (r = 0.94 and 0.89, respectively). CONCLUSIONS: Initially kidneys contralateral to obstructed kidneys with decreased function had no increased growth or function. Furthermore, function and volume of the contralateral kidneys were not associated at the early age. Thus, the results of our study imply that determining the size (growth) or function of the contralateral kidney at an early age does not predict function decrease in a partially obstructed kidney in this pig model.