Impact of age on effects of ureteral obstruction on renal function.

Chronic partial ureteral obstruction of the urinary tract is a common congenital abnormality. Yet, its impact on the function of the kidney in the young has not been examined. To determine the relationship between age at the time of injury and outcome, partial ureteral obstruction was produced in guinea pigs during the first, second, third, fourth, or fifth week of life, and several variables of glomerular, proximal and distal tubular functions were measured 4 weeks later. The results were compared with those obtained in the contralateral kidney and with those observed in age-matched sham-operated animals. There was a significant impairment in the growth of the obstructed kidney. The weight of the contralateral kidney in the experimental animals was significantly greater than that of the obstructed (P less than 0.001) or control (P less than 0.005) kidney, but compensatory hypertrophy decreased progressively with age, being 30% of control when the obstruction was produced in the second week of life and only 2% when the obstruction occurred at 5 weeks of age. Obstruction resulted in a marked reduction in GFR at all ages, the impairment being inversely proportional with age. Conversely, the increase in GFR on the contralateral side, which was proportional with the increase in renal mass, diminished from 60.1 to 20.5% (r = 0.96, P less than 0.001) as a function age. Tubular reabsorption of phosphate was significantly lower in obstructed kidneys, particularly so in the animals sustaining obstruction during the first 2 weeks of life.(ABSTRACT TRUNCATED AT 250 WORDS)