Contralateral renal hyperplasia and increased renal function after relief of chronic unilateral ureteral obstruction

Following relief of 1, 2 or 3 weeks of unilateral ureteral obstruction, contralateral compensatory renal growth and increased renal function were measured 3 and 6 months later. Compensatory growth occurred predominantly by hyperplasia, demonstrated by a significant increase in DNA content and a decrease in the RNA:DNA ratio (p less than 0.04). This is in contrast to compensatory growth following nephrectomy or unrelieved unilateral ureteral obstruction, which occurred primarily by hypertrophy with no significant change in DNA content but a significant increase in RNA content and the RNA:DNA ratio (p less than 0.04). Contralateral renal function in animals with relieved unilateral ureteral obstruction was greater than in controls with 2 normal kidneys (p less than 0.05). The contralateral increase in renal function was greater than that in animals subjected to ipsilateral nephrectomy or unrelieved ureteral obstruction, but this did not reach statistical significance. Thus, when growth occurred by hyperplasia, there was a trend to greater increases in renal function than when growth occurred by hypertrophy. Contralateral compensatory renal hyperplasia and increased renal function occurred in conjunction with a decrease in renal mass and function of the ipsilateral post-obstructed kidney. These experiments suggest that the post-obstructed, poorly functioning kidney stimulates contralateral hyperplastic growth and increased renal function. This hyperplastic response is different from the hypertrophic response following nephrectomy or unrelieved unilateral ureteral obstruction, implicating the post-obstructed kidney as the stimulus of the hyperplastic response.