[Effect of unilateral hydronephrosis upon contralateral renal growth]

To evaluate the effect of hydronephrosis on the growth of contralateral normal kidney, following experiment was designed and performed.

Three to four weeks old S-D rats weighing 80-90 g were used. The kidney development of these rats is considered to be roughly equivalent to that of a one year old child. Those rats were divided into three groups: (1) left nephrectomy (group N), (2) left ureteral ligation (group H), and (3) sham operation (group S). Bromodeoxy uridine (BrdU) was administered intraperitoneally on the 1st, 3rd, 5th, 7th and 14th days after operations. One hour after injection of BrdU, right kidneys were removed and wet weight and labelling index (LI) of BrdU were calculated. Compensatory renal growth of right kidneys was observed in both group H and group N on and after 1st or 3rd day. In group N, the growth was accompanied by cellular proliferation, while in group H, hypertrophy was the major finding for up to 5th day. From 7th day on, when significant disorders became histologically evident in the left hydronephrotic kidneys, cell proliferation was also observed in the group H. The above results indicate that compensatory renal growth occurred in the contralateral normal kidney after unilateral ureteral ligation. Although proliferation of right renal tubular cells were recognized when significant tubular and interstitial damage of the left hydronephrotic kidneys were observed, hypertrophy was a major finding in an early stage. We suggest that these results were attributed to (1) reduction of nephron triggered to proliferate tubular cells and (2) the existence of hydronephrotic kidney inhibited tubular cell proliferation.