Compensatory renal hypertrophy and changes of renal function following nephrectomy

Abstract

腎摘除術後の対側腎の体積と腎機能の変移を検討した.対象は腎細胞癌で腎摘除術を受け, 対側腎に明らかな異常がなく, 当院で少なくとも2年以上経過観察している25例であった.25例中12例で毎年CT検査を受けていた.腎の体積は造影CT上の腎の3方向の径を測定し楕円体体積の公式に当てはめて求めた。対側腎の体積は術後3年目まで増加し, 術前体積(100%)に比べて2～7年後の平均最終体積は120%であった.対側腎の腎摘前の体積と術後の最終体積の間に有意な相関はなかったが, 術前に小さい腎は腎摘後の最終体積比率が大きい傾向にあった.血清クレアチニン値は術後1年目に有意に増加したが, 1年目の値に比べてその後数年の経過で有意に低下した.つまり, 代償性腎肥大と腎機能の改善は術後数年以内に完成されるものの, 腎肥大に比べて血清クレアチニン値の改善は遅れた.この理由として, 術後早期の腎血漿流量の増加に伴って代償性腎肥大は起こるが, 糸球体濾過率の上昇は2-一一3年遅れるため, 上昇していた血清クレアチニン値の低下も遅れたことが考えられた.

We studied the changes in the serum creatinine level and the volume of the remaining kidney following nephrectomy using contrast-enhanced compounded tomogram (CT) scans. Twenty-five patients undergoing nephrectomy for renal cell carcinoma without obvious disease in the remaining kidney were carefully followed for a period of at least two years at our hospital. Twelve patients received follow-up CT scans each year after nephrectomy. The ellipsoid volume of the kidney was calculated by measuring the 3-dimensional size on CT scans. The mean relative volume (%) of the remaining kidney increased up to year 3 postoperatively, and the final mean relative volume at varying periods from years 2 to 7 was 120%. Kidneys that were smaller prior to nephrectomy showed a tendency to have a larger final relative volume after nephrectomy, although there was no significant correlation between the kidney volume prior to nephrectomy and at final measurement. The mean serum creatinine level was significantly increased at one year after nephrectomy, but it decreased significantly over time. Therefore, both compensatory renal hypertrophy and improved renal function seemed to be established within several years after nephrectomy. However, the improvement of serum creatinine was delayed compared with the increase of kidney volume. That is, renal plasma flow might be increased early by compensatory renal hypertrophy, followed within a few years by an increase in glomerular filtration and a decrease of serum creatinine.