LONG-TERM FOLLOW-UP OF RENAL FUNCTIONAL RESERVE CAPACITY AFTER UNILATERAL NEPHRECTOMY IN CHILDHOOD

Purpose: We establish renal function and renal reserve capacity in the long-term followup of unilateral nephrectomy in childhood. Materials and Methods: We recalled 37 subjects who underwent; unilateral nephrec tomy during childhood (age less than 16 years) to determine glomerular filtration rate, renal plasma flow and functional renal reserve capac ity after oral protein loading. Interval since nephrectomy was 0.5 to 10 years in 10 cases, 11 to 20 in 13 and more than 20 years in 14, dur ing which regular repeated renal function tests were done at our hospi tal. None of the patients had hypertension or significant proteinuria and all developed normally into adults. A group of 7 healthy normal su bjects with 2 kidneys served as controls. Results: Creatinine clearanc e increased 34% immediately after surgery from a mean plus or minus st andard error value of 78.6 +/- 6 to 105.4 +/- 7.2 ml. per minute per 1 .73 m.(2), peaked 2 to 6 months postoperatively and then plateaued (ap proximately 125 ml. per minute per 1.73 m.(2)). This level of renal fu nction was sustained for more than 20 years. At the present testing gl omerular filtration rate and renal plasma flow were not different from those of the controls. Renal reserve capacity was normal (stable) onl y during the first decade after unilateral nephrectomy (approximately 6% decrease), and it decreased by 50% at 10 to 20 and 66% at 20 to 30 years later. Conclusions: This long-term followup study demonstrates t hat a single remnant human kidney continues to function normally for m ore than 20 years. The prolonged increased workload does not interfere with normal development and maturation. The renal reserve capacity de creased significantly during the years may, however, indicate a vulner ability of the single kidney and raises the possibility of renal funct ional impairment with much longer followup.