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 nephrectomy during childhood (age less than 16 years) to determine glomerular filtration rate, renal plasma flow and functional renal reserve capacity 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, during which regular repeated renal function tests were done at our hospital. None of the patients had hypertension or significant proteinuria and all developed normally into adults. A group of 7 healthy normal subjects with 2 kidneys served as controls. RESULTS: Creatinine clearance increased 34% immediately after surgery from a mean plus or minus standard 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 (approximately 125 ml. per minute per 1.73 m.2). This level of renal function was sustained for more than 20 years. At the present testing glomerular filtration rate and renal plasma flow were not different from those of the controls. Renal reserve capacity was normal (stable) only 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 that a single remnant human kidney continues to function normally for more than 20 years. The prolonged increased workload does not interfere with normal development and maturation. The renal reserve capacity decreased significantly during the years may, however, indicate a vulnerability of the single kidney and raises the possibility of renal functional impairment with much longer followup.
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