While the effect of uninephrectomy on loss of GFR is a cardinal issue for potential kidney donors, current information relies on surrogates of unknown validity, such as those from creatinine-based estimating equations and urinary clearance methods.

Hence, a random sample of our donor population was selected to undergo serial iohexol GFR testing. Testing began in 2005 and participants were invited to return for repeat measurements every 3 years thereafter.

The mean age of the 214 donors with two GFR measurements was 52.9 ± 9.8 at the first GFR assessment, performed 12.1 ± 8.9 years after donation; 79% were related to the recipient and 61% female.

Median GFR was 70.5 (mL/min/1.73 m2) at the first assessment. In the 4.8±1.3 year interval between GFR assessments, GFR declined slowly, at a median (IQR) rate of -0.3 (-1.4, 0.6) per year. Overall, there was a 0.05 ml/min/1.73 m² decline in GFR for additional year of age (Figure 1).

In those with a decline in GFR, the rate was -1.6±1.5 ml/min/1.73 m²/yr, compared with +1.3±1.5 ml/min/1.73m²/yr in those with an increase. There were no differences in these two donor groups, apart from a modestly higher prevalence of hypertension (Table 1).

These data suggest that GFR declines slowly after transplant donation and that long-term hyperfiltration is common.

Figure 1. Change in mGFR by age at second visit

Table 1. Pre and Post-donation variables by change in mGFR (values expressed as mean±SD or %)

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