Background

Kidney transplantation from living donors is an important treatment for patients with kidney failure. An accurate evaluation of renal function must be conducted before and after living donor nephrectomy (LDN) to minimize the risk to the donor. The determination of renal inulin clearance (Cin) is considered the gold standard for measuring GFR, but the method is time-consuming and not widely available.

Subjects and Methods

Clinical data were collected from 78 living kidney donors. who had undergone measurements of Cin before and one year after LDN. Each subject had three consecutive serum and urine samples under continuous intravenous inulin infusion. The mean of three Cin values was used as the measured GFR (mGFR). We compared the accuracy of the eGFR based on serum creatinine (eGFRcr) and based on serum cystatin C (eGFRcy) with that of mGFR value for assessing renal function in kidney donors.

Results

The mean mGFR was 96.9 ± 14.5 ml/min/1.73 m² before LDN, and 64.5 ± 9.5 ml/min/1.73 m² after LDN. The correlation coefficient between mGFR before LDN and after LDN was 0.6121. The correlation coefficient between eGFRcr and mGFR before and after LDN was 0.565 and 0.715, respectively. The mean difference between the two values was −25.1 with a root mean square error (RMSE) of 12.1 and −16.6 with a RMSE of 6.9. The percentage of calculated eGFRcr values within 30% of the mGFR was 59.3% and 68.5%. The correlation coefficient between eGFRcy and mGFR before and after LDN was 0.409 and 0.610, respectively. The mean difference between the two values was −5.5 with a RMSE of 16.1 and −2.2 with a RMSE of 10.8. The percentage of calculated eGFRcy values within 30% of the mGFR was 91.5% and 94.5%. The mean difference was significantly lower in eGFRcy than in eGFRcr (p<0.001), and the percentage within 30% was significantly higher in eGFRcy than in eGFRcr (p<0.001). eGFRcr underestimated the mGFR in 98.7% of the cases before LDN, and underestimated the mGFR in 98.7% of the cases after LDN. Whereas eGFRcy underestimated the mGFR in 69.5% of the cases before LDN, and underestimated the mGFR in 41.1% of the cases after LDN.

Conclusion

eGFRcy might be more helpful to evaluate the renal function of living kidney donors before and after LDN than eGFRcr. Continued evaluation of data is essential to safeguard the quality and health of all living kidney donors.

CITATION INFORMATION: Kakuta Y., Okumi M., Imamura R., Ichimaru N., Takahara S., Ishida H., Tanabe K. Estimated GFR for Living Kidney Donor Evaluation before and after Donor Nephrectomy Am J Transplant. 2017;17 (suppl 3).

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