Is cystatin C valuable marker of glomerular filtration rate in living kidney donors after uninephrectomy?

BACKGROUND The determination of kidney function plays a pivotal role in living donors renal assessment because of the long-term hazards of life with one kidney. Guidelines recommend estimation of glomerular filtration rate (GFR) by the Modification of Renal Disease (MDRD) or Cockroft-Gault equations for people with normal or near-normal renal function. Cystatin C (CysC) has been introduced as an alternative endogenous marker of GFR. OBJECTIVE The objective of the study was to evaluate residual renal function among living kidney donors by comparing serum CysC concentrations and estimated GFR according to the MDRD formula or the Cockroft-Gault equation. PATIENTS AND METHODS Forty living kidney donors showed a mean age of 46.14 years. Their GFR was estimated according to the abbreviated MDRD (aMDRD) and Cockroft-Gault formula adjusted for body surface area. Twenty-two donors underwent diethylenetriaminepentaacetic acid (DTPA) renal studies. Serum CysC concentrations were measured during the last follow-up visit. GFR values according to Cockroft-Gault formula and MDRD formula were correlated with CysC concentrations using Pearson's linear correlation. RESULTS Mean GFR according to the aMDRD formula and Cocroft-Gault formula decreased after nephrectomy. The Cockroft-Gault formula overestimated the DTPA GFR in our study. No significant differences were observed between DTPA GFR and GFR estimated using the aMDRD equation. The rate of GFR decrease was approximately 0.8 mL/min/1.73 m(2) per year. No significant correlation was observed between serum CysC concentration and GFR. Microalbuminuria was observed in one patient after nephrectomy. CONCLUSIONS aMDRD equation to estimate GFR is more precise than Cockroft-Gault formula and cystatin C in living kidney donors after nephrectomy and should be preferred model in these patients.