A study of renal outcomes in obese living kidney donors.

Background: Little is known about the long-term outcomes of obese living kidney donors (OLKDs). We undertook this study to describe renal outcomes of OLKDs several years after donation.
Methods: We invited 101 OLKDs for follow-up health evaluation.
Results: Thirty-six subjects (35.6%) completed evaluation at 6.8±1.5 years postdonation. The mean estimated glomerular filtration rate (eGFR) using the abbreviated modification of diet in renal disease (MDRD) equation (MDRD-eGFR) at follow-up was 72.1±16.3 (range: 42-106) mL/min per 1.73 m, and 47.2% of subjects had an MDRD-eGFR of 30 to 59. The absolute decrease in MDRD-eGFR from the time of donation to follow-up was 27.2 ± 13.1 mL/min per 1.73 m (P<0.001 on paired t test), which represents a 29.2% drop in the serial MDRD-eGFRs. Seven subjects (19.4%) had microalbuminuria (30-300 μg/mg creatinine). Subjects with microabuminuria were more likely to have MDRD-eGFR of less than 60 mL/min per 1.73 m (P=0.021). Subjects whose body mass index was greater than or equal to 35 kg/m (n=14) were found to have an absolute decrement in MDRD-eGFR similar to those with body mass index less than 35 kg/m (31.5 ± 15.6 and 24.7 ± 11.0 mL/min/1.73 m, respectively; P=not significant). Fifteen (41.6%) were hypertensive at follow-up.
Conclusions: On medium-term follow-up, a large proportion of OLKDs will have a MDRD-eGFR of less than 60 mL/min per 1.73 m, and the likelihood increases markedly among those who develop microalbuninuria. This raises concern for hyperfiltration injury. Furthermore, OLKDs experience a substantial incidence of hypertension. Caution is advised in selecting OLKDs pending further data on long-term outcomes.