Effect of Obesity on Renal Function and Cardiovascular Disease Risk Factors in Long-Term Kidney Donors

Abstract

Introduction: Due to the growing demand for living donor kidneys, previously ineligible patients are being considered for donation. One increasingly used group are obese patients, and despite evidence that obesity increases risk of renal dysfunction and cardiovascular disease (CVD), the long-term consequences of kidney donation in this population remain unknown. We examined whether obese donors are at higher risk for developing renal dysfunction and other CVD risk factors years after donation. Methods: All 1750 patients who donated a kidney at our institute between 1967-2005 were contacted; of these, 219 (mean time since donation 14 7 yrs) agreed to participate. Patients were stratified according to BMI, and BP, lipid panel, serum cystatin C, and presence of Metabolic Syndrome (MS) were determined. Renal function was evaluated with direct (iohexol) as well as indirect (MDRD) Glomerular filtration rate (GFR) measurements and 24-h urine collections for total protein/albumin. Results: Clinical characteristics are listed in the Table. All BMI groups had similar age and racial distribution. There were more men and longer follow-up among obese patients (BMI 30-34.9) but this trend was seen in the entire cohort. We found no association between increasing BMI and GFR or abnormal proteinuria/albuminuria. In contrast, increasing BMI was strongly associated with increased incidence of MS, hyperlipidemia, hypertension and high serum cystatin C after donation. This was confirmed with multivariate analysis which also demonstrated that increasing BMI in female donors was associated with a higher odds ratio of developing MS (2.1 vs. 3.5), hypertension(1.7 vs. 1.5) and high serum cystatin C levels (3.4 vs. 1.3) than in men.Conclusion: On long-term follow-up, obese kidney donors are not at higher risk for renal dysfunction, but do have an increased incidence of several CVD risk factors. This finding is more pronounced among female donors. We conclude that obesity is not a contraindication to donation, but obese donors, particularly female donors, should receive systematic long-term medical follow-up.