A prospective controlled study of living kidney donors: three-year follow-up

Abstract

Background: There have been few prospective controlled studies of kidney donors. Understanding the pathophysiologic effects of kidney donation is important for judging donor safety and improving our understanding of the consequences of reduced kidney function in chronic kidney disease.

Study design: Prospective, controlled, observational cohort study.

Setting & participants: 3-year follow-up of kidney donors and paired controls suitable for donation at their donor's center.

Predictor: Kidney donation.

Outcomes: Medical history, vital signs, glomerular filtration rate, and other measurements at 6, 12, 24, and 36 months after donation.

Results: At 36 months, 182 of 203 (89.7%) original donors and 173 of 201 (86.1%) original controls continue to participate in follow-up visits. The linear slope of the glomerular filtration rate measured by plasma iohexol clearance declined 0.36±7.55mL/min per year in 194 controls, but increased 1.47±5.02mL/min per year in 198 donors (P=0.005) between 6 and 36 months. Blood pressure was not different between donors and controls at any visit, and at 36 months, all 24-hour ambulatory blood pressure parameters were similar in 126 controls and 135 donors (mean systolic blood pressure, 120.0±11.2 [SD] vs 120.7±9.7mmHg [P=0.6]; mean diastolic blood pressure, 73.4±7.0 vs 74.5±6.5mmHg [P=0.2]). Mean arterial pressure nocturnal dipping was manifest in 11.2% ± 6.6% of controls and 11.3% ± 6.1% of donors (P=0.9). Urinary protein-creatinine and albumin-creatinine ratios were not increased in donors compared with controls. From 6 to 36 months postdonation, serum parathyroid hormone, uric acid, homocysteine, and potassium levels were higher, whereas hemoglobin levels were lower, in donors compared with controls.

Limitations: Possible bias resulting from an inability to select controls screened to be as healthy as donors, short follow-up duration, and dropouts.

Conclusions: Kidney donors manifest several of the findings of mild chronic kidney disease. However, at 36 months after donation, kidney function continues to improve in donors, whereas controls have expected age-related declines in function.

Keywords: Assessing Long Term Outcomes in Living Kidney Donors (ALTOLD); Chronic kidney disease (CKD); glomerular filtration rate (GFR); hemoglobin; homocysteine; kidney function; kidney transplantation; living kidney donation; mineral and bone disorders; parathyroid hormone (PTH); patient safety; potassium; renal insufficiency; unilateral nephrectomy; uric acid.

Figure 1

Measured glomerular filtration rate (GFR) in controls (solid line) and donors (dashed line) before and 6, 12, 24, and 36 months after donation. Values are means and interquartile ranges.