Prior research has supported the safety of kidney donation and that donation has no effect on survival or function of the remaining kidney, lead author Dr Hassan N Ibrahim, from the University of Minnesota, Minneapolis, and colleagues explain. Still, most studies examining this topic have had relatively small sample sizes with only limited follow-up.

To examine long-term safety of kidney donation, Ibrahim's team analyzed data for 3,698 individuals who donated kidneys from 1963 to 2007. In 255 donors whose surgery was performed in 2003 or later, the researchers assessed the glomerular filtration rate (GFR), albuminuria, hypertension, general health status, and quality of life.

GFR is a measure of kidney function as expressed as the amount of blood filtered through the kidneys per minute, sometimes referred to as creatinine clearance. The normal range is typically 90 to 120 millilitres per minute (mL/min). Rates below 60 mL/min suggest kidney dysfunction and rates below 15 mL/min indicate kidney failure. Albuminuria, or albumin in the urine, is also an indication of kidney dysfunction.

No significant difference in survival was noted between donors and age-matched controls, the report indicates. Moreover, end-stage kidney disease was actually more common in controls than in donors: 268 vs. 180 cases per million per year.

During an average follow-up period of 12.2 years, 85.5 percent of the subjects in a subgroup analysis had a GFR of at least 60 mL/min/1.73 m of body-surface area. Hypertension and albuminuria were seen in 32.1 percent and 12.7 percent of subjects, respectively.

Older age and higher body mass index were predictive of hypertension and a reduced GFR on long-term follow-up. By contrast, a longer time since donation did not correlate with reduced GFR or hypertension, although it was linked with a decrease in albuminuria.

Quality of life was not adversely affected by donation and, in fact, donors usually had scores that were better than those in the general population. Having more than one illness occurred with comparable frequency in the donor and general populations.