Does Donating a Kidney Increase Fracture Risk?

Kidney donors may have lower 1,25-dihydroxyvitamin D and phosphate levels. Their parathyroid hormone levels may be elevated, but with minimal effect on calcium levels.

Around 15,000 people who need kidneys receive one annually, with roughly one-third donated by living donors. Approximately 50,000 Americans—people who were screened carefully and in exceptional health at the time they volunteered—have donated a kidney so others can live. Most of these donors are still living. Most research indicates that there are few long-term risks in living humans donating one-half of their kidney mass. Some research has identified changes in bone mineral metabolism among living kidney donors, and potential skeletal repercussions.

Researchers from Western University, Ontario, Canada, look at the relationship between kidney donation, bone changes and fractures in a review published electronically ahead of print in Current Opinions in Urology. Until now, only one study had looked at fractures in kidney donors.

Kidney donors may have lower 1,25-dihydroxyvitamin D and phosphate levels. Their parathyroid hormone levels may be elevated, but with minimal effect on calcium levels. Some evidence indicates that fibroblast growth factor 23 concentrations rise after kidney donation, but other studies refute that finding.

Only one study (N=2015 donors and 20,150 matched non-donors) has examined the effect of vitamin D and phosphate metabolism changes in bone mineral metabolism and the risk of skeletal fracture in living kidney donors. Donors had a median age of 43 years. The researchers followed the donors and a matched cohort from the general population in good health for an average of 6.6 years (maximum 17.7 years). Donors and non-donors experienced similar fragility (osteoporotic) fracture rates.

The authors note that older studies were generally small. With increasing numbers of living kidney donors, current and future studies have larger populations to draw from and may be able to track changes more precisely. Ideally, long-term studies will be conducted to assess fracture risk in living kidney donors.