FRIDAY, July 4 (HealthDay News) -- Women who receive kidneys from males have a higher rate of graft failure than other donor-recipient combinations, and gender should be considered when choosing donor matches, a new Swiss study says.

Researchers at University Hospital Basel analyzed data on 195,516 people in Europe who received kidneys from deceased donors between 1985 and 2004, and identified complex gender interactions. Graft loss was more common with kidneys from female donors than with kidneys from male donors after both one year and 10 years. Female recipients had a lower rate of graft failure between the end of the first year and the end of the 10th year.

Compared with all other gender combinations, transplantation of male donor kidneys into female patients was associated with an 8 percent increased risk of graft failure and an 11 percent increased risk of graft failure-related death in the first year. Between two and 10 years, the rates were 6 percent and 10 percent.

"Our multi-variable analysis showed that transplantation of kidneys from male donor into female recipients caused an increased rate of graft failure, which suggests an immunological H-Y effect in renal transplantation during the first year after transplantation that extends to 10 years of follow-up ... Consideration of sex should be integrated into future prospective analyses and decisions on organ allocation," the researchers wrote.

They noted that male recipients may benefit from bigger male kidneys, with their higher number of nephrons, which are the basic structural and functional units of the kidney. Women may not need the same number of nephrons as men, and could benefit from the lower likelihood of rejection associated with a kidney from a female donor.

The study was published in this week's issue of The Lancet.

"H-Y antigens can no longer be ignored in the setting of solid-organ transplantation. A lot of work still needs to be done on the actual antigens and the immunological responses that might be associated with rejection. However, the science is still too premature to suggest that allocation schemes from dead donors or selection of living donors for transplantation take notice of this effect, in view of the good long-term success with sex-mismatched allografts and the limited access to organs," Dr. Connie L Davis, from the division of nephrology and transplantation at the University of Washington, Seattle, wrote in an accompanying comment.

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