A new study by researchers at University Hospital Basel suggests that the success of a kidney transplant may depend on gender. More exactly, women who receive kidneys from males have a higher rate of graft failure than other donor-recipient combinations.

For the study, the researchers from the Collaborative Transplant Study in Heidelberg led by Professor Alois Gratwohl from University Hospital Basel, Switzerland) analyzed data on 195,516 people in Europe who received kidneys from deceased donors between 1985 and 2004 at over 400 centers in Europe and, surprisingly, found complex gender interactions.

To be more specific, after 1 to 10 years, recipients of female kidneys were more likely to experience graft loss than recipients of male kidneys. Generally, male recipients were more likely to experience graft failure between years 1 and 10 compared to female recipients.

One significant difference was seen in the transplantation of male kidneys into female kidney. In this situation, the risk of failure in the first year was 11 percent higher than average, and 8 percent more likely overall.

Therefore, the researchers suggested that “consideration of sex should be integrated into future prospective analyses and decisions on organ allocation.”

Male kidneys are larger and have a higher number of nephrons (the basic structural and functional unit of the kidneys), which make them fit more into a male recipient. On the other hand, women may not need as many nephrons and could benefit from female kidneys.

Conclusively, the researchers suggest that doctors should consider more “same-sex” transplants, as they have more chances of success than any other donor-recipient combination.

The findings were welcomed by Dr. Connie Davis, from the University of Washington in Seattle, who, in accompanying editorial, wrote that “H-Y antigens can no longer be ignored in the setting of solid-organ transplantation.” However, shortage of suitable organs doesn’t allow doctors to always choose “same-sex” transplants.

On the other hand, a spokesperson for UK Transplant quoted by the BBC said “no statistical evidence was found to suggest any of the sex-related factors significantly affected post-transplant graft survival. Therefore, donor to recipient sex matching is not something that is considered in the kidney allocation scheme.”

The findings of the study were published in this week’s edition of The Lancet.