Women receiving kidneys from males donors are at a higher risk of organ rejection than those who received one from another woman, a new Swiss study says. Researchers now recommend that the gender of patients and donors should be considered in future operations to avoid such problems.

Researchers at University Hospital Basel analyzed data on 195,516 people in Europe who received kidneys from deceased donors between 1985 and 2004, and found that gender can substantially affect whether the operation will be successful.

The study, which was published in this week's issue of The Lancet, also noted that male recipients may benefit from bigger male kidneys as it has the higher number of nephrons, which are the basic structural and functional units of the kidney.

The increased risk of failure when women receive a male kidney could be the effect of a specific male chromosome which produces a reaction which can cause the kidney to be rejected by a woman's immune system.

Failure can lead to death or years of dialysis while a patient waits for another kidney to be found. Kidney transplantation or renal transplantation is the organ transplant of a kidney in a patient with end-stage renal disease.