The impact of donor and recipient gender combination on kidney transplant outcomes has been reported in several studies. The results vary greatly due to different factors, such as minor histocompatibility antigens, nephron overload, sex hormones, etc. Despite advancements in clinical practice, no large-scale studies exploring this question in living donor kidney transplantation have been conducted in the subsequent two decades. Our study aims to address this research gap and provide updated information on outcomes in relation to the gender combination following living donor kidney transplantation.

The impact of donor and recipient gender combination on kidney transplant outcomes has been reported in several studies, but with inconclusive results. From an immunologic perspective, the transplantation of male donor kidneys into female recipients was associated with an increased risk of graft failure and mortality due to H-Y minor histocompatibility antigens. Another theory, based on nephron overload and hyperfiltration, suggests that male recipients of female donor kidneys tend to experience worse outcomes due to the smaller size of female kidneys. Additionally, the influence of sex hormones has been explored. Aufhauser et al. found that estrogen acts as a protective factor against ischemia-reperfusion injury (IRI), resulting in a significantly lower incidence of delayed graft function (DGF) in female recipients compared to male recipients. These findings seem conflicting, and most of studies have primarily focused on deceased donor kidney transplantation.

In addition, Kayler et al. analyzed a transplant database encompassing 30,258 living donor kidney transplantations between 1990 and 1999. Their study revealed a significant advantage in graft survival for male recipients of male donor kidneys compared to the other combinations. Another study involving 5,716 HLA-identical sibling kidney transplantations between 1985 and 2000 demonstrated that female recipients tend to have better graft survival rates regardless of the donor's gender. Despite advancements in clinical practice, no such large-scale studies exploring this question have been conducted in the subsequent two decades. Our study aims to address this research gap and provide updated information on outcomes in relation to the gender combination following living donor kidney transplantation.

Inclusion Criteria:

• Patients undergoing living donor kidney transplantation in the Erasmus Medical Center between January 2010 and December 2020.

Exclusion Criteria:

• Recipients who were under 18 years at transplant or had no follow-up.

Participant eligibility is based on biological gender.

Patients undergoing living donor kidney transplantation in the Erasmus Medical Center between January 2010 and December 2020.

The data that support this study are not publicly available due to the reasons of sensitivity and are available from the corresponding author upon reasonable request.