Background: we evaluated the impact of combined age of living donor and recipient on kidney transplant outcome.

Methods: Retrospective cohort study on 3068 kidney transplant recipients at Mansoura Urology and Nephrology Centre between March 1976 and December 2019, divided into four groups according to age, group I: recipients < 40 years from donors < 40 years (1665 KTrs), group II: recipients < 40 years from donors ≥ 40 years (932 KTrs), group III: recipients ≥ 40 years from donors < 40 years (320 KTrs) and group IV: recipients ≥40 years from donors ≥ 40 years (151 KTrs).

Results: Incidence of rejection was higher in group I and lower in group VI. Incidence of post-transplant hypertension, diabetes, hepatic impairment and malignancy was higher in group III and lower in group II (p value: 0.0001). Overall, 5, 10 and 15 years graft survival was better in group IV and worse in group II (p value: 0.013). 5, 10 and 15 years' patient survival was better in group II and worse in group III (p value: 0.0001).

Conclusions: Young donor to young recipient transplantation was associated with higher incidence of rejection. Old donor to young recipient transplantation was associated with the best patient survival, lower incidence of post-transplant medical complications but the worst graft survival. Young donor to old recipient transplantation was associated with higher incidence of post-transplant medical complications and worst patient survival. Old donor to old recipient transplantation was associated with the lowest incidence of rejection and the best graft survival.