This is a protocol for a Cochrane Review (prognosis). The objectives are as follows:

To evaluate the prognostic effect of the recipient's (i) sex and gender separately (ii) gender as an independent predictor of patient-relevant outcomes at any time period following kidney or SPK transplantation (Table 1) and explore sources of heterogeneity. We aim to evaluate this prognostic effect by (a) clearly defining the relationship between recipient sex/gender and post-transplantation outcomes, which would involve identifying reasons for variations between sexes and genders, and then (b) quantifying the magnitude of this relationship. 

Sources of heterogeneity may exist between studies that can have an impact on outcomes. We will explore potential sources, which may include patient age, self-reported ethnicity, country of transplantation, transplant era, living versus deceased donor transplantation, definitions and units used for outcomes, quality of the study, and the indication for kidney transplantation.