Background: The over-representation of females as living kidney donors (LKDs) in most countries is well documented. Medical reasons and sex-related differences - the biological and physiological features of males and females - are unlikely to be the sole drivers of this disparity. It is widely believed that these trends represent a gender disparity.
Methods: We conducted a systematic review to synthesize existing literature that had examined gender differences in motivation to pursue living kidney donation. Six electronic and two grey literature databases were searched systematically. Of the 3,188 records screened 16 empirical studies and case studies from 9 higher and 4 lower-middle income countries were included in the final analysis. Data were synthesized thematically, using the four-level social-ecological model lens.

Results: Studies were limited to two genders, tended to focus on the perspectives of women only and were predominantly descriptive. We have isolated the perspectives of 1,148 LKDs and candidates, 471 of whom were women, 290 were men, and 387 for whom gender/sex was not specified. Relationship and community factors constituted the main motivators, given that the majority of donations occurred within the family/friend network. These included overt or subtle family pressure, self-sacrifice for the well-being of the family, desire to improve recipients quality of life, beliefs in marital stability, and the differential economic status of women and men. Societal and cultural factors - gendered family roles; ethnic, religious and social norms and beliefs regarding marriageability and fertility; privileged social status of men and boys; and legislation and policy - were a cross-cutting theme influencing many elements of donation. At the individual level, LKDs exhibited strategic and deliberate decision-making. The relative importance of each factor varied based on geographical context, with more modest differences in motivation between men and women and stronger manifestation of individual factors in higher income countries. However, gender and sex were conflated in most studies, most lacked a strong methodologic approach and were at high risk of bias.
Conclusion: Despite the recognition of sex and gender disparities in living kidney donation for over three decades, our review highlights a dearth of robust evidence explaining this phenomenon. Existing evidence highlights the need to understand the complex interplay of identified factors across different cultural and geo-political contexts using a rigorous methodologic approach. This can then inform targeted policy initiatives to advance gender equity and optimally promote donation among all genders.