In 1990, Barker noted, “The womb may be more important than the home” in terms of the origins of adult disease. Worldwide, every year approximately 13 to 14 million newborns (10 per 100 live births) are born prematurely and 23 million (16 per 100) weigh <2500 g (i.e., low birth weight). ^, While intrauterine growth retardation and low birth weight are invariably linked with measures of maternal poverty, much debate surrounds the influence of early fetal programming on subsequent risk of chronic diseases including those of the kidney (see Chapter 20 for a detailed discussion). The “critical periods” model is one of three models that have been proposed to explain how socioeconomic position over the life course may influence subsequent health. The “fetal programming” hypothesis is based on the critical periods model and states that intrauterine growth retardation results in permanent alterations in fetal physiology that become deleterious later in adult life. Brenner hypothesized that retardation of renal development as occurs in individuals of low birth weight increases postnatal risks for systemic and glomerular hypertension and predisposes an individual to further nephron loss and the development of progressive kidney injury. This hypothesis draws support from reports of 1. a direct relationship between birth weight and nephron number, 2. an inverse relation between birth weight and hypertension later in life, ^, and 3. an inverse relation between nephron number and blood pressure.

In addition to hypertension, low birth weight has been variably linked with risk factors such as diabetes and obesity and has been directly associated with later-life onset of microalbuminuria, reduced estimated glomerular filtration rate (eGFR), and KF. One study conducted on a cohort of term singletons born during the 1944–1945 Dutch famine found that midgestational exposure to famine was associated with microalbuminuria and that late gestational exposure was associated with glucose intolerance. Notably, a rapid increase in nephron number occurs in midgestation, which is a critical period for determining nephron endowment at birth. Moreover, rapid growth and weight gain during infancy and childhood that occur after intrauterine growth restriction (and/or low birth weight) are associated with increased risks of insulin resistance, obesity, diabetes, and hypertension. ^{, ,}

Because low birth weight is strongly linked to indices of parental poverty and occurs more commonly among socially marginalized groups, researchers have posited that low birth weight may partly account for disparities in congenital, hypertensive, and hyperfiltrative kidney diseases. ^, As noted earlier, Indigenous Australians experience higher rates of poverty and geographic isolation and an approximate 10-fold higher risk of KF than non–Indigenous Australians. Studies conducted in a remote Indigenous Australian community (where low-birth-weight infants compose approximately 25% of live births) observed that low as compared with high birth weight was significantly associated with lower kidney volumes, higher blood pressure, and later in life, lower eGFR and higher levels of urinary albumin excretion. ^, In the Bogalusa Heart Study, a biracial prospective cohort study of cardiovascular risk factors in children and adolescents in the southern United States, the prevalence of low birth weight was higher among Black than White infants. Subsequent reports have linked lower birth weight in the Bogalusa cohort with higher blood pressure levels later in life. These reports have also noted that the magnitude of the association between lower birth weight and higher blood pressure appears to increase with advancing age. ^{, ,} The trend toward increasing survival of low-birth-weight infants further underlines the importance of intrauterine fetal environment and timing of insults in future risk for developing precursors to progressive kidney disease.

Over the past 2 decades, the nephrology community has paid increasing attention to how a person’s living environment may influence downstream risk of chronic diseases. This heightened attention is evidenced by the rise in studies that examine the complex interplay of social determinants at multiple levels (individual, community, institution, society) on important processes and outcomes related to the CKD. ^, Recognition that kidney health is intricately tied to social conditions across the life course is further reflected in the Sustainable Development Goals that were adopted by the United Nations member states in 2015. People residing in underresourced neighborhoods experience more crime, less access to high-quality educational and employment opportunities, and poorer health outcomes in comparison with people from less distressed areas. ^, In fact, the Black Lives Matter Movement formed to build local community power in direct response to systematic violence inflicted on, and social inequities suffered by, Black communities.

Several contemporary studies have described higher incidence of KF, as well as higher prevalence of albuminuria and reduced eGFR in areas of high (versus low) residential poverty. ^{, , ,} However, debate continues around how and how much adverse social conditions influence a person’s subsequent risk of developing chronic diseases of the kidney. Social conditions act through a host of intermediaries such as education, housing, and diet, thereby molding health-related behaviors, which in turn influence risk for kidney disease. ^{, ,} Prior studies suggest that education may influence disparities in health behaviors through its effects on lifestyle, social support, and social norms, whereas income may drive disparities in health outcomes through access to resources and services including health care. ^, The social distribution of important risk factors for progressive kidney disease including the higher prevalence of smoking, low birth weight, type 2 diabetes mellitus, hypertension, and obesity within poor as compared with less impoverished areas, lends evidence to these claims. ^, This unequal distribution of intermediary exposures linked to progressive kidney injury is further compounded by the vulnerability of certain groups (e.g., persons of low socioeconomic position, rural/remote-dwelling residents, and members of minoritized race and ethnic groups) to health-compromising illnesses such as KF. Poor health then exerts potent feedback on an individual’s socioeconomic position through lost income or medical costs associated with a major illness (see Fig. 81.1 ). Recent studies have focused on increasing screening for individual-level social risks and health-related social needs. These studies have highlighted potential flaws in using area-level structural measures for individual-level social risks as they are commonly incongruent (e.g., not all individuals in a community that lacks safe and affordable housing experience unsafe housing or homelessness).

The concept of “allostatic load,” the accumulation of physiologic insults due to repeated insults or chronic stressors experienced in daily life, has gained increasing interest as a model for explaining socioeconomic, geographic, and race and ethnic disparities in care processes and outcomes of chronic diseases. ^, Specific measures of allostatic load include levels of hormones secreted in response to stress and biomarkers that reflect the effects of these hormones on the body. ^, This concept, which is based on the cumulative exposures theory, posits that stress may accumulate from early life and manifest as an accumulation of physiologic dysregulation. ^, Chronic stressors such as food insecurity, discrimination, living in substandard housing, inadequate access to health care, and exposure to violence are more pronounced among persons of lower socioeconomic status than among those of intermediate or higher socioeconomic status. ^, Such psychosocial stressors may lead to hypertension and autonomic dysregulation (e.g., diminished heart rate variability), which in turn are linked to increased risk of incident KF. ^{, ,} Accordingly, higher levels of exposure and adaptation to life stressors experienced more commonly by the poor or members of some minoritized groups may put them at higher risk for kidney disease through the aforementioned pathways than their less impoverished or referent majority counterparts.

Similarly, contemporary debates in many high-income countries have increasingly focused on the role of nutrition and childhood obesity in later-life risks for development of chronic disease. ^, Estimates suggest that more than a third of children in North America and Europe and approximately a quarter in the western Pacific and southeast Asia are overweight or obese and that the prevalence of childhood obesity is higher among minoritized (vs. majority) groups. Public health policy and nutrition experts attribute the marked growth in childhood obesity to the widespread availability of energy-dense, inexpensive foods and the low energy requirements of modern daily life. Studies have also linked residence in impoverished areas with higher levels of processed food consumption (rich in sodium and phosphorus), lower levels of physical activity, and increased risk for chronic diseases such as cardiovascular disease, diabetes, and hypertension in comparison with residence in more affluent areas. ^{, ,} In addition to offering fewer options for affordable, nutritious foods, poorer neighborhoods tend to have fewer (or less attractive) areas to promote physical activity such as parks and community centers. ^, The undue influence of crime, poor housing quality, and suboptimal educational and medical infrastructure may also render poor communities less supportive of healthy lifestyles than less distressed neighborhoods. One study linked race and ethnic disparities in childhood obesity with differential exposure to risk factors during early life, such as gestational diabetes, rapid infant weight gain, excessive television viewing, and high intake of sugar-sweetened beverages or fast food. The strong relation between childhood obesity and later-life antecedents of hypertensive and hyperfiltrative kidney diseases (adult obesity, hypertension, metabolic syndrome, type 2 diabetes mellitus) suggests that interventions that target the early life period may contribute substantially to reducing socioeconomic, geographic, and race and ethnic disparities in kidney and other chronic diseases. ^{, ,}

Perhaps the strongest evidence that neighborhood resources influence downstream risk factors and lead to health status disparities in kidney disease emanates from the Moving to Opportunity Study. ^, During 1994–1998, the U.S. Department of Housing and Urban Development conducted a “randomized social experiment” in five cities (Baltimore, Boston, Chicago, Los Angeles, and New York City) to examine the extent to which relocating from a more to a less distressed neighborhood might influence downstream health outcomes. Collectively, 4498 women (90% were either Black or Hispanic women) with children from high-poverty neighborhoods were randomly assigned to one of three groups: 1788 were assigned to receive housing vouchers that were redeemable only if they relocated to a low-poverty area, 1312 received unrestricted vouchers, and 1398 were assigned to a control group that offered neither of these opportunities. In terms of risk factors for kidney diseases, the study found that participants who received a voucher to relocate to a low-poverty neighborhood experienced absolute risk reductions of 5% and 4% for extreme obesity and diabetes mellitus, respectively, 10 to 15 years later in comparison with controls. Notably, the effects of relocation occurred without detectable effects on individual-level income. However, the strong correlation between neighborhood characteristics (e.g., crime, educational and employment opportunities, recreation, and social norms) makes the evaluation of specific pathways to these outcomes elusive. Although provocative, the results of the Moving to Opportunity Study highlight the challenges faced by policy makers and clinicians in addressing the legacy of structural racism and more proximal mediators of disparities in important CKD risk factors.

Regrettably, in many parts of the world, structural discrimination and systemic bias have resulted in inequitable living environments frequently based on race or ethnicity. Link and Phelan emphasize that race is itself so closely tied to social and economic resources that it should also be considered a fundamental cause of health inequality. Claims that social disadvantage largely explains disparities in risk for progressive kidney diseases among marginalized groups, for example, are supported by several studies. Among 603 children (median age 10 years) with nonglomerular kidney diseases enrolled in the CKD in Children study, the significantly shorter time to KF onset among Black as compared with non-Black children (median difference 3.2 years) was attributable to indices of socioeconomic status. In adults, nearly three-quarters of the excess risk of incident albuminuria or reduced eGFR among Black in comparison with White participants in the Atherosclerosis Risk in Communities Study was likewise attributable to measures of socioeconomic status and health care access. ^, However, studies in other health care settings indicate that a substantial fraction of the excess risk of incident KF among Black and White Americans remains unexplained even after one has accounted for differences in the distribution of KF risk factors, measures of socioeconomic status, and access to health care. The persistence of marked racial disparities in KF risk within settings where socioeconomic gradients are theoretically reduced, along with contemporary genetic data (see later) linking West African ancestry to certain forms of progressive kidney disease, further highlights the complex influences of gene–environment interactions on these disparities.

Our understanding of disparities in kidney diseases among other minoritized race and ethnic groups is less developed, but the origins of these disparities share common social constructs. In North America, for example, the incidence of KF is substantially higher among Indigenous Americans (primarily among American Indians and Indigenous Canadians) than among non–Indigenous Americans. ^{, , ,} This situation is mirrored in the Indigenous people of Australia and New Zealand who frequently reside in rural or remote communities. Differences in the distribution of major CKD risk factors, such as obesity, diabetes mellitus, and hypertension, account for most of this excess risk of KF among indigenous people. ^{, ,} In fact, long-term cohort studies of Indigenous Australians suggest that the lifetime risk of KF among people with diabetes may be as high as 41% in this group. Moreover, the remote location of many indigenous communities combined with cultural differences in their understanding of illness often hinders the implementation of interventions to adequately address CKD risk factors. ^{, , , ,} Notably, the U.S. Indian Health Services began systematic efforts in the 1990s to identify, screen for, and address risk factors—primarily blood pressure and diabetes control—among American Indians ( Fig. 81.2 ). These efforts have been widely touted as the drivers of the decline in the incidence of diabetes-related KF among American Indians over the ensuing 3 decades ( Fig. 81.3 ). ^{, ,}

Risk factor control among American Indians with diabetes mellitus within the U.S. Indian Health Service.

From Bullock A, Burrows NR, Narva AS, et al. Vital signs: decrease in incidence of diabetes-related end-stage renal disease among American Indians/Alaska Natives—United States, 1996–2013. MMWR Morb Mortal Wkly Rep . 2017;66(1):26–32.

Trends in age- and sex-adjusted incidence rate (per million/year) of end-stage kidney failure by race and ethnicity in the United States, 2000–2020.

From Johansen KL, Chertow GM, Gilbertson DT, et al. U.S. renal data system 2022 annual data report: epidemiology of kidney disease in the United States. Am J Kidney Dis. 2023;81(3S1):A8–A11.

In 1971, Julian Tudor Hart observed in his landmark paper “The Inverse Care Law” that disadvantaged populations needed more health care than advantaged populations but received far less. Disparities in the surveillance and treatment of CKD risk factors likely contribute to the higher incidence of more advanced CKD in marginalized populations. Persons with CKD from underresourced communities are often difficult to identify because few countries (including those with high per capita health care spending) track the care of poor or uninsured patients. ^{, , ,} In many instances, CKD can be slowed or prevented. Interventions such as blood pressure lowering, use of inhibitors of the renin–angiotensin system and sodium-glucose transporter-2, and avoidance of nephrotoxins are effective in reducing morbidity and slowing progression of most kidney diseases. However, differences in health system access (e.g., according to socioeconomic position) limit the time and resources needed to effectively implement these interventions in the target populations, as evidenced by underutilization of these therapies among marginalized groups.

In countries without universal health care, such as the United States, the scope of basic health insurance coverage plays a critical role in the treatment of modifiable risk factors for kidney diseases. The presence and scope of basic health insurance is also linked to pre-KF nephrology care, mortality, and preparedness for KF (i.e., rates of home dialysis usage, kidney transplantation, and hospitalization and venous catheter usage at dialysis initiation). ^, For example, Kurella-Tamura and colleagues observed a significantly lower incidence of KF and smaller health insurance–related gaps in pre-KF nephrology care access among states with broader as compared with narrower health insurance coverage for the poor. In 2014, USA policymakers and health care providers heralded expansion of basic health insurance coverage for low-income people in the United States under the Affordable Care Act. In terms of pre-KF nephrology care access, states that expanded coverage under the Affordable Care Act witnessed 59% more preemptive listings for kidney transplantation among low-income people than states that did not expand coverage. There were also proportionately larger increases in basic health insurance coverage among preemptively listed people of minoritized race and ethnic groups as compared with those of non-Hispanic White race.

As noted earlier, prior studies showed that lack of health insurance coverage, residential poverty, and non-White race or ethnicity were independently associated with worse metabolic abnormalities at dialysis initiation, including more severe hypoalbuminemia, azotemia, and anemia, and with marked delays in accessing the transplant waiting list and in receiving a kidney transplant. ^{, ,} The previously mentioned reports suggest that marginalized groups receive less and perhaps substandard care in earlier stages of CKD. ^, Although differences in individual-level factors such as adherence to screening and treatment recommendations may partly contribute to these disparities, it is likely that differential access to the health system plays a central role in determining which groups receive these interventions, particularly at earlier stages of CKD. However, as Schrag noted in 1983, the ability to pay for health services does not necessarily guarantee their availability. Differential access to health services is also well documented within high-income countries with universal health care, such as in the United Kingdom, where the age- and sex-adjusted prevalence of severe CKD (eGFR <30 mL/min per 1.73 m ² at presentation) was 6- to 9-fold higher in areas of Sheffield with the highest (vs. lowest) deprivation. The higher risk of severe CKD in impoverished areas was largely attributable to differences in the distribution of diabetes and hypertension. ^,

The medical care of most marginalized groups is concentrated in the hands of relatively few providers. For example, owing to their relatively limited options for ongoing ambulatory care, many marginalized people (low-income, underinsured, members of minoritized race and ethnic groups, refugees, homeless, and those with specialized care needs such as addiction medicine and mental health) in the United States seek ambulatory care from public hospitals and safety net health care clinics. ^, Even within universal health care systems such as in Canada or Australia, the rural or remote nature of some minoritized communities strongly influences the availability, frequency, and quality of care received. ^{, ,} The centralization of services that disadvantage rural and remote patients is especially apparent in transplantation, where most specialists and transplant centers are located in large urban centers. Several studies demonstrated that socioeconomic, geographic, and race and ethnic disparities in care may be partly explained by differences in where and by whom patients are treated, leading to systematic differences in the care environment, provider quality, and access to care. ^{, ,} For example, Bach and associates found that Black and White Medicare beneficiaries were treated for the most part by different primary care physicians. Moreover, the primary care physicians who cared primarily for Black patients were less likely to be board certified, more likely to be in training, and more likely to report encountering system barriers to providing high-quality care to their patients (e.g., securing referrals to specialists). Varkey and colleagues further found that clinics serving higher proportions of patients from minoritized race and ethnic groups were more chaotic than, and had different organizational characteristics from, those of private clinics.

Recent qualitative studies of nephrology and primary care providers have identified system–level factors such as referral process delays, insufficient time to build patient partnerships, and poorly integrated nephrology and primary care as major barriers to optimal preparation for KF in diverse health care settings. ^, Such systematic barriers may also account for the historically lower utilization of home dialysis and preemptive kidney transplantation among Black, Hispanic, and rural-dwelling patients than among non-Hispanic White and urban-dwelling patients, respectively. ^, In short, several key factors linked to the provision of high-quality medical care, such as coordination of care, subspecialist access, and provider experience differ markedly according to the health system. Such health system–level determinants may delay or restrict the access of marginalized patients to receiving adequate prevention and management of kidney disease and its antecedent risk factors.

People from rural/remote communities commence their journey with CKD from a disadvantaged position because they tend to have fewer economic resources, less formal education, and lower access to primary and specialist health care than people from urban communities. They face many barriers to access kidney replacement therapies, including late referrals to specialist nephrologist care, forced relocation to access treatment, transportation challenges, and financial hardship ( Table 81.1 ). These factors often intersect and contribute to an increased risk of mortality, morbidity, and hospitalization compared with their urban counterparts. ^, For patients on maintenance dialysis, longer travel time to dialysis (>50 km) is associated with higher mortality, higher and earlier risk of peritonitis for people on peritoneal dialysis, and decreased quality of life. Rural and remote-dwelling patients encounter far more barriers to accessing kidney transplantation due to the highly centralized nature of specialist care and transplant centers, which are universally located in large cities. Logistic barriers range from costly transportation and housing to the cultural impacts of relocation and isolation. Among patients with advanced kidney disease, rates of relocation (for care) increase with higher degrees of residential remoteness: Low prevalence of in-center hemodialysis facilities in remote areas is a primary driver of this medical relocation. The adverse effects of permanent or medical relocation for rural and remote-dwelling patients and their families can be particularly challenging for Indigenous People of Canada and Australia (see Table 81.1 ). ^, These effects include cultural isolation, feeling homesick, separation from family and friends, and psychosocial stress, which can further impact health outcomes.

In terms of survival and quality of life, kidney transplantation remains the optimal treatment for most patients who progress to KF. However, significant disparities in receiving a transplant according to socioeconomic status, geography, race, and ethnicity persist worldwide. ^{, , ,} In Canada, transplantation rates among Aboriginal, African, Indo Asian, and East Asian Canadians range one-half to two-thirds those of White Canadians despite the presence of uniform health insurance coverage. ^, In Australia, transplantation rates in Indigenous Australians are 77% lower than those in nonindigenous Australians, and in New Zealand, Maori and Torres Strait Islander patients with KF are similarly disadvantaged. Similar disparities are also present in the United States, where kidney transplantation rates are significantly lower among the poor and among patients of most minoritized race and ethnic groups than among less disadvantaged groups and non-Hispanic White patients, respectively. ^,

Although key mediators of, and their relative contributions to, health disparities in transplant access vary by population and health system, many are directly linked to structural discrimination (e.g., forced displacement) and the social conditions described previously. ^, For example, in the United States, geographic differences account for most of the disparity in receiving a deceased-donor kidney from the waiting list among Hispanic, Native Hawaiian, Pacific Islander, American Indian, and Alaska Native patients. By contrast, contextual poverty and health insurance coverage account for the largest fraction of the disparity in live-donor kidney transplantations among American Indian, Alaska Native, and Black and Hispanic patients in comparison with non-Hispanic White patients. Additional studies have identified differences in attitudes and knowledge about kidney transplantation among Black and Hispanic Americans in comparison with non-Hispanic White Americans. In Australia, only 1.9% of Indigenous patients receiving maintenance dialysis were actively listed as compared with 9.5% of non-Indigenous dialysis patients. ^, A study of kidney specialists reported that concerns about poorer outcomes for Indigenous Australian patients compared with non-Indigenous patients was a major reason for nonreferral (for transplant waitlisting). The influence of geographic, cultural, and/or linguistic isolation on delays in accessing the transplant waiting list or receiving a kidney transplant remains understudied.

Marginalized patients appear to encounter more difficulty in navigating the complex steps required to successfully receive a kidney transplant, and this vulnerability appears to have changed little over time. This may be a direct effect of low health literacy, inadequate insurance coverage, suboptimal patient–provider communication, and lack of support and information about transplant, all of which have been linked to delays in accessing the transplant waiting list, in completing the transplant evaluation, and in successful receipt of a transplant. ^{, , ,} As noted earlier, kidney providers also appear reticent to refer marginalized patients for transplant because of concerns about poor outcomes or inadequate coverage for prescription and procedural costs. ^{, ,} In a national survey of transplant programs in the United States, >70% responded that they frequently or occasionally exclude patients from the kidney transplant waitlist owing to concerns that the patients will not be able to afford the immunosuppressive medications.

Although socioeconomic status and contextual poverty are linked with disparities in transplantation rates in the United States, ^{, ,} the magnitude of such disparities is markedly higher in middle-income nations such as in Mexico, where transplantation rates are more than 10-fold higher among insured patients than among uninsured patients. As concerning is the unethical practice of organ trafficking and exploitation of disadvantaged populations for profit that occurs in many low- and middle-income nations. This pervasive commercialization of live-donor transplantation is supported by reports of affluent foreigners undergoing large fractions of the kidney transplantations performed in some low- and middle-income countries. Although some writers justify paying persons to donate a kidney as mutually benefiting recipient and donor, one study conducted in India showed that such transactions do not lead to long-term economic benefit and may be associated with a decline in health for the donor.

Socioeconomic, geographic, and race and ethnic disparities in kidney transplantation extend to outcomes after receipt of a functional allograft. Similar to transplant access, specific causes of these disparities in allograft survival may differ by population and health system, but the root causes commonly reflect differential social conditions and access to high-quality health care. For example, adherence to posttransplantation immunosuppressive therapy remains a critical determinant of long-term allograft survival. Regrettably, inability to afford immunosuppressive medications appears to be a primary mechanism that restricts low-income patients from not only receiving a kidney transplant but also maintaining one. ^, In one study, >40% of transplant recipients reported financial difficulty after transplantation, with health-related out-of-pocket expenses averaging approximately US$475 per month. In a recent single-center study of 1171 kidney transplant recipients, lower socioeconomic status was associated with an 11% higher risk of acute rejection and 77% higher risk of graft loss among Black versus non-Hispanic White Americans. Socioeconomic disparities in maintaining a transplant are magnified in medium-income countries such as Mexico and Pakistan, where excellent long-term results for allograft survival are offset by the prohibitive cost of immunosuppressive and antiviral medications. In these countries, transplant access and allograft maintenance for the average citizen often require a state-sponsored model. ^{, ,}

Racial differences in biologic factors such as age at transplantation, HLA mismatching, and APOL1 genotype status may account to some degree for the remaining disparity in allograft survival between some race and ethnic groups, such as between Black and White Americans. ^{, ,} The transplant community is now seeking ways to integrate the APOL1 genotype into clinical practice to enhance evaluation of donor organs and better align this assessment with recipient needs. Although prevailing beliefs attribute reduced graft survival among Black recipients to heightened immune responsiveness and poorer immunologic matching, few reports have actually linked better HLA matching with improved graft survival in this race group. ^{, ,} Moreover, Asian recipients enjoy the longest graft survival of all race and ethnic groups despite the presence of suboptimal HLA matching comparable with that observed in Black recipients. ^, Irrespective, the influence of biologic perpetrators of race and ethnic disparities in kidney transplantation access, such as the distribution of ABO blood type and HLA, has progressively declined in the United States due to advances in the deceased-donor allocation policy. ^{, ,}

Lastly, studies have raised concerns regarding inequities in the quality of transplanted organs based on recipient socioeconomic status and race and ethnicity. Data on provision of comparatively “lower-quality organs” to recipients from marginalized groups than to White, more affluent, or college-educated counterparts have cast additional light on the complex nuances that underlie this social gap in allograft access and survival. ^, In terms of the disparity in allograft loss between Black and White Americans, the gap has steadily declined over the past 2 decades. Recent data from the U.S. organ transplant registry point to differential improvements in 5-year graft survival after deceased-donor kidney transplantation among Black (from 49% to 69%) as compared with White (from 63% to 75%) Americans. Similar gains (63% to 79% among Black vs. 79% to 86% among White patients) have led to a narrowing of the Black–White gap in allograft survival following living-donor kidney transplantation in the United States. Temporal changes in deceased-donor allocation, immunosuppressive agents, and desensitization strategies have been credited as major contributors to these observations.