Obesity as a barrier to kidney transplantation: Time to eliminate the body weight bias?

Engineering Equity Into the Promise of Xenotransplantation

Two of the greatest challenges facing kidney transplantation are the lack of donated organs and inequities in who receives a transplant. Xenotransplantation holds promise as a treatment approach that could solve the supply problem. Major advances in gene-editing procedures have enabled several companies to raise genetically engineered pigs for organ donation. These porcine organs lack antigens and have other modifications that should reduce the probability of immunological rejection when transplanted into humans. The US Food and Drug Administration and transplantation leaders are starting to chart a path to test xenotransplants in clinical trials and later integrate them into routine clinical care. Here we provide a framework that industry, regulatory authorities, payers, transplantation professionals, and patient groups can implement to promote equity during every stage in this process. We also call for immediate action. Companies developing xenotransplant technology should assemble patient advocacy boards to bring the concerns of individuals with end-stage kidney disease to the forefront. For trials, xenotransplantation companies should partner with transplant programs with substantial patient populations of racial and ethnic minority groups and that have reciprocal relationships with those communities. Those companies and transplant programs should reach out now to those communities to inform them about xenotransplantation and try to address their concerns. These actions have the potential to make these communities full partners in the promise of xenotransplantation.

Bariatric Surgery as a Bridge to Facilitate Renal Transplantation in Patients with End-Stage Renal Disease

PURPOSE

Renal transplantation (RT) is not recommended above BMI 40 kg/m2 as post-operative risks (delayed graft function, wound complications) are increased. Bariatric surgery (BS) results in sustained long-term weight loss. However, renal failure (RF) patients are theoretically higher risk candidates. We aim to investigate the safety of BS in patients with RF and the effect of BS on access to renal transplantation.

METHODS

We reviewed data from 31 patients with RF referred for BS between 2013 and 2021. We compared the outcomes of patients with RF who underwent BS to those who were referred but did not undergo BS. Controls matched for age/BMI/comorbidity (MC) but without RF were used for comparison.

RESULTS

Of 31 patients referred, 19 proceeded with BS (68% female, median age 52 years, BMI 46.2 ± 4.9 kg/m2) and 12 did not (58% female, median age 58, mean BMI 41.5 ± 4.1). Excess body weight loss (EBWL) was 71.2% ± 20.2% at 2 years in RF patients versus 66.0% ± 28.0% in MC patients. In the operated group, 11/19 (58%) patients reached their treatment target (six transplanted, five placed on waiting list) versus 3/12 (25%) in unoperated patients (three transplanted). There was no difference in perioperative complications between RF and MC groups. Long-term, there were seven deaths amongst RF patients (two operated, five unoperated), none amongst the MC group.

CONCLUSION

BS in patients with RF increased access to RT and was safe and effective. We therefore recommend consideration of BS in patients with obesity and RF in specialised units.

Bariatric surgery improves access to renal transplantation and is safe in renal failure as well as after transplantation: A systematic review and meta-analysis

INTRODUCTION

Effective workup and listing of end-stage renal disease (ESRD) patients for renal transplantation, often with multiple co-morbidities, poses a challenge for transplant teams. Obesity is a common co-morbidity associated with adverse outcomes in ESRD and kidney transplant (KT) recipients. Bariatric and metabolic surgery (BMS) has long been established as a safe and effective treatment for morbid obesity. In this study, the authors aimed to evaluate the strength of evidence for both the efficacy and safety of bariatric surgery in patients with ESRD or kidney transplantation.

METHODS

A literature search was performed using key terms including "transplantation", "kidney", "renal", "obesity", and "bariatric". Databases searched include MEDLINE, EMBASE and Web of Science from inception to date (April 2021). Methodological quality was assessed using the Newcastle-Ottawa tool. Selected articles were then categorised into patients awaiting waiting list acceptance, patients awaiting transplantation, patients undergoing simultaneous BMS + KT and patients undergoing BMS following a previous renal transplant. Summary effects are presented with a level of statistical significance and 95% Confidence Intervals.

RESULTS

A total of 28 articles were selected following the literature search. Fourteen studies on patients awaiting listing (n = 1903), nine on patients on the KT waiting list (n = 196), a single study on simultaneous BMS and KT and ten studies on patients undergoing BMS following KT (n = 198). Mean change in BMI for patients awaiting listing was -11.3 kg/m² (95%CI: -15.3 to -7.3, p < 0.001), mean change in BMI for patients listed for KT was -11.2 kg/m 2(95%CI: -12.9 to -9.5, p 0.001) and mean change for patients with prior KT was -11.0 kg/m² (95%CI: -7.09 to -14.9, p < 0.001). The combined mortality rate for patients who had undergone both BMS and KT was 4% (n = 15).

DISCUSSION

This review demonstrates BMS is both safe and efficacious in patients with ESRD prior to KT and in those post KT. It would enable difficult-to-list obese recipients the possibility to undergo transplantation and should be considered as part of the work up process.

The Fat Kidney

PURPOSE OF REVIEW

The purpose of this review is to summarize the current evidence on the role of obesity in the development and progression of chronic kidney disease and the current evidence on nutritional, pharmacological, and surgical strategies for the management of individuals with obesity and chronic kidney disease.

RECENT FINDINGS

Obesity can hurt the kidney via direct pathways, through the production of pro-inflammatory adipocytokines, and indirectly due to systemic complications of obesity, including type 2 diabetes mellitus and hypertension. In particular, obesity can damage the kidney through alterations in renal hemodynamics resulting in glomerular hyperfiltration, proteinuria and, finally, impairment in glomerular filtratation rate. Several strategies are available for weight loss and maintenance, such as the modification of lifestyle (diet and physical activity), anti-obesity drugs, and surgery therapy, but there are no clinical practice guidelines to manage subjects with obesity and chronic kidney disease. Obesity is an independent risk factor for the progression of chronic kidney disease. In subjects with obesity, weight loss can slow down the progression of renal failure with a significant reduction in proteinuria and improvement in glomerular filtratation rate. Specifically, in the management of subjects with obesity and chronic renal disease, it has been shown that bariatric surgery can prevent the decline in renal function, while further clinical studies are needed to evaluate the efficacy and safety on the kidney of weight reducing agents and the very low-calorie ketogenic diet.

Obesity and Kidney Transplant Candidates: An Outcome Analysis Based on Body Mass Index

Background Obesity is a well-established risk factor for a decline in renal function and post-operative complications. Also, obese patients suffer worse outcomes such as higher rates of wound complications, longer hospital stays, and delayed graft function (DGF) when compared to nonobese patients. The correlation between having a high BMI and the postoperative outcomes of kidney transplantation has not been investigated yet in Saudi Arabia. There is scarce evidence that patients with obesity who have undergone kidney transplantation are devoid of any complications before, during, or after their procedure. Methodology A retrospective cross-sectional study was conducted using charts of nearly 142 patients in King Abdullah Specialist Children's Hospital in Riyadh, who had kidney transplant surgery in the organ transplantation department. All Obese patients with BMI >29.9 who underwent Kidney Transplant Surgery in King Abdulaziz Medical City from 2015 to 2022 were used. Details of hospital admissions were retrieved. Results A total of 142 patients fulfilling the inclusion criteria were included. There was a significant difference between patients regarding pre-surgical history where all cases (100%; 2) with class three obesity were hypertensive and on dialysis versus (77.8%; 21) and (70.4%; 19) of class two obesity and (86.7%; 98) and (78.8%; 89) of class one obesity cases, respectively (P = 0.041). Regarding medical history, hypertension was reported among 121 (85%), followed by dialysis (77%; 110), diabetes mellitus (DM) (52%; 74), dyslipidemia (24%; 35), endocrine diseases (15%; 22), and cardiovascular diseases (16%; 23). Considering post-transplant complications, 14.1% (20) of the study cases had DM (16.8% of obese class one, 3.7% of obese class two, and none of obese class three; P = 0.996) and urinary tract infection (UTI) among 7% (10) of the cases (6.2% of obese class one, 11.1% of obese class two, and none of obese class three; P = 0.996). All these differences according to patients' BMI were statistically insignificant. Conclusion Obese patients are more likely to experience difficult intraoperative management along with a complicated postoperative course due to numerous concomitant comorbidities. Post-transplant DM (PTDM) was the most prominent post-transplant complication followed by UTI. A remarkable reduction in serum creatinine and blood urea nitrogen (BUN) has been observed at the time of discharge and after six months compared to pre-transplant measurements.

Who is trying to lose weight? Trends and prevalence in past-year weight loss attempts among US adults 1999-2018 at the intersection of race/ethnicity, gender, and weight status

Common stereotypes of those who desire or attempt to lose weight often center on the experience of White, thin women. However, prior studies have neglected how systems of oppression at intersection of race/ethnicity, gender, and weight status may interact to place certain subpopulations at elevated risk. Repeated cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 1999-2018 (n = 53,528), a population-representative sample of US adults, were used to 1) assess trends in past-year weight loss attempts using the Kendall-Mann trend test stratifying by race/ethnicity, gender, and weight status, and 2) estimate the adjusted prevalence of weight loss attempts over the combined 20-year period for combinations of race/ethnicity, gender, and weight status using logistic regression. There were significant monotonic trends from 1999 to 2018 for non-Hispanic Black men (43.8% to 67.8%, FDR adjusted p = .022) with an obese BMI, but not for any other groups. After adjusting for covariates, weight loss attempt prevalence was positively associated with BMI category for all race/ethnicity-gender combinations, although the degree of association differed. These findings underscore the need to use an intersectional lens in weight-related research. Despite limited long-term beneficial health impact, certain population subgroups, particularly Black men with an obese BMI, are increasingly trying to lose weight.

Bariatric Surgery Outcomes in Patients with Kidney Transplantation

Obesity and kidney transplantation (KTx) are closely related. Obesity increases the risk of chronic kidney disease and can be a relative contraindication for KTx. Besides, KTx recipients are predisposed to obesity and its comorbidities. Consequently, bariatric surgery (BS) emerges as a powerful therapeutic tool either before or after KTx. Since evidence regarding the best approach is still scarce, we aimed to describe renal and metabolic outcomes in a single centre with more than 15-year experience in both surgeries. Methods: A retrospective study including patients who had received a KTx either before or after BS. Usual metabolic and renal outcomes, but also new variables (as renal graft dysfunction) were collected for a minimum follow-up of 1-year post-BS. Results: A total of 11 patients were included: n = 6 (BS-post-KTx) and n = 5 (BS-pre-KTx). One patient was assessed in both groups. No differences in the main outcomes were identified, but BS-post-KTx group tended to gain more weight during the follow-up. The incidence of renal graft dysfunction was comparable (4/6 for BS-post-KTx, 3/5 for BS-pre-KTx) between groups. Conclusions: BS in patients with KTx appears to be safe and effective attending to metabolic and renal outcomes. These results seem irrespective of the time course, except for weight regain, which appears to be a common pattern in the BS-post-KTx group.

Recognition of Obesity and Perceptions of Weight Loss Management in Patients With Chronic Kidney Disease: A Retrospective Cross-Sectional Study

Background:

Obesity is, directly and indirectly, linked to the progression of chronic kidney disease (CKD). However, nephrologists’ recognition of obesity and willingness to address and manage obesity are unknown.

Objectives:

The aim of this article is to investigate if obesity is recognized and documented in the clinical encounter and to examine nephrologists’ perceptions of obesity and comfort with weight loss management.

Design:

We conducted a 2-part study. Part I used a retrospective chart review and part II used an anonymous online survey of practicing nephrologists (n = 14) in our center.

Setting:

The study took place in the Multi-care Kidney Clinic (MCKC) at London Health Sciences Centre in London, Ontario, Canada.

Patients:

In part I, we conducted a retrospective chart review of 10 random patients with advanced CKD and obesity (body mass index [BMI] > 30 kg/m²) from each of the nephrologists between January and December 2019.

Methods:

In part I, charts were assessed for documentation of obesity and/or a treatment plan (lifestyle counseling, pharmacologic intervention, and specialist referral). In part II, a survey completed by the nephrologists explored their current experience and perceptions of obesity and comfort with weight loss management. Responses were ranked on a 5-point Likert scale.

Results:

In all, 140 patient charts were reviewed. The median age was 69 (interquartile range [IQR] = 60-77) years, estimated glomerular filtration rate (eGFR) was 17 (IQR = 12-20) ml/min/1.73 m², weight was 99 (IQR = 90-116) kg, and BMI was 36 (IQR = 33-40) kg/m². Obesity with a BMI was documented in 36 (26%) charts, and only 2 (1%) documented a weight loss plan, which only included non-pharmacologic strategies. There were 13 survey responses (93% response rate). All nephrologists agreed that obesity negatively affects the health of patients with CKD. Twelve (92%) reported discussing obesity with patients, but none felt that they had time to treat it. All reported discussions of obesity would evoke a negative patient response, while 5 (38%) thought patients actually want to discuss obesity. Regarding treatment, 8 (62%) nephrologists felt comfortable with non-pharmacologic treatment, but only 1 respondent was comfortable with pharmacologic treatments. Twelve (92%) nephrologists thought patients should be referred to a specialist.

Limitations:

There was limited generalizability as this was a single center study. The BMI may reflect hypervolemia rather than body mass.

Conclusion:

In our study, nephrologists rarely document and manage obesity in patients with advanced CKD, despite their perception of treatment benefits. Improved outcomes of obesity management for patients with CKD will require increased knowledge and clinical tools to efficiently address obesity with patients.

Obesity and Post-Transplant Diabetes Mellitus in Kidney Transplantation

Worldwide, the prevalence obesity, diabetes, and chronic kidney disease is increasing apace. The relationship between obesity and chronic kidney disease is multidimensional, especially when diabetes is also considered. The optimal treatment of patients with chronic kidney disease includes the need to consider weight loss as part of the treatment. The exact relationship between obesity and kidney function before and after transplantation is not as clear as previously imagined. Historically, patients with obesity had worse outcomes following kidney transplantation and weight loss before surgery was encouraged. However, recent studies have found less of a correlation between obesity and transplant outcomes. Transplantation itself is also a risk factor for developing diabetes, a condition known as post-transplant diabetes mellitus, and is related to the use of immunosuppressive medications and weight gain following transplantation. Newer classes of anti-diabetic medications, namely SGLT-2 inhibitors and GLP-1 agonists, are increasingly being recognized, not only for their ability to control diabetes, but also for their cardio and renoprotective effects. This article reviews the current state of knowledge on the management of obesity and post-transplant diabetes mellitus for kidney transplant patients.

Conservative Management of Obesity in Kidney Transplant Candidates

OBJECTIVE

Obesity is prevalent in patients with chronic kidney disease and is associated with increased complications after kidney transplantation (KT). A body mass index limit is used in most transplant programs, though few studies have focused on conservative weight loss in KT candidates. The objective of this retrospective study is to evaluate the efficacy of a basic conservative weight management program in morbidly obese KT candidates and to perform a comprehensive nutritional evaluation.

METHODS

This retrospective study included patients with a body mass index (BMI) >35 kg/m^2, with grade IV or V chronic kidney disease. The conservative weight loss program consisted of anthropometric measurements every 3 months, consultation with a nutritionist, daily exercise, and counseling for healthier eating habits. Overall and quarterly BMI targets were defined. A subset of patients further underwent a comprehensive nutritional evaluation to measure socioeconomic characteristics, food intake behavior, motivation for change, and a 4-day food diary.

RESULTS

Eighty patients were observed for a mean of 24 months. Successful weight loss (BMI < 35 kg/m²) was achieved in 26.3%, associated with women and those already close to the limit. The mean 1-year excess body weight loss was 8.4%. No patient with a BMI >40 kg/m² was successful. The comprehensive nutritional evaluation was performed with 44 patients and found that only 14.6% had previously received nutritional counseling for weight loss. Cognitive restraint scored highest in the food-intake behavior. Most patients were motivated to lose weight with 66% in the action phase. There was little evidence of overeating with a recommended mean calculated daily caloric intake of 82.9%.

CONCLUSION

The conservative weight loss program can have limited but non-negligible, success. Future successful nutritional interventions should take into consideration this surprising comprehensive profile of morbidly obese KT candidates.

Failure to Advance Access to Kidney Transplantation over Two Decades in the United States

BACKGROUND

Extensive research and policies have been developed to improve access to kidney transplantation among patients with ESKD. Despite this, wide variation in transplant referral rates exists between dialysis facilities.

METHODS

To evaluate the longitudinal pattern of access to kidney transplantation over the past two decades, we conducted a retrospective cohort study of adult patients with ESKD initiating ESKD or placed on a transplant waiting list from 1997 to 2016 in the United States Renal Data System. We used cumulative incidence models accounting for competing risks and multivariable Cox models to evaluate time to waiting list placement or transplantation (WLT) from ESKD onset.

RESULTS

Among the study population of 1,309,998 adult patients, cumulative 4-year WLT was 29.7%, which was unchanged over five eras. Preemptive WLT (prior to dialysis) increased by era (5.2% in 1997-2000 to 9.8% in 2013-2016), as did 4-year WLT incidence among patients aged 60-70 (13.4% in 1997-2000 to 19.8% in 2013-2016). Four-year WLT incidence diminished among patients aged 18-39 (55.8%-48.8%). Incidence of WLT was substantially lower among patients in lower-income communities, with no improvement over time. Likelihood of WLT after dialysis significantly declined over time (adjusted hazard ratio, 0.80; 95% confidence interval, 0.79 to 0.82) in 2013-2016 relative to 1997-2000.

CONCLUSIONS

Despite wide recognition, policy reforms, and extensive research, rates of WLT following ESKD onset did not seem to improve in more than two decades and were consistently reduced among vulnerable populations. Improving access to transplantation may require more substantial interventions.

Management of Obesity in Adults with CKD

Obesity is a leading public health problem that currently affects over 650 million individuals worldwide. Although interest in the adverse effects of obesity has grown exponentially in recent years, less attention has been given to studying its management in individuals with CKD. This relatively unexplored area should be considered a high priority because of the rapid growth and high prevalence of obesity in the CKD population, its broad impact on health and outcomes, and its modifiable nature. This article begins to lay the groundwork in this field by providing a comprehensive overview that critically evaluates the available evidence related to obesity and kidney disease, identifies important gaps in our knowledge base, and integrates recent insights in the pathophysiology of obesity to help provide a way forward in establishing guidelines as a basis for managing obesity in CKD. Finally, the article includes a kidney-centric algorithm for management of obesity that can be used in clinical practice.

Weighing the waitlist: Weight changes and access to kidney transplantation among obese candidates

High body mass index is a known barrier to access to kidney transplantation in patients with end-stage kidney disease. The extent to which weight and weight changes affect access to transplantation among obese candidates differentially by race/ethnicity has received little attention. We included 10 221 obese patients waitlisted for kidney transplantation prior to end-stage kidney disease onset between 1995–2015. We used multinomial logistic regression models to examine the association between race/ethnicity and annualized change in body mass index (defined as stable [-2 to 2 kg/m²/year], loss [>2 kg/m²/year] or gain [>2 kg/m²/year]). We then used Fine-Gray models to examine the association between weight changes and access to living or deceased donor transplantation by race/ethnicity, accounting for the competing risk of death. Overall, 29% of the cohort lost weight and 7% gained weight; 46% received a transplant. Non-Hispanic blacks had a 24% (95% CI 1.12–1.38) higher odds of weight loss and 22% lower odds of weight gain (95% CI 0.64–0.95) compared with non-Hispanic whites. Hispanics did not differ from whites in their odds of weight loss or weight gain. Overall, weight gain was associated with lower access to transplantation (HR 0.88 [95% CI 0.79–0.99]) compared with maintenance of stable weight, but weight loss was not associated with better access to transplantation (HR 0.96 [95% CI 0.90–1.02]), although this relation differed by baseline body mass index and for recipients of living versus deceased donor organs. For example, weight loss was associated with improved access to living donor transplantation (HR 1.24 [95% CI 1.07–1.44]) in whites but not in blacks or Hispanics. In a cohort of obese patients waitlisted before dialysis, blacks were more likely to lose weight and less likely to gain weight compared with whites. Weight loss was only associated with improved access to living donor transplantation among whites. Further studies are needed to understand the reasons for the observed associations.

Is Body Mass Index a Significant Independent Risk Factor for Graft Failure and Patient Death in the Modern Immunosuppressive Era?

OBJECTIVES

Previous studies have shown that kidney transplant recipients with a high body mass index (BMI) have inferior graft and patient outcomes compared to patients with a lower BMI. We hypothesized that there would be secular improvements in outcomes among high BMI recipients. We used data from the United Network for Organ Sharing (UNOS) to determine whether obesity affects patient and graft outcomes following kidney transplantation in the modern immunosuppressive era.

METHODS

The study sample consisted of 69,749 recipients from 1987 to 1999 and 197,986 recipients from 2000 to 2016. BMI values were categorized into 11 tiers: below 18 kg/m², from 18 to 36 kg/m² at 2 kg/m²-unit increments, and above 36 kg/m². We created multivariate models to evaluate the independent effect of BMI on graft and patient outcomes, adjusting for factors known to affect graft success and patient survival.

RESULTS

Overall graft and patient survival has improved for all BMI categories. Cox regression modeling hazard ratios showed that the relative risk for graft loss, patient death, and patient death with a functioning graft in the modern immunosuppressive era (2000 to 2016) has significantly decreased compared to the earlier era (1987 to 1999), especially for living kidney transplant recipients.

CONCLUSIONS

The relative risk of graft failure and patient death with increasing BMI has appreciably decreased in the modern immunosuppressive era, especially for living donor transplant recipients. Withholding transplantation from patients with higher BMIs may no longer be justifiable on grounds of worse clinical outcomes.

Modest rates and wide variation in timely access to repeat kidney transplantation in the United States

Success of transplantation is not limited to initial receipt of a donor organ. Many kidney transplant recipients experience graft loss following initial transplantation and the benefits of expedited placement on the waiting list and retransplantation extend to this population. Factors associated with access to repeat transplantation may be unique given experience with the transplant process and prior viability as a candidate. We examined the incidence, risk factors, secular changes, and center-level variation of preemptive relisting or transplantation (PRLT) for kidney transplant recipients in the United States with graft failure (not due to death) using Scientific Registry of Transplant Recipients data from 2007 to 2018 (n = 39 557). Overall incidence of PRLT was 15% and rates of relisting declined over time. Significantly lower PRLT was evident among patients who were African American and Hispanic, males, older, obese, publicly insured, had lower educational attainment, were diabetic, had longer dialysis time prior to initial transplant, shorter graft survival, longer distance to transplant center, and resided in distressed communities. There was significant variation in PRLT by center, median = 13%, 10th percentile = 6%, 90th percentile = 24%. Cumulatively, results indicate that despite prior access to transplantation, incidence of PRLT is modest with pronounced clinical, social, and center-level sources of variation suggesting opportunities to improve preemptive care among patients with failing grafts.

[Nutrition in chronic kidney disease]

INTRODUCTION

Chronic kidney disease patients often also present protein-calorie malnutrition, and it is a powerful predictor of morbidity and mortality. In this article, causes and management are shown, highlighting oral and parenteral nutritional supplementation, especially during dialysis process.