When There is No Guidance From the Guidelines: Renal Transplantation in Recipients With Class III Obesity

Whilst renal transplantation is the optimal treatment for many patients with end-stage kidney disease, the latest international guidelines are unable to make recommendations for the management of patients with end-stage kidney stage kidney disease and Class III Obesity (BMI ≥40 kg/m2). Data on all adult patients receiving a kidney-only-transplant in the UK between 2015-2021 were analysed from a prospectively collected database and interrogated across a range of parameters. We then analysed in detail the outcomes of patients transplanted at the highest-volume unit. There were 22,845 renal transplants in the study time-period; just 44 (0.2%) were performed in recipients with a BMI ≥40 kg/m2. Most transplant centres did not transplant any patients in this category. In the centre with the highest volume, there were 21 transplants (9 living donor) performed in 20 individuals (13 male, median age 46 years). One-year patient and death-censored graft survival was 95% and 85%. Successful transplantation is possible in patients with BMI ≥40 kg/m2 but carries additional risk. Obesity should not be the sole factor considered when deciding on transplant suitability. Restricting transplantation to a small number of high-volume centres in each country should be considered to optimize outcomes.

Nonlinear relationship between body mass index and clinical outcomes after kidney transplantation: A dose-response meta-analysis of 50 observational studies

BACKGROUND

Exact dose-response relationship between body mass index at transplantation and clinical outcomes after kidney transplantation remained unclear, and no specific body mass index threshold and pretransplant weight loss aim were recommended for kidney transplantation candidates among transplant centers.

METHODS

PubMed, Embase, Web of Science, and Cochrane Library were searched for literature published up to December 31, 2019. The two-stage, random effect meta-analysis was performed to estimate the dose-response relationship between body mass index and clinical outcomes after kidney transplantation.

RESULTS

Ninety-four studies were included for qualitative assessment and 50 for dose-response meta-analyses. There was a U-shaped relationship between graft loss, patient death, and body mass index. Body mass index with the lowest risk of graft loss was 25.2 kg/m², and preferred body mass index range was 22-28 kg/m². Referring to a body mass index of 22 kg/m², the risk of graft loss was 1.088, 0.981, 1.003, and 1.685 for a body mass index of 18, 24, 28, and 40 kg/m², respectively. Body mass index with the lowest risk of patient death was 24.7 kg/m², and preferred body mass index range was 22-27 kg/m². Referring to a body mass index of 22 kg/m², the patient death risk was 1.115, 0.981, 1.032, and 2.634 for a body mass index of 18, 24, 28, and 40 kg/m², respectively. J-shaped relationships were observed between body mass index and acute rejection, delayed graft function, primary graft nonfunction, and de novo diabetes. Pair-wise comparisons showed that higher body mass index was also a risk factor for cardiovascular diseases, hypertension, infection, longer length of hospital stay, and lower estimated glomerular filtration rate level.

CONCLUSION

Underweight and severe obesity at transplantation are associated with a significantly increased risk of graft loss and patient death. A target body mass index at kidney transplantation is 22-27 kg/m².

Pre-Kidney Transplant Unintentional Weight Loss Leads to Worse Post-Kidney Transplant Outcomes

BACKGROUND

Weight loss before kidney transplant (KT) is a known risk factor for weight gain and mortality; however, whereas unintentional weight loss is a marker of vulnerability, intentional weight loss might improve health. We tested whether pre-KT unintentional and intentional weight loss have differing associations with post-KT weight gain, graft loss, and mortality.

METHODS

Among 919 KT recipients from a prospective cohort study, we used adjusted mixed effects models to estimate post-KT BMI trajectories, and Cox models to estimate death-uncensored graft loss, death-censored graft loss, and all-cause mortality by one-year pre-KT weight change category [stable weight (change≤5%), intentional weight loss (loss>5%), unintentional weight loss (loss>5%), and weight gain (gain>5%)].

RESULTS

Mean age was 53 years, 38% were Black, and 40% were female. In the pre-KT year, 62% of recipients had stable weight, 15% had weight gain, 14% had unintentional weight loss, and 10% had intentional weight loss. In the first three years post-KT, BMI increases were similar among those with pre-KT weight gain and intentional weight loss, and lower compared to those with unintentional weight loss (difference +0.79 kg/m2/year, 95% CI: 0.50-1.08 kg/m2/year, p < 0.001). Only unintentional weight loss was independently associated with higher death-uncensored graft loss (adjusted Hazard Ratio [aHR]=1.80, 95% CI:1.23-2.62), death-censored graft loss (aHR=1.91, 95% CI:1.12-3.26) and mortality (aHR=1.72, 95% CI:1.06-2.79) relative to stable pre-KT weight.

CONCLUSIONS

This study suggests that unintentional, but not intentional, pre-KT weight loss is an independent risk factor for adverse post-KT outcomes.

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.

Association Between Weight Loss Before Deceased Donor Kidney Transplantation and Posttransplantation Outcomes

RATIONALE & OBJECTIVE

There is debate on whether weight loss, a hallmark of frailty, signals higher risk for adverse outcomes among recipients of deceased donor kidney transplantation (DDKT).

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Using national Organ Procurement and Transplantation Network data, we included all DDKT recipients in the United States between December 4, 2004, and December 3, 2014, who were adults (aged ≥ 18 years) when listed for DDKT.

EXPOSURES

Relative pre-DDKT weight change as a continuous predictor and categorized as <5% weight change from listing to DDKT, ≥5% to <10% weight loss, ≥10% weight loss, ≥5% to <10% weight gain, and ≥10% weight gain.

OUTCOMES

We examined 3 post-DDKT outcomes: (1) transplant hospitalization length of stay (LOS) in days, (2) all-cause graft failure, and (3) mortality.

ANALYTIC APPROACH

Unadjusted fractional polynomial methods, multivariable log-gamma models, and multivariable Cox proportional hazards models.

RESULTS

Among 94,465 recipients of DDKT, median pre-DDKT weight change was 0 (interquartile range, -3.5 to +3.9) kg. There were nonlinear unadjusted associations between relative pre-DDKT weight loss and longer transplant hospitalization LOS, higher all-cause graft loss, and higher mortality. Compared with recipients with <5% pre-DDKT weight change (n = 49,366; 52%), recipients who lost ≥10% of their listing weight (n = 10,614; 11%) had 0.66 (95% CI, 0.23-1.09) days longer average transplant hospitalization LOS (P = 0.003), 1.11-fold higher graft loss (adjusted HR [aHR], 1.11; 95% CI, 1.06-1.17; P < 0.001), and 1.18-fold higher mortality (aHR, 1.18; 95% CI, 1.11-1.25; P < 0.001) independent of recipient, donor, and transplant factors. Pre-DDKT dialysis exposure, listing body mass index category, and waiting time modified the association of pre-DDKT weight change with hospital LOS (interaction P < 0.10), but not with all-cause graft loss and mortality.

LIMITATIONS

Unmeasured confounders and inability to identify volitional weight change. Also, the higher significance level set to increase the power of detecting interactions with the fixed sample size may have resulted in increased risk for type 1 error.

CONCLUSIONS

DDKT recipients with ≥10% pre-DDKT weight loss are at increased risk for adverse outcomes and may benefit from augmented support post-DDKT.

Obesity in Kidney Transplantation: Impact on Transplant Candidates, Recipients, and Donors

Obesity is now common among children and adults who are kidney transplant candidates and recipients. It is associated with an increased risk of cardiovascular disease and kidney failure. This also pertains to potential living kidney donors with obesity. Obese patients with end-stage renal disease benefit from transplantation as do nonobese patients, but obesity is also associated with more risk. A complicating factor is that obesity is also associated with increased survival on maintenance dialysis in adults, but not in children. The assessment of obesity and body habitus should be individualized. Body mass index is a common but imperfect indicator of obesity. The medical management of obesity in renal failure patients is often unsuccessful. Bariatric surgery, specifically laparoscopic sleeve gastrectomy, can result in significant weight loss with reduced morbidity, but many patients do not agree to undergo this treatment. The best approach to manage obese transplant candidates and recipients is yet unresolved.

Obesity and bariatric intervention in patients with chronic renal disease

Obesity is associated with chronic metabolic conditions that directly and indirectly cause kidney parenchymal damage. A review of the literature was conducted to explore existing evidence of the relationship between obesity and chronic kidney disease as well as the role of bariatric surgery in improving access to kidney transplantation for patients with a high body mass index. The review showed no definitive evidence to support the use of a transplant eligibility cut-off parameter based solely on the body mass index. Moreover, in the pre-transplant scenario, the obesity paradox is associated with better patient survival among obese than non-obese patients, although promising results of bariatric surgery are emerging. However, until more information regarding improvement in outcomes for obese kidney transplant candidates is available, clinicians should focus on screening of the overall frailty condition of transplant candidates to ensure their eligibility and addition to the wait list.

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

There is clear evidence that survival rates following transplantation far exceed those for remaining on dialysis, regardless of body size measured by body mass index (BMI). Studies over the past 15 years also suggest little to no difference in long-term outcomes, including graft survival and mortality, irrespective of BMI, in contrast to earlier evidence. However, weight bias still exists, as access to kidney transplantation remains inequitable in centers using arbitrary BMI limits. Clinicians faced with the decision regarding listing based on body size are not helped by conflicting recommendations in national and international guidelines. Therefore, in clinical practice, obesity, and recommendations for weight loss, remain a controversial issue when assessing suitability for kidney transplantation. Obesity management interventions in end-stage kidney disease (ESKD), whether for weight loss for transplantation listing or for slowing kidney disease progression, are under-explored in trial settings. Bariatric surgery is the most successful treatment for obesity, but carries increased risk in the ESKD population, and the desired outcome of kidney transplant listing is not guaranteed. Centers that limit transplants to those meeting arbitrary levels of body mass, rather than adopting an individualized assessment approach, may be unfairly depriving many ESKD patients of the survival and quality of life benefits derived from kidney transplantation. However, robotic kidney transplantation surgery holds promise for reducing perioperative risks related to obesity, and may therefore represent an opportunity to remove listing criteria based on size.

Weight management strategies for those with chronic kidney disease: A consensus report from the Asia Pacific Society of Nephrology and Australia and New Zealand Society of Nephrology 2016 renal dietitians meeting

AIM

The aim of the present study was to develop a consensus report to guide dietetic management of overweight or obese individuals with chronic kidney disease (CKD).

METHODS

Six statements relating to weight management in CKD guided a comprehensive review of the literature. A summary of the evidence was then presented at the renal nutrition meeting of the 2016 Asia Pacific Society of Nephrology and Australia and New Zealand Society of Nephrology. Majority agreement was defined as group agreement on a statement of between 50-74%, and consensus was considered ≥75% agreement. The recommendations were developed via a mini Delphi process.

RESULTS

Two statements achieved group consensus: the current guidelines used by dietitians to estimate energy requirements for overweight and obese people with CKD are not relevant and weight loss medications may be unsafe or ineffective in isolation for those with CKD. One statement achieved group agreement: Meal replacement formulas are safe and efficacious in those with CKD. No agreement was achieved on the statements of whether there is strong evidence of benefit for weight loss prior to kidney transplantation; whether traditional weight loss strategies can be used in those with CKD and if bariatric surgery in those with end stage kidney disease is feasible and effective.

CONCLUSION

There is a limited evidence base to guide the dietetic management of overweight and obese individuals with CKD. Medical or surgical strategies to facilitate weight loss are not recommended in isolation and require a multidisciplinary approach with the involvement of a skilled renal dietitian.

Weight Loss in Advanced Chronic Kidney Disease: Should We Consider Individualised, Qualitative, ad Libitum Diets? A Narrative Review and Case Study

In advanced chronic kidney disease, obesity may bring a survival advantage, but many transplant centres demand weight loss before wait-listing for kidney graft. The case here described regards a 71-year-old man, with obesity-related glomerulopathy; referral data were: weight 110 kg, Body Mass Index (BMI) 37 kg/m², serum creatinine (sCr) 5 mg/dL, estimated glomerular filtration rate (eGFR) 23 mL/min, blood urea nitrogen (BUN) 75 mg/dL, proteinuria 2.3 g/day. A moderately restricted, low-protein diet allowed reduction in BUN (45–55 mg/dL) and good metabolic and kidney function stability, with a weight increase of 6 kg. Therefore, he asked to be enrolled in a weight-loss program to be wait-listed (the two nearest transplant centres required a BMI below 30 or 35 kg/m²). Since previous low-calorie diets were not successful and he was against a surgical approach, we chose a qualitative, ad libitum coach-assisted diet, freely available in our unit. In the first phase, the diet is dissociated; he lost 16 kg in 2 months, without need for dialysis. In the second maintenance phase, in which foods are progressively combined, he lost 4 kg in 5 months, allowing wait-listing. Dialysis started one year later, and was followed by weight gain of about 5 kg. He resumed the maintenance diet, and his current body weight, 35 months after the start of the diet, is 94 kg, with a BMI of 31.7 kg/m², without clinical or biochemical signs of malnutrition. This case suggests that our patients can benefit from the same options available to non-CKD (chronic kidney disease) individuals, provided that strict multidisciplinary surveillance is assured.

Increased alloreactivity and adverse outcomes in obese kidney transplant recipients are limited to those with diabetes mellitus

Previous studies on patient and allograft outcomes of obese kidney transplant recipients (KTRs) remain controversial. To what extent obesity-related comorbidities contribute to adverse outcomes, however, hasn't been addressed. We studied all KTRs from 2005 to 2012. 29 (4%), 317 (48%), 217 (33%), 76 (12%), and 21 KTRs (4%) were identified as underweight, normal-weight, overweight, obese, and morbid obese, respectively. 33 of 97 obese KTRs (34%) had pre-existent diabetes. Samples were collected before transplantation and at +1, +2, +3months posttransplantation. Donor-reactive T-cells were measured using an interferon-γ Elispot assay. Obese KTRs showed an increased incidence pre-existent diabetes (p<0.001), but no differences for hypertension and coronary artery disease (p>0.05). Among obese KTRs, those with pre-existent diabetes showed inferior patient and allograft survival, worse allograft function, delayed graft function, and prolonged hospitalization (p<0.05). Interestingly, no differences were observed between obese non-diabetic, normal-weight diabetic, and normal-weight non-diabetic KTRs (p>0.05). Obese diabetic KTRs showed higher frequencies of donor-reactive T-cells pretransplantation (p<0.05). Our results suggest that the increased risk of mortality, allograft loss, delayed graft function, and prolonged hospitalization in obese KTRs is limited to those with diabetes. A state of obesity-related inflammation plus hyperglycemia may trigger increased alloreactivity and should call for adequate immunosuppression.

From chronic kidney disease to kidney transplantation: The impact of obesity and its treatment modalities

Obesity is associated with worse short-term outcomes after kidney transplantation but the effect on long-term outcomes is unknown. Although some studies have reported worse outcomes for obese recipients when compared to recipients with a BMI in the normal range, obese recipients who receive a transplant have better outcomes than those who remain wait-listed. Whether transplant candidates should be advised to lose weight before or after transplant has been debated and this is mainly due to the gap in the literature linking pre-transplant weight loss with better outcomes post-transplantation. The issue is further complicated by the use of BMI as a metric of body fat, the obesity paradox in dialysis patients and the different ethical viewpoints of utility versus equity. Measures used to reduce weight loss, including orlistat and bariatric surgery (in particular those with a malabsorptive component), have been associated with enteric hyperoxaluria with consequent risk of nephrolithiasis and oxalate nephropathy. In this review, we discuss the evidence regarding the use of weight loss measures in the kidney transplant candidate and recipient with a view to recommending whether weight loss should be pursued before or after kidney transplantation.

Moderator's view: Pretransplant weight loss in dialysis patients: cum grano salis

A high Body Mass Index (BMI) predicts delayed graft function, all cause and cardiovascular death after transplantation but such risk excess is apparently confined to patients included in studies performed before 2000. Perhaps with the exception of morbid obesity (BMI > 40), clinical outcomes in transplanted obese patients are definitely better than in listed dialysis patients who don't receive a renal transplant. Furthermore the new Scientific Registry of Transplant Recipients (SRTR) risk calculator incorporates BMI into the prediction model of the global risk for the graft's and patient's survival appropriately framing the risk of obesity in a multidimensional risk context. In the aggregate, available knowledge suggests that clinical decisions on weight loss before transplantation should be context specific. Renal transplant patients from living donors have substantial better survival in comparison to well matched dialysis patients listed for the same intervention at all BMI categories. Therefore renal transplantation in obese patients with a living donor may be prioritized. The attitude of fully informed obese patients at accepting the risk driven by transplantation, the experience of the surgical team with obese patients (including also robotic surgery) are of obvious importance. Renal transplantation should be timely considered when reasonable attempts at weight loss failed or appear overtly unrealistic. Transplantation in morbidly obese patients with BMI > 40, a category where the survival advantage of transplantation vs dialysis is probably small and still uncertain, particularly so in African-Americans, should be deferred until significant weight loss is achieved.