Pre-Transplant Weight Loss and Survival after Kidney Transplantation

Body mass index in pediatric kidney transplant selection criteria

BACKGROUND

Obesity is associated with increased complications, rejection, and graft loss after kidney transplantation in adult and pediatric recipients. Elevated body mass index (BMI) is a common contraindication to transplant at adult kidney transplant programs; however, there is no data on such limitations for pediatric patients.

METHODS

Between October and December 2022, we conducted a survey of Pediatric Nephrology Research Consortium centers assessing the use of BMI in pediatric kidney transplant evaluation. Centers reporting utilization of BMI cutoffs were invited to submit patient-level data on children declined for active transplant listing due to BMI.

RESULTS

Thirty-nine centers responded to the survey (42% response rate); 51% include BMI in their written listing criteria, with a median BMI "cutoff" of 39 kg/m2 (range 30-50 kg/m2). Between January 1, 2016, and December 31, 2021, 30 children at 15 transplant centers were declined for listing status due to BMI. Patient-level data was provided for 19 children (63%) who were denied active listing status; median BMI was 42 kg/m2 (range 35.8-49.4 kg/m2) and 84% were on dialysis. One year after evaluation, seven patients (37%) had proceeded to active wait list status. Eight (42%) remained in inactive status and four (21%) were unlisted; ten of these 12 patients (83%) were on dialysis.

CONCLUSIONS

The use of BMI in pediatric kidney transplant evaluation and listing varies among centers, but BMI limits access to transplant for some children. More information is needed on the outcomes of obese pediatric kidney candidates who are and are not transplanted, to guide development of national and international consensus.

Robotic kidney transplantation

Kidney transplantation is the best treatment option for patients with end-stage renal disease owing to improved survival and quality of life compared with dialysis. The surgical approach to kidney transplantation has been somewhat stagnant in the past 50 years, with the open approach being the only available option. In this scenario, evidence of reduced surgery-related morbidity after the introduction of robotics into several surgical fields has induced surgeons to consider robot-assisted kidney transplantation (RAKT) as an alternative approach to these fragile and immunocompromised patients. Since 2014, when the RAKT technique was standardized thanks to the pioneering collaboration between the Vattikuti Urology Institute and the Medanta hospital (Vattikuti Urology Institute-Medanta), several centres worldwide implemented RAKT programmes, providing interesting results regarding the safety and feasibility of this procedure. However, RAKT is still considered an alternative procedure to be offered mainly in the living donor setting, owing to various possible drawbacks such as prolonged rewarming time, demanding learning curve, and difficulties in carrying out this procedure in challenging scenarios (such as patients with obesity, severe atherosclerosis of the iliac vessels, deceased donor setting, or paediatric recipients). Nevertheless, the refinement of robotic platforms through the implementation of novel technologies as well as the encouraging results from multicentre collaborations under the umbrella of the European Association of Urology Robotic Urology Section are currently expanding the boundaries of RAKT, making this surgical procedure a real alternative to the open approach.

The application of body mass index-based eligibility criteria may represent an unjustified barrier to renal transplantation in people with obesity

The prevalence of both obesity and end-stage kidney disease is increasing. In many centres, obesity is considered a relative contraindication to kidney transplantation due to an association with short- and longer-term adverse outcomes. This leads to delayed transplant waitlisting and longer organ waiting times for people with obesity. This review evaluates whether intentional pre-transplant weight loss in people with obesity improves kidney transplant outcomes. There are currently no data showing that non-surgical weight loss of 10% or more improves graft or patient survival over 4-5 years. Outcomes from bariatric surgery cohorts have been generally neutral or favourable after pre-transplant weight loss of ~25%. Given the survival benefit of kidney transplantation compared to maintenance dialysis, and the difficulty of achieving and maintaining weight loss, the common practice of recommending weight loss to achieve arbitrary targets prior to waiting list activation needs to be carefully considered.

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.

Effect of Pretransplant Body Mass Index on Kidney Transplant Recipient and Graft Long-term Survival

BACKGROUND

The aim of the study was to assess the influence of pretransplant body mass index (BMI [calculated as weight in kilograms divided by height in meters squared]) to the graft and patient 5- and 10-year survival.

METHODS

Our study group consisted of 706 patients who received their kidney transplant after the year 2000.

RESULTS

Almost half, 51.9% (n = 372) of the patients had BMI < 25, and 47.6% (n = 336) had BMI ≥ 25. Patients who were overweight or obese were significantly older than other groups (P = .01). The 5-year recipient survival was significantly better in the BMI < 25 group (n = 291, 79.5%) than the BMI ≥ 25 group (n = 238, 70.2%, P < .05). In addition, 10-year recipient survival was better in the BMI < 25 group (n = 175, 47.8%) compared with the BMI ≥ 25 group (n = 127, 37.5%, P < .05). Similarly, 5-year graft survival was better in the BMI < 25 group (66.9%, n = 242) compared with the BMI ≥ 25 group (61.1%, n = 204, P < .05). However, 10-year graft survival was not statistically significant (P = .08). Regarding the impact of diabetes on survival, we found patients with diabetes mellitus to have worse survival in all groups (P = .009).

CONCLUSIONS

Recipient graft survival was affected by diabetes mellitus independently from being overweight. In the current study, we demonstrated that pretransplant obesity or being overweight affects recipient and graft short-term survival, but long-term comparison of patients who were overweight or obese with patients with normal BMI revealed minimal recipient survival differences and in graft survival analysis no difference. Although in many studies obesity and being overweight predict a bad outcome for kidney transplant recipient survival, our research did not fully confirm it. Diabetes mellitus had worse outcome in all patients groups.

Management of obesity in kidney transplant candidates and recipients: A clinical practice guideline by the Descartes working group of ERA

The clinical practice guideline Management of Obesity in Kidney Transplant Candidates and Recipients was developed to guide decision-making in caring for people with end-stage kidney disease (ESKD) living with obesity. The document considers the challenges in defining obesity, weighs interventions for treating obesity in kidney transplant candidates as well as recipients and reflects on the impact of obesity on the likelihood of wait-listing as well as its effect on transplant outcomes. It was designed to inform management decisions related to this topic and provide the backdrop for shared decision-making. This guideline was developed by the European Renal Association’s Developing Education Science and Care for Renal Transplantation in European States working group. The group was supplemented with selected methodologists to supervise the project and provide methodological expertise in guideline development throughout the process. The guideline targets any healthcare professional treating or caring for people with ESKD being considered for kidney transplantation or having received a donor kidney. This includes nephrologists, transplant physicians, transplant surgeons, general practitioners, dialysis and transplant nurses. Development of this guideline followed an explicit process of evidence review. Treatment approaches and guideline recommendations are based on systematic reviews of relevant studies and appraisal of the quality of the evidence and the strength of recommendations followed the Grading of Recommendations Assessment, Development and Evaluation approach. Limitations of the evidence are discussed and areas of future research are presented.

Abdominal Panniculectomy Can Simplify Kidney Transplantation in Obese Patients

BACKGROUND

Obesity is frequently present in patients suffering from end-stage renal disease (ESRD). However, overweight kidney transplant candidates are a challenge for the transplant surgeon. Obese patients tend to develop a large abdominal panniculus after weight loss creating an area predisposed to wound-healing disorders. Due to concerns about graft survival and postoperative complications after kidney transplantation, obese patients are often refused in this selective patient cohort. The study aimed to analyze the effect of panniculectomies on postoperative complications and transplant candidacy in an interdisciplinary setting.

METHODS

A retrospective database review of 10 cases of abdominal panniculectomies performed in patients with ESRD prior to kidney transplantation was conducted.

RESULTS

The median body mass index was 35.2 kg/m2 (range 28.5-53.0 kg/m2) at first transplant-assessment versus 31.0 kg/m2 (range 28.0-34.4 kg/m2) at panniculectomy, and 31.6 kg/m2 (range 30.3-32.4 kg/m2) at kidney transplantation. We observed no major postoperative complications following panniculectomy and minor wound-healing complications in 2 patients. All aside from 1 patient became active transplant candidates 6 weeks after panniculectomy. No posttransplant wound complications occurred in the transplanted patients.

CONCLUSION

Abdominal panniculectomy is feasible in patients suffering ESRD with no major postoperative complications, thus converting previously ineligible patients into kidney transplant candidates. An interdisciplinary approach is advisable in this selective patient cohort.

Obesity in Renal Transplantation

BACKGROUND

Data from the WHO show an increasing rate of overweight and obesity in general population in the last decades. This increase in obesity also affects population with end-stage renal disease (ESRD) and kidney transplant (KT) candidates.

SUMMARY

In this review, we focused on how obesity impacts on KT stages: access to KT and outcomes of KT candidates; how to reduce weight and its consequences; short and long-term outcomes in obese recipients and the impact of weight variations; and the implications of obesity in living donor KT. We searched MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials until November 30, 2020. We selected systematic reviews and meta-analyses and randomized clinical trials. When no such reports were found for a topic, observational studies were included in the assessment. Key Messages: Although obesity is a risk factor to present worst outcomes after KT, several studies have demonstrated a survival benefit compared to patients who continue on dialysis. There is a need for a public health campaign to raise awareness in KT candidates and to highlight the importance of self-care, increasing exercise, healthy diet, and weight loss.

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.

Early Postoperative Complications and Outcomes of Kidney Transplantation in Moderately Obese Patients

BACKGROUND

Obese renal transplant recipients (body mass index [BMI] ≥30 kg/m²) are at risk of delayed graft function and postoperative complications, such as infections or delayed wound healing. There is also a tendency to exclude extremely obese patients from transplantation (KTx). Nonetheless, no association between obesity and increased mortality has been reported. The aim of this study is to evaluate the effect of BMI on the most common surgical and infectious complications after KTx.

MATERIALS AND METHODS

An observational study in 872 patients transplanted from 2010-2017 was conducted. Median BMI was 24.6 (13.9-34.3), and 8.3% of the group was obese. Patient records were searched for early postoperative complications: lymphocele or hematoma (>33 mL), urinary leakage, or urinary tract infection (UTI). Mann-Whitney U and χ² or Fisher exact tests were used. P < .05 was considered statistically significant. The study complies with the Helsinki Congress and the Istanbul Declaration.

RESULTS

Renal primary nonfunction was observed in 1.4% (12/872) of patients. Surgical or infectious complications occurred in 52.7% (453/860) of patients. No correlation between BMI and complication rate was noted. Complications were observed in 56.9% (41/72) of obese vs 52.3% (412/788) of nonobese patients (P = .448), including lymphocele in 15.3% vs 16.4% (P = .810), hematoma in 22.2% vs 19.2% (P = .530), urinary leakage in 1.4% vs 4.6% (P = .203), and UTI in 31.9% vs 32.9% (P = .873), respectively.

CONCLUSIONS

Recipient's BMI has no significant association with the most common surgical complications after KTx. There is no need to delay KTx in moderately obese patients.

Obesity and listing for renal transplantation: weighing the evidence for a growing problem

A 56-year-old female patient was referred to the transplant assessment clinic in July 2016. She started haemodialysis in 2012 for renal failure due to urinary tract infections. She is doing very well on dialysis and has an excellent exercise tolerance without shortness of breath or angina. She has had no infections since starting dialysis and no other comorbidity, except well-controlled hypertension and hyperparathyroidism requiring treatment with cinacalcet. Clinical examination is essentially normal except for truncal obesity with height 167 cm and weight 121 kg, giving her a body mass index of 43.4. Can she be listed for a renal transplant? If not, which target weight should be given to the patient before she can be transplant listed? Which interventions, if any, should be recommended to achieve weight loss?