Impact of recipient obesity on living donor kidney transplant outcomes: a single-center experience

Effect of Recipient Body Mass Index on Kidney Transplantation Outcomes: A Systematic Review and Meta-analysis by the Transplant Committee from the French Association of Urology

CONTEXT

The impact of recipient obesity on kidney transplantation (KT) outcomes remains unclear.

OBJECTIVE

The aim of this study was to perform a systematic review and meta-analysis to appraise all available evidence on the outcomes of KT in obese patients (body mass index [BMI] ≥30 kg/m2) versus nonobese patients (BMI <30 kg/m2).

EVIDENCE ACQUISITION

A systematic review and meta-analysis was performed. Search was conducted in the MEDLINE OvidSP, Web of Science, Google Scholar, Embase, and Cochrane databases to identify all studies reporting the outcomes of KT in obese versus nonobese recipients.

EVIDENCE SYNTHESIS

Fifty-two articles met the inclusion criteria. Delayed graft function and surgical complications were significantly higher in obese recipients (delayed graft function: relative risk [RR]: 1.44, 95% confidence interval [CI]: 1.32-1.57, p < 0.01; surgical complications: RR: 1.74, 95% CI: 1.36-2.22, p < 0.0001). Five-year patient survival (RR: 0.96, 95% CI: 0.92-1.00, p = 0.01), 10-yr patient survival (RR: 0.90, 95% CI: 0.84-0.97, p = 0.006), and 10-yr graft survival (RR: 0.87, 95% CI: 0.79-0.96, p = 0.01) were significantly inferior in the obese group.

CONCLUSIONS

KT in obese recipients was associated with lower patient and graft survival, and higher delayed graft function, acute rejection, and medical and surgical complications than nonobese recipients. In the current situation of organ shortage and increasing prevalence of obesity, ways to optimize KT in this setting should be investigated.

PATIENT SUMMARY

Compared with nonobese population, kidney transplantation in obese recipients has inferior patient and graft survival, and higher medical and surgical complications.

Body Mass Index Thresholds and the Use of Bariatric Surgery in the Field of Kidney Transplantation in Germany

Background

Obesity in the recipient is linked to inferior transplant outcome. Consequently, access to kidney transplantation (KT) is often restricted by body mass index (BMI) thresholds. Bariatric surgery (BS) has been established as a superior treatment for obesity compared to conservative measures, but it is unclear whether it is beneficial for patients on the waiting list.

Methods

A national survey consisting of 16 questions was sent to all heads of German KT centers. Current situation of KT candidates with obesity and the status of BS were queried.

Results

Center response rate was 100%. Obesity in KT candidates was considered an important issue (96.1%; n = 49/51) and 68.6% (n = 35/51) of departments responded to use absolute BMI thresholds for KT waiting list access with ≥ 35 kg/m² (45.1%; n = 23/51) as the most common threshold. BS was considered an appropriate weight loss therapy (92.2%; n = 47/51), in particular before KT (88.2%; n = 45/51). Sleeve gastrectomy was the most favored procedure (77.1%; n = 37/51). Twenty-one (41.2%) departments responded to evaluate KT candidates with obesity by default but only 11 (21.6%) had experience with ≥ n = 5 transplants after BS. Concerns against BS were malabsorption of immunosuppressive therapy (39.2%; n = 20/51), perioperative morbidity (17.6%; n = 9/51), and malnutrition (13.7%; n = 7/51).

Conclusions

Obesity is potentially limiting access for KT. Despite commonly used BMI limits, only few German centers consider BS for obesity treatment in KT candidates by default. A national multicenter study is desired by nearly all heads of German transplant centers to prospectively assess the potentials, risks, and safety of BS in KT waitlisted patients.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11695-022-06000-4.

The Impact of Recipient Demographics on Outcomes from Living Donor Kidneys: Systematic Review and Meta-Analysis

Background and Aims: Recipient demographics affect outcomes after kidney transplantation. The aim of this study was to assess, for kidneys retrieved from living donors, the effect of recipient sex, ethnicity, and body mass index (BMI) on delayed graft function (DGF) and one-year graft function, incidence of acute rejection (AR), and recipient and graft survivals. Methods: A systematic review and meta-analysis was performed. EMBASE and MEDLINE databases were searched using algorithms through Ovid. Web of Science collection, BIOSIS, CABI, Korean Journal database, Russian Science Citation Index, and SciELO were searched through Web of Science. Cochrane database was also searched. Risk of bias was assessed using the NHBLI tools. Data analysis was performed using Revman 5.4. Mean difference (MD) and risk ratio (RR) were used in analysis. Results: A total of 5129 studies were identified; 24 studies met the inclusion criteria and were analysed. Female recipients were found to have a significantly lower serum creatinine 1-year-post renal transplantation (MD: −0.24 mg/dL 95%CI: −0.18 to −0.29 p < 0.01) compared to male recipients. No significant difference in survival between male and female recipients nor between Caucasians and Africans was observed (p = 0.08). However, Caucasian recipients had a higher 1-year graft survival compared to African recipients (95% CI 0.52−0.98) with also a lower incidence of DGF (RR = 0.63 p < 0.01) and AR (RR = 0.55 p < 0.01). Recipient obesity (BMI > 30) was found to have no effect on 1-year recipient (p = 0.28) and graft survival (p = 0.93) compared to non-obese recipients although non-obese recipients had a lower rate of DGF (RR = 0.65 p < 0.01) and AR (RR = 0.81 p < 0.01) compared to obese recipients. Conclusions: Gender mismatch between male recipients and female donors has negative impact on graft survival. African ethnicity and obesity do not to influence recipient and graft survival but negatively affect DGF and AR rates.

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.

Efficacy and Safety of Intra-gastric Balloon Placement in Dialyzed Patients Awaiting Kidney Transplantation

BACKGROUND

The number of obese patients who are candidates for renal transplantation has considerably increased, but obesity can be a barrier to kidney transplantation. Weight loss is often difficult through diet alone. We studied the efficacy and tolerance of the intra-gastric balloon (IGB) procedure in obese patients who were undergoing dialysis and were candidates for a renal transplantation.

PATIENTS AND METHODS

Obese patients (BMI > 30 kg/m²) who were candidates for renal transplantation were prospectively included in the study between 2010 and 2012. The balloon was inserted and removed during a gastric endoscopy under general anesthesia. The treatment lasted 6 months. The end point was a decrease in BMI after 6 months. Body impedance spectrometry (BIS) and nutritional statute were evaluated initially and then after IGB removal.

RESULTS

Seventeen patients (nine females and eight males) with a mean age of 53.4 years [19.4-69.4] were included. The decrease in body mass index (BMI) during the 6-month placement was 3 kg/m² (from 37.7 to 34.4 kg/m²). The mean weight loss was 7 kg. The mean percentage of excess weight loss after 6 months was 20.2 (± 11.4). The tolerance was good without any complications. Eleven patients underwent kidney transplantation.

CONCLUSION

IGB in obese dialyzed patients who are candidates for renal transplantation is safe and effective. However, the amount of weight loss can vary.

Effect of Obesity on Clinical Outcomes of Kidney Transplant Patients

PURPOSE

Correlating with the obesity epidemic, the number of obese transplant candidates is increasing. This study was designed to evaluate the effect of obesity on the survival of our kidney transplant recipients.

METHODS

Among 1033 kidney transplants performed during the last 7.5 years in our center, 750 adult recipients were transplanted from living donors and were evaluated, and 561 of them were included in the study. Demographic and clinical data were collected. Body mass index (BMI) values at the time of transplant and post-transplant during the first year, the presence of delayed graft function, hospitalization duration, number of readmissions within the first year post-transplant, presence of post-transplant diabetes mellitus (PTDM) and cardiovascular disease, and graft and patient survival rates at 1, 3, and 5 years were investigated.

RESULTS

Obesity (BMI >30) was observed in 148 (19.7%) at the time of the transplant (initial obesity) and in 174 (23.2%) recipients at post-transplant first year. Initial obesity was not only found to be correlated with delayed wound healing (P = .03), increased hospitalization duration (P = .03), number of readmissions within the first year (P = .04), presence of PTDM (P = .02), and cardiovascular disease (P = .03) but also with lower graft survival rate (P = .04) at the first year. On the other hand, obesity at post-transplant the first year was associated with lower 3- and 5-year grafts (P = .04 and P = .03, respectively) and 5-year patient (P = .03) survival rates.

CONCLUSION

Obesity should not be considered as a contraindication for kidney transplantation; however, to achieve better results, certain precautions should be taken pre- and postoperatively.

Single Center Experience With Robotic Kidney Transplantation for Recipients With BMI of 40 kg/m2 Or Greater: A Comparison With the UNOS Registry

BACKGROUND

Obesity represents a barrier to kidney transplantation, but the increasing prevalence among renal failure patients has forced some centers to carefully consider such candidates. Morbidly obese patients may be at increased risk of delayed graft function, higher postoperative complications, and inferior graft outcomes. Nevertheless, mortality on the waiting list remains significantly higher than after transplant. We have applied minimally invasive surgery to perform kidney transplant in individuals with body mass index (BMI) of 40 kg/m or greater. We compared our results to the national United Network of Organ Sharing database.

METHODS

The United Network of Organ Sharing registry was reviewed for adult living donor kidney transplant recipients with BMI of 40 kg/m or greater performed from September 2009 to December 2014. We compared transplants performed with robotic technique (RKT) versus patients performed with open surgery at all US centers including our own (open kidney transplant). Subgroup analysis in patients with BMI of 45 kg/m or greater was conducted. We compared outcomes including patient and graft survival, renal function, and technical complications.

RESULTS

Robotic kidney transplantation group had a significantly higher mean BMI overall. The 1-year patient and graft survival rates were similar between groups. Renal function was also similar at 6, 12, and 36 months. Thrombosis caused 1.3% of the graft losses in open kidney transplant and 0% in the RKT group. Interestingly, 52.8% of the overall experience in patients with BMI of 45 kg/m or greater was performed with the robotic technique.

CONCLUSIONS

Robotic surgery offers similar patient and graft survivals with comparable renal function to open technique. Robotic kidney transplantation permits transplantation in extreme BMI categories without additional technical complications. Further studies are required to establish the role of RKT for obese candidates but preliminary data are encouraging.

Influence of the recipient body mass index on the outcomes after kidney transplantation

PURPOSE

The relationship between the body mass index (BMI) of kidney transplant recipients and outcomes after kidney transplantation (KT) is not fully understood and remains controversial. We studied the influence of BMI on clinically relevant outcomes in kidney transplant recipients.

METHODS

In this retrospective single-centre study, all patients who underwent kidney transplantation at our institution between January 2007 and December 2012 were included. Demographic data and BMI were correlated with the clinical course of the disease, rejection rates, delayed graft function rates, and graft and patient survival.

RESULTS

During the study period, 384 single KTs (130 women and 254 men) were performed. Seventeen percent of the transplants were transplanted within the Eurotransplant Senior Programme (ESP). Most of the transplants were performed using organs that were obtained from donors after brain death (DBD), and living donor kidney transplants were performed in 22.4% of all transplants. The median BMI of the recipients was 25.9 kg/m². Additionally, 13.5% of the recipients had a BMI of 30-34.9 kg/m² and 3.9% had a BMI >35 kg/m². A BMI >30 kg/m² was significantly associated with primary non-function of the kidney (p = 0.047), delayed graft function (p = 0.008), and a higher rate of loss of graft function (p = 0.015). The glomerular filtration rate 12 months after KT was significantly lower in recipients with a BMI >30 kg/m². Multivariate analysis revealed that recipient BMI, among other factors, was an independent risk factor for delayed graft function and graft survival. Patients with a BMI >30 kg/m² had an almost four times higher risk for surgical site infection than did recipients with a lower BMI.

CONCLUSIONS

Increased BMI at kidney transplantation is a predictor of adverse outcomes, including delayed graft function. These findings demonstrate the importance of the careful selection of patients and pre-transplant weight reduction, although the role of weight reduction for improving graft function is not clear.

Kidney transplantation in obese patients

The World Health Organization estimated that in 2014, over 600 million people met criteria for obesity. In 2011, over 30% of individuals undergoing kidney transplant had a body mass index (BMI) 35 kg/m² or greater. A number of recent studies have confirmed the relationship between overweight/obesity and important comorbidities in kidney transplant patients. As with non-transplant surgeries, the rate of wound and soft tissue complications are increased following transplant as is the incidence of delayed graft function. These two issues appear to contribute to longer length of stay compared to normal BMI. New onset diabetes after transplant and cardiac outcomes also appear to be increased in the obese population. The impact of obesity on patient survival after kidney transplantation remains controversial, but appears to mirror the impact of extremes of BMI in non-transplant populations. Early experience with (open and laparoscopic) Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy support excellent weight loss (in the range of 50%-60% excess weight lost at 1 year), but experts have recommended the need for further studies. Long term nutrient deficiencies remain a concern but in general, these procedures do not appear to adversely impact absorption of immunosuppressive medications. In this study, we review the literature to arrive at a better understanding of the risks related to renal transplantation among individuals with obesity.

Body mass index and outcome in renal transplant recipients: a systematic review and meta-analysis

BACKGROUND

Whether overweight or obese end stage renal disease (ESRD) patients are suitable for renal transplantation (RT) is often debated. The objective of this review and meta-analysis was to systematically investigate the outcome of low versus high BMI recipients after RT.

METHODS

Comprehensive searches were conducted in MEDLINE OvidSP, Web of Science, Google Scholar, Embase, and CENTRAL (the Cochrane Library 2014, issue 8). We reviewed four major guidelines that are available regarding (potential) RT recipients. The methodology was in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and written based on the PRISMA statement. The quality assessment of studies was performed by using the GRADE tool. A meta-analysis was performed using Review Manager 5.3. Random-effects models were used.

RESULTS

After identifying 5,526 studies addressing this topic, 56 studies were included. We extracted data for 37 outcome measures (including data of more than 209,000 RT recipients), of which 26 could be meta-analysed. The following outcome measures demonstrated significant differences in favour of low BMI (<30) recipients: mortality (RR = 1.52), delayed graft function (RR = 1.52), acute rejection (RR = 1.17), 1-, 2-, and 3-year graft survival (RR = 0.97, 0.95, and 0.97), 1-, 2-, and 3-year patient survival (RR = 0.99, 0.99, and 0.99), wound infection and dehiscence (RR = 3.13 and 4.85), NODAT (RR = 2.24), length of hospital stay (2.31 days), operation duration (0.77 hours), hypertension (RR = 1.35), and incisional hernia (RR = 2.72). However, patient survival expressed in hazard ratios was in significant favour of high BMI recipients. Differences in other outcome parameters were not significant.

CONCLUSIONS

Several of the pooled outcome measurements show significant benefits for 'low' BMI (<30) recipients. Therefore, we postulate that ESRD patients with a BMI >30 preferably should lose weight prior to RT. If this cannot be achieved with common measures, in morbidly obese RT candidates, bariatric surgery could be considered.

Morbid obesity is not an independent predictor of graft failure or patient mortality after kidney transplantation

OBJECTIVE

Obesity is often an absolute contraindication to kidney transplant, but an internal analysis of our center's recipients suggests that not all obese populations exhibit poor outcomes. We used national data to compare outcomes in select groups of morbidly obese and normal-weight recipients after kidney transplant.

DESIGN

This study was a retrospective analysis of the Organ Procurement and Transplant Network/United Network for Organ Sharing database.

SUBJECTS

The study sample consisted of 30,132 morbidly obese (body mass index [BMI] 35-40 kg/m(2)) and normal-weight (BMI 18.5-24.9 kg/m(2)) patients who underwent primary kidney-only transplantation between 2001 and 2006.

MAIN OUTCOME MEASURE

Crude 3-year graft and patient survival rates of morbidly obese and normal-weight subgroups were evaluated. Logistic regression modeling compared 3-year graft failure and patient mortality in morbidly obese and normal-weight subgroups with opposite characteristics. Kaplan-Meier survival curves were created for 3-year graft and patient survival. Cox proportional hazard regression modeling was used to determine hazards for patient and graft mortality.

RESULTS

No differences in crude graft and patient survival rates were seen between normal weight and morbidly obese recipients who were African American, diabetic, and 50 to 80 years of age. Morbidly obese recipients who were nondialysis dependent, nondiabetic, had good functional status, and received living-donor transplants had significantly lower 3-year graft failure and patient mortality risk compared with normal-weight recipients who were dialysis dependent, diabetic, had poor functional status, and received a deceased-donor transplant, respectively (P < .01). Morbidly obese recipients have significantly lower graft and patient survival curves compared with normal-weight recipients; however, multivariate regression analysis reveals that morbid obesity is not an independent predictor of graft failure or patient mortality.

CONCLUSIONS

Morbid obesity is not independently associated with graft failure or patient mortality; therefore, it should not be used as a contraindication to kidney transplantation.

Kidney transplantation in the obese transplant candidates: to transplant or not to transplant?

The prevalence of obesity (body mass index ≥30 kg/m(2)) at the time of transplantation among kidney transplant recipients in the United States has doubled between 1987 and 2001 and continues to increase inexorably. Single-center and large registry studies in kidney transplant recipients demonstrated that high body mass index (BMI) at transplant is associated with increased risk of wound and surgical site infections, delayed graft function (DGF), acute rejection episodes, and graft loss, among others. Hence, in many centers, obese transplant candidates are denied a transplant based on their body mass index (BMI) alone. The impact of obesity on short- and long-term graft and patient outcomes after kidney transplantation are herein revisited, followed by the authors' proposed approach to evaluate and select obese transplant candidates for a kidney transplant. Suggested interventions to optimize the health of such candidates are also discussed.