The incidence rate of end-stage renal disease (ESRD) is projected to increase 11%-18% by 2030, with the exact rate dependent on obesity trends. Nearly 40% of the adult US population is obese, with class 3 obesity prevalence (body-mass index [BMI] ≥40)—a common upper limit for wait-listing at kidney transplant centers—of 5.5% for men and 9.9% for women. Obesity and ESRD are intricately linked, as the former contributes to the latter, mediated at least partly by obesity-related comorbidities (hypertension and diabetes) and hyperfiltration injury. As the 2 epidemics converge, proactive solutions are needed to halt further kidney injury, mitigate the effects of metabolic comorbidities, and help obese patients achieve access to kidney transplantation.
In this issue of the American Journal of Transplantation (AJT), Kassam et al report their single-center experience of laparoscopic sleeve gastrectomy (LSG) in morbidly obese chronic kidney disease (CKD) and ESRD patients who were simultaneously being evaluated for kidney transplant, the largest series of its kind. Of 499 such patients, 243 underwent LSG and 71.7% achieved a BMI ≤ 40, the center's threshold for listing. The authors report an impressively low 30-day readmission rate (1.2%) and no 90-day mortalities. Similar to the general bariatric surgery population, patients experienced significant improvements in metabolic comorbidities. The prevalence of hypertension and diabetes decreased from 85.8% to 52.1% and 59.6% to 32.5%, respectively. For those without complete resolution, there was a significant decrease in the number of antihypertensive agents required and a more than 50% decrease in daily insulin requirements. Of the 198 ESRD patients, 35.8% lost sufficient weight to be listed for transplant and 22.7% were transplanted on average 1.9 years post-LSG. Of the 14 patients who pursued medical weight loss alone at the transplant center, 3 (21.4%) lost sufficient weight to achieve listing and subsequent transplant. Within the 13 CKD 3A/3B LSG patients, there was an overall improvement in their mean estimated glomerular filtration rate (43.5 vs 58.5 mL/min); however, this difference in renal function was not seen when the Cockroft-Gault formula was applied, nor was it seen in the CKD stage 1, 2, or 4 patients.
These exciting data portend growth in the hybrid field of "transplant bariatrics" to address the burgeoning epidemics of obesity and end-stage organ disease; however, a number of important questions arise from this work. Of the patients who chose to follow at the transplant center for their medical weight loss therapy, 21.4% were able to lose weight and achieve transplant, similar to the 22.7% seen in the LSG group. It is unclear whether the successes of the 3 patients in the medical weight loss group are replicable on a larger scale or if the similar transplant rates in the 2 groups are an aberration related to small sample size. Many large-scale studies of bariatric surgery vs medical weight loss treatment in the non-CKD/ESRD population demonstrate that significant and sustained weight loss is associated with the former and not the latter. The possibility exists, however, that the additional enticement of achieving transplant is a powerful motivator for obese CKD/ESRD patients that distinguishes them from the general obese population. The authors are to be commended on their outstanding surgical outcomes, though it is unclear whether these outcomes are generalizable. Existing data suggest that they are not. In a recent study of the national Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program data, Cohen and colleagues found that ESRD patients undergoing bariatric surgery had an 11.59-, 3.10-, and 2.97-fold higher odds of 30-day mortality, reoperation, and readmission compared to propensity score–matched controls without kidney disease. Indeed, higher complications could translate into lower wait-listing and transplant rates than the 35.8% and 22.7% reported in the current study. Additionally, there is the concern that bariatric surgery and its concomitant weight loss can lead to significant protein malnutrition and frailty, which are well-documented to lead to worse wait-list and posttransplant outcomes. Indeed, weight loss of ≥10% prior to deceased donor kidney transplant was associated with an 11% higher hazard of graft loss and 18% higher hazard of death, though it is unclear whether these associations hold true in the case of intentional weight loss. Finally, and perhaps most tantalizing, is the possibility that dramatic weight loss can halt progression of CKD, as the authors noted in a subanalysis of CKD stage 3A/3B patients and as has been suggested in other studies. While it has never been proven, transplant bariatrics could delay or even obviate the need for transplant altogether. Further study is needed to prove whether such an effect exists and if it does, which patients might benefit and when the optimal timing of bariatric surgery is.
National Center for Advancing Translational Sciences, Grant/Award Number: 1KL2TR003097; National Institute of Diabetes and Digestive and Kidney Diseases, Grant/Award Number: 5R01DK113980.
American Journal of Transplantation. 2020;20(2):329-330. © 2020 Blackwell Publishing