*Purpose: Morbid obesity is a barrier to kidney transplantation (KT) due to increased perioperative risks and worse outcomes. Bariatric surgery (BS) is increasingly performed in patients with obesity and end stage renal disease prior to transplantation to optimize transplant candidacy. However, it is yet unclear how BS may affect post-transplant outcomes. A systematic review was conducted to look at outcomes after KT in recipients who had received BS to improve KT candidacy.  

*Methods: MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials were searched from database inception to 11/28/2021 for studies describing outcomes of kidney transplant recipients that underwent BS prior to KT. Outcomes after BS, % excess weight loss, time to KT, as well as transplant outcomes including surgical complications, graft failure, delayed graft function, and new onset diabetes after transplantation (NODAT) were extracted. 

*Results: Ten studies were included, all single center, 90% retrospective, reporting a total of 227 patients (108 females, 47.5%). Type of BS included laparoscopic sleeve gastrectomy, Roux-en-Y gastric bypass, and laparoscopic gastric bending. Patients BMI median prior to transplant, post-BS, ranged from 28.8 to 33.6kg/m². Across studies, patients % excess weight loss following BS ranged from 50.2 to 80.2%, and time from BS to transplantation ranged from 9 to 72 months. The rate of postoperative complications, vascular, urinary, and wound infection, ranged from 5 to 28.4%.   No one-year mortality was documented. Rates of one-year graft loss ranged from 0 to 29%, delayed graft function 5 to 71%, and NODAT 0 to 45.5%.

*Conclusions: Bariatric surgery has been shown to be associated with lower rates of delayed graft function and NODAT in several studies. The utilization of BS prior to KT may be a way to improve post KT outcomes in addition to addressing barriers to transplantation in patients with end stage renal disease and morbid obesity. Given the paucity and variability of the data, future larger-scale studies are warranted to better understand the impact of BS on KT outcomes in obese patients. 

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