The Problem

Kidney transplant remains the gold standard treatment for End Stage Renal Disease (ESRD) patients. This is also true for obese patients, whereby kidney transplant, albeit lower, but still confers a significant survival advantage over dialysis (1,2). As of January 2017 there are over 98,000 patients on the United Network for Organ Sharing (UNOS) kidney transplant waiting list, approximately 37% of these are obese i.e. Body Mass Index (BMI) >30kg/m2 (3) . More than a third of this obese cohort is either severely (BMI >35kg/m2) or morbidly obese (BMI >40kg/m2). This is in keeping with the Centers for Disease Control and prevention (CDC) reported statistics of adult obesity rates of 36.5% in the United States (4). Obesity, a rising global epidemic, is considered to be an independent risk factor for cardiovascular disease. This is in addition to the association of obesity with diabetes, and dyslipidemia further potentiating the cardiovascular risk. Specific to kidney transplantation, cardiovascular events are a leading (42%) cause of mortality after a kidney transplant (5).

The US kidney transplant registry data shows that kidney transplants in patients with BMI greater than 35 kg/m2 have a higher risk of graft failure and patient mortality alongside increased risk of Delayed Graft Function (DGF) and infections (6,7). This translates to longer hospital stay (7) adding further to the economic burden in care of obese kidney transplant patients. The Dialysis and Transplant Registry data of Australia and New Zealand also concludes that obesity is associated with poorer graft and patient survival in kidney transplant patients (8).

Therefore, although kidney transplantation, a better treatment option than dialysis for the obese ESRD patients, but when compared to the non-obese ERSD patients, they are riskier and poorer in outcomes. Therefore, the Scientific Registry of Transplant Recipients (SRTR) whilst collecting and analyzing outcome data of transplant centers in the United States, utilizes risk adjustment models to compensate for recipient risks for the transplant centers. This reporting system minimizes the ‘cream skimming’ (9) behavior whereby providers could select the most profitable recipients i.e. the ones with minimal risk. But despite this risk adjustment model incorporating recipient BMI as an adjusted risk factor, obesity amongst ESRD patients still leads to a higher rate of denial of potential recipients during the pre-transplant evaluation phase (10).

Furthermore, after being listed for a kidney transplant, the likelihood of being bypassed for an organ offer by a provider is 4 to 13% higher for recipients with BMI 35-40 kg/m2 and 22 to 23% higher for BMI >40 kg/m2 (11). It therefore is no surprise that the median time to transplantation from listing, is significantly higher for patients with BMI >35 kg/m2 (11).

Robotic Assisted Kidney Transplant

Robotic Assisted Kidney Transplantation (RAKT) was first performed in France in 2001(12), but failed to garner enthusiasm as an alternative to open conventional approach in kidney transplant. The advantage of ‘minimally invasive approach’, that surgical robot offered in kidney transplant was limited in acceptance due to complex technique, steep learning curve and high costs associated with the Robot. Therefore, transplant centers developed and applied individual criterion for the use of Robot in kidney transplants.

Lately, RAKT is developing its niche in obese patients by certain practitioners. A comparative analysis of 28 patients with a mean BMI of 42.6±7.8 kg/m2 in the study group of RAKT vs 38.1±5.4kg/m2 BMI in the control arm of open conventional surgery for kidney transplant from living donors at a single center showed, Surgical Site Infections (SSIs) were significantly lower (0% vs 28.6%) in the robotic arm (13). Multivariate analysis by another group looking at SSIs in renal transplantation as a whole concluded that, BMI >30 kg/m2 independently predicted incidence of SSI, and it turn SSI was a significant risk factor for graft loss and approached near significance for patient mortality (14). Therefore, the promising results of RAKT in obese patients by Benedetti et al (13) albeit small in number were supportive of RAKT in obese ESRD patients, however they experienced higher incidence of Delayed Graft Function (DGF) and higher hospital costs associated with the Robotic device. It has been well known that DGF after survival (15,16), and given the steep learning curve of RAKT, the anastomosis time is significantly longer. This in turn leads to DGF due to longer warm ischemic time. Therefore, RAKT on one hand is supportive of graft and patient survival by minimizing SSIs, on the other hand though, it negatively impacts, graft and patient survival due to the higher incidence of DGF. Therefore the acceptance of RAKT in obese patients, who inherently suffer worse graft and patient survival as compared to non-obese patients, is debatable. The comparative study by Benedetti et al in comparing RAKT vs open surgery for obese patients also failed to show any impact on reducing the length of hospital stay with RAKT, despite the ‘minimally invasive’ advantage of the Robotic technique (13). However, one group did show reduced length of hospital stay and lower analgesic use with RAKT, but they utilized RAKT in nonobese patients, which is a whole different paradigm (17).

Conclusion

RAKT, a relatively modern technique of kidney transplantation has been slow to gain momentum, despite being more than a decade old. Its application in obese recipients certainly minimizes SSIs, but adds to the incidence of DGF. Therefore, larger studies are needed to ascertain the impact of lower SSI vs higher DGF on patient and graft survival. We also need to ascertain the minimally invasive advantage of RAKT in reducing length of hospital stay and complications. This will better assess the balance of benefit vs risk with RAKT and which patients should advantage from it Therefore in our opinion RAKT has certain, but limited application in kidney transplantation and therefore should require careful selection of patients as a prerequisite whilst considering RAKT.

Conflict of Interest: None

1. Stewart DE, Garcia VC, Rosendale JD, Klassen DK, Carrico BJ (2016) Diagnosing the Decades-Long Rise in the Deceased Donor Kidney Discard Rate in the U.S.Transplantation 2016.
2. https://optn.transplant.hrsa.gov
3. Meier-Kriesche HU, Arndorfer JA, Kaplan B (2002) The impact of body mass index on renal transplant outcomes: a significant independent risk factor for graft failure and patient death. Transplantation 73: 70-74.
4. Gore JL, Pham PT, Danovitch GM, Wilkinson AH, Rosenthal JT, et al. (2006) Obesity and outcome following renal transplantation. Am J Transplant 6: 357-363.
5. Chang SH, Coates PT, McDonald SP (2007) Effects of body mass index at transplant on outcomes of kidney transplantation. Transplantation 84: 981-987.
6. Barros PP (2003) Cream-skimming, incentives for efficiency and payment system. J Health Econ 22: 419-43.
7. Holley JL, Monaghan J, Byer B, Bronsther O (1998) An examination of the renal transplant evaluation process focusing on cost and the reasons for patient exclusion. American Journal of Kidney Diseases 32: 567-574.
8. Segev DL, Simpkins CE, Thompson RE, Locke JE, Warren DS, et al. (2008) Obesity impacts access to kidney transplantation. J Am SocNephrol 19: 349-355.
9. Pelletier SJ, Maraschio MA, Schaubel DE, Dykstra DM, Punch JD, et al. (2003) Survival benefit of kidney and liver transplantation for obese patients on the waiting list. ClinTranspl 2003: 77-88.
10. Glanton CW, Kao TC, Cruess D, Agodoa LY, Abbott KC (2003) Impact of renal transplantation on survival in end-stage renal disease patients with elevated body mass index. Kidney Int 63: 647-653.
11. Hoznek A, Zaki SK, Samadi DB, Salomon L, Lobontiu A, et al. (2002) Robotic assisted kidney transplantation: an initial experience. J Urol 167: 1604-1606.
12. Oberholzer J, Giulianotti P, Danielson KK, Spaggiari M, Bejarano-Pineda L, et al.(2013) Minimally invasive robotic kidney transplantation for obese patients previously denied access to transplantation. Am J Transplant 13: 721-728.
13. Sood A, Ghosh P, Menon M, Jeong W, Bhandari M, et al (2015) Robotic renal transplantation: Current status. Journal of Minimal Access Surgery 11: 35-39.
14. Butala NM, Reese PP, Doshi MD, Parikh CR (2013) Is Delayed Graft Function Causally Associated with Long-Term Outcomes after Kidney Transplantation? Instrumental Variable Analysis. Transplantation 95: 1008-1014.
15. Grosso G, Corona D, Mistretta A, Zerbo D, Sinagra N, et al (2012) Delayed graft function and long-term outcome in kidney transplantation. Transplant Proc 44: 1879-1883.