Blog entry by Arif Khwaja
So last week I saw 2 patients within a few hours each of whom tells their own story. The first was in transplant clinic. She was transplanted 10 years ago and has perfect kidney function. Her BMI was 40 at the time of transplant and is now 50. She sailed through the transplant without any technical or imunnological problems. Transplantation was undoubtedly a life-saver – she had factor V Leiden mutation and was running out of access due to recurrent clotting of access.
In the afternoon I saw a 50 year old patient on haemodialysis. She had a BMI of 35 and had previously been active on the transplant list. She was otherwise well with no other significant comorbidity. She was reviewed by a surgeon who felt that as she had significant central obesity, transplantation would be technically challenging and so she was suspended from the list until her BMI was 30. She asked to see me as she was in a terrible state. She was literally starving herself and had lost 8Kg but needed to lose a further 8 kg before her BMI hit the magic 30. She pleaded for me to be reactivated on the transplant list though I explained this was ultimately a surgical decision. What was clear was that i) I had never seen her look so ill as she did now she was trying to lose weight and ii) for her to maintain herself at a BMI of 30 she would need to continue to starve herself.
So these two cases prompted me to look a bit at the literature around obesity and transplantation and the following themes emerged:
- While it has long been recognised that higher BMI associates with survival on dialysis there is also some data to suggest that weight loss is harmful. Molnar and colleagues looked at over 14000 wait listed dialysis patients and found that those who had loss greater than 5Kg had a death hazard ratio of 1.51. Of course this doesn’t mean necessarily that intentional weight loss is harmful but it is food for thought when telling dialysis patients to lose weight.
- Whilst surgical complications post transplantation ( e.g. wound infections) do increase with BMI, the data on the effect of obesity on graft survival is conflicting. Streja and colleagues analysed10,090 kidney transplant recipients were followed for up to 6 years posttransplantation. Low pretransplant BMI (<22 kg/m2) showed a trend toward higher posttransplant mortality, whereas obesity (BMI ≥ 30 kg/m2) was not associated with mortality, albeit it showed a trend toward higher graft loss. A smaller analysis of over 1000 patients showed recipient BMI to correlate with delayed graft function which of course in itself is a risk factor for poorer graft survival. In a 20 year follow up of around 1800 patients from Holland, BMI increment post transplantation and BMI at one year were both much more powerful predictors of adverse graft and patient survival than pre-transplant BMI. Indeed pretransplant BMI didn’t have a statistically significant association with adverse outcomes
- The key question perhaps isn’t whether the obese are more likely to run into complications but whether they still have a survival advantage from transplantation. In an analysis of around 7000 patients who had a BMI of >30 who were wait listed for transplantation, the incidence of mortality in those who underwent transplantation was still less than half of those who stayed on dialysis waiting for a kidney. The beneficial effect of transplantation was lost when BMI>41
So what to do? Well given the fact that the safety of weight loss isn’t established in dialysis patients (and may be harmful in some patients) we need to be honest with patients and tell them that we don’t know whether this is safe - it may well be safe to lose weight but it may not be and so we need to tell patients that. There is no evidence to show that weight loss pre-transplant improves outcomes post-transplant and the observational data seems to suggest that patients with a pre-transplant BMI of upto 40 still gain a survival benefit from transplantation. Therefore as ever we need to make individual decisions on a holistic evaluation of the patient taking into account all other comorbidities rather than plucking arbitrary numbers and targets out of the air. This is of course only opinion but I'm not convinced that the patient with a BMI of 35 who is currently starving herself to get to a BMI of 30, will get any health benefit from such starvation.
Associations of body mass index and weight loss with mortality in transplant-waitlisted maintenance hemodialysis patients. Molnar MZ, Streja E, Kovesdy CP, Bunnapradist S, Sampaio MS, Jing J, Krishnan M, Nissenson AR, Danovitch GM, Kalantar-Zadeh K. Am J Transplant. 2011 Apr;11(4):725-36
Associations of pretransplant weight and muscle mass with mortality in renal transplant recipients. Streja E, Molnar MZ, Kovesdy CP, Bunnapradist S, Jing J, Nissenson AR, Mucsi I, Danovitch GM, Kalantar-Zadeh K. Clin J Am Soc Nephrol. 2011 Jun;6(6):1463-73.
Recipient and donor body mass index as important risk factors for delayed kidney graft function. Transplantation. 2012 Mar 15;93(5):524-9.Weissenbacher A, Jara M, Ulmer H, Biebl M, Bösmüller C, Schneeberger S, Mayer G, Pratschke J, Öllinger R.
Effect of obesity on the outcome of kidney transplantation: a 20-year follow-up.Hoogeveen EK, Aalten J, Rothman KJ, Roodnat JI, Mallat MJ, Borm G, Weimar W, Hoitsma AJ, de Fijter JW. Transplantation. 2011 Apr 27;91(8):869-74.