Welcome to Transplant Month

The first transplant activity is the next NephJC which is on Tuesday September 8. We are switching things up and both the GMT and American chat will be on Tuesday. The GMT at 8 PM and the American is  at the usual time of 9 PM Eastern.

The other activities of Transplant Month:

The first Chat of Transplant Month:

Introduction

Kidney transplantation in obese patients is a controversial topic. Most of the data in the literature is retrospective and without conclusive results. Complicating the assessment is the “dialysis paradox” or reverse epidemiology where obese patients have a survival advantage in hemodialysis. We generally believe that every ESRD patient deserves to be evaluated for a kidney transplantation but if these patients do significantly worse with transplants and better with dialysis the approach to these patients must have some nuance. Does the "dialysis paradox" continue after kidney transplantation.

For additional color, take a look at this Renal Fellow Network post on pre-transplant weight loss.   

Article Summary

Recipient obesity and outcomes after kidney transplantation: a systemic review and meta-analysis

 Hill CJ, Courtney AE, Cardwell CR, Maxwell AP, Lucarelli G, Veroux M, Furriel F, Cannon RM, Hoogeveen EK, Doshi M, McCaughan JA.

PMID: 26044837

Methods

The authors searched Medline, Embase and Cochrane Library up through March 31, 2013; they found 6,962 references. They then filtered the studies based on their inclusion criteria and culled 6,892 articles, leaving them with 70. After further review, they limited their meta-analysis to 17 studies.

Inclusion Criteria:

  • Observational studies

  • Obesity as defined by the WHO definition of BMI: >30 kg/m2.

  • Outcomes: DGF, death-censored, survival and recipient survival.

  • Studies that assessed outcomes in adult patients.

Exclusion Criteria:

  • Use of alternative anthropometric measures to define obesity.

  • BMI analysed as a continuous variable

  • Studies focused on multi-organ transplants

  • Studies in abstract format.

They were very careful in minimizing duplicated data and contacted authors to gather additional unreported data where necessary. There analysis looked at 138,081 patients. To assess study quality, they used the Newcastle-Ottawa scale (More info).

By the numbers:

  • 9 single-center studies

  • 8 studies assessed survival

  • 12 studies assessed frequency of DGF

Results

After adjustment of the analyzed data:

  • There was no difference in mortality risk in obese recipients (HR = 1.24, 95% CI 0.90–1.70). This was from 5 studies with 83,416 patients.

  • Obesity was associated with an higher risk of death-censored graft loss (HR 1.06, 95% CI 1.01–1.12). This was from 5 studies with 83,416 patients.

  • Obesity was associated with an increased likelihood of DGF (OR= 1.68, 95% CI= 1.39–2.03). This was from 4 studies with 28,847 patients.

“We were unable to detect a significant difference in mortality risk between obese transplant recipients and those with a normal BMI after adjustment for common co-morbidities and transplant-related factors.”

Discussion

Although this meta-analysis included a large number of studies from different countries and patients with different ethnicities and backgrounds, it had some limitations:

  • They limited the analysis to observational studies

  • Few of the studies had adjusted results available

  • There is no comment on induction or maintenance immunosuppressive therapy

  • They only used one method to assess obesity

  • There were no sub-categories of BMI (30-34 kg/m2, 35-39.9 kg/m2, etc…) and no comment of obese recipients with BMI >40 kg/m2

And probably most importantly the top line result was though there was a higher likelihood of DGF and allograft loss, survival after kidney transplantation was no different between obese recipients and those with normal BMI.

It has also been reported that obese recipients have higher wound infection rates and longer hospitalizations in comparison to people with normal BMI. Though this study did not address this issue, there has been improvements due to newer operative techniques. For instance, the University of Illinois at Chicago initiated a robotic-assisted kidney transplantation with good results on patients with BMI >40 kg/m2. Future research and RCTs are needed to determine whether obesity has a true impact on peri-operative complications and allograft survival long term.

Summary by Hector Madariaga