H-14: Transplant monitoring
H-09: clinic
Effects of Obesity on Kidney Transplantation Outcomes: A
Systematic Review and Meta-Analysis
Nicoletto, Bruna B.1; Fonseca, Natasha K. O.2; Manfro, Roberto C.3,4; Gonçalves, Luiz Felipe
S.3,4; Leitão, Cristiane Bauermann5,6; Souza, Gabriela C.7,8
Transplantation 27 July 2014 - Volume 98 - Issue 2 - p 167-176
ABSTRACT
Background
The effects of obesity on outcomes reported after kidney transplantation have been
controversial. The purpose of this systematic review and meta-analysis was to elucidate this
issue.
Methods
MEDLINE, EMBASE, Cochrane Library, and gray literature were searched up to August 6,
2013. Studies that compared obese and nonobese patients who underwent kidney
transplantation and evaluated one of these outcomes—delayed graft function (DGF), acute
rejection, graft or patient survival at 1 or 5 years after transplantation, or death by
cardiovascular disease (CVD)—were included. Two independent reviewers extracted the
data and assessed the quality of the studies.
Results
From 1,973 articles retrieved, 21 studies (9,296 patients) were included. Obesity was
associated with DGF (relative risk, 1.41; 95% confidence interval, 1.26–1.57; I2=8%;
Pheterogeneity=0.36), but not with acute rejection. Graft loss and death were associated with
obesity only in the analysis of studies that evaluated patients who received a kidney graft
before year 2000. No association of obesity with graft loss and death was found in the
analysis of studies that evaluated patients who received a kidney graft after year 2000. Death
by CVD was associated with obesity (relative risk, 2.07; 95% confidence interval, 1.17–3.64;
I2=0%; Pheterogeneity=0.59); however, most studies included in this analysis evaluated patients
who received a kidney graft after year 2000.
Conclusion
In conclusion, obese patients have increased risk for DGF. In the past years, obesity was a
risk factor for graft loss, death by CVD, and all-cause mortality. However, for the obese
transplanted patient today, the graft and patient survival is the same as that of the nonobese
patient.
COMMENTS
Previous data have linked obesity to poor outcomes in kidney transplant recipients. Among
them, a higher incidence of delayed graft function (DGF), acute rejection, and lower patient
and graft survival have been described . On the opposite, obesity seems protective in
hemodialysis.
To better understand the association between obesity and kidney transplantation outcomes,
the authors performed a systematic review with meta-analysis of observational studies that
included obese and nonobese recipients of a kidney transplant and appropriately reported
follow-up and outcomes.
The analysis showed that pretransplantation obesity is associated with DGF. The impact of
obesity on graft loss, death by CVD, and all-cause mortality depends on the era of
transplantation. No association was found between obesity and acute rejection.
In the present meta-analysis, it was not possible to evaluate the effects of a BMI greater than
40 kg/m2 on outcomes after kidney transplantation because only one study reported this BMI
stratification. The analysis of the effect of BMI equal to greater than 35 kg/m 2 was also not
applied because only two studies reported the number of patients in this group.
Nevertheless, a meta-regression analysis with the mean BMI revealed no significant results.
The reasons for the lack of influence of obesity in more recent cohorts are not entirely clear.
It is conceivable that it can be explained by the advances in immunosuppressive therapy
along with the improvement in general medical practice exemplified by better control of
comorbidities such as lipid disorders, hypertension, diabetes, cardiac conditions, and others
and the gain of experience in kidney transplantation.
Obesity should not on its own preclude a patient from being considered for kidney
transplantation. Other characteristics, such as age, cardiovascular status, diabetes mellitus,
other comorbidities, quality of dialysis, and the desire of the patient, must be considered in
this complex equation.
Pr. Jacques CHANARD
Professor of Nephrology