BOSTON — Obese patients remain much longer on waiting lists for kidneys and livers from deceased donors and have higher mortality than do nonobese individuals, Dr. Dorry L. Segev reported at the 2006 World Transplant Congress.
The increasing rate of obesity in the general population is mirrored by high rates of obese patients on waiting lists for kidney and liver transplants, said Dr. Segev of the department of surgery at Johns Hopkins University, Baltimore.
About 8% of patients on the United Network for Organ Sharing (UNOS) waiting list for a deceased donor liver and 7% of those waiting for a kidney have a body mass index (kg/m
In his study of 166,063 patients on the UNOS waiting list for a primary deceased-donor kidney transplant during 1995–2005, patients in BMI categories ranging from normal to morbidly obese benefited equally from transplantation, compared with patients in each BMI category who remained on the waiting list. These results suggested there might be a bias against renal transplantation in obese patients, he said.
The percentage of patients who received a deceased-donor kidney transplant during the study period declined significantly in a stepwise manner from a high of 44% in patients with the lowest BMI (18.5–25) to a low of 31% in those with the highest BMI (40 or greater). Those in the highest BMI category were 40% less likely to receive a kidney transplant than were patients in the lowest BMI range.
The mean waiting time to receipt of transplant similarly rose, from a low of 41 months in the lowest BMI group to a high of 65 months in the highest BMI group.
As BMI increased, patients had significantly higher rates of delayed graft function. But kidney transplant recipients with a BMI of 40 or greater had only modestly lower rates of graft survival at 5 years (75%) and patient survival at 5 years (78%) than did normal BMI patients (80% and 83%, respectively).
The obese patients who were called in for a kidney transplant may have been a selected group that had better outcomes than an unselected group would have had. But if the obese patients who “were not called in were not appropriate for transplantation, perhaps we should never have listed them in the first place,” Dr. Segev said at the congress, which was sponsored by the American Society of Transplant Surgeons, the American Society of Transplantation, and the Transplantation Society.
In the time since the Model for End-Stage Liver Disease (MELD) score was introduced in 2002 to allocate deceased donor livers to patients on the UNOS waiting list, obese patients with a MELD score less than 20 have been less likely than nonobese patients to be listed, to be transplanted once listed, or to receive a transplant in exception to their MELD score, Dr. Segev reported in a separate presentation.
In a review of the 30,968 patients placed on the UNOS waiting list for a deceased-donor liver since 2002, Dr. Segev and his associates found that as BMI increased, patients were less likely to be listed and transplanted at centers. Of patients with a BMI of 18.5–34.9, 100% were listed and 100% were transplanted. But among those with a BMI of 35–39.9, 83% were listed and 78% were transplanted. In patients with a BMI of 40 or greater, 74% were listed and 53% were transplanted. This trend nearly disappeared, however, when the analysis was limited to high-volume centers.
A BMI of 40 or greater was an independent risk factor for a longer wait for a liver transplant, but not for graft loss or for patient death after transplantation.
In patients with a MELD score of less than 15, those with a BMI of 40 or greater spent significantly more time on the waiting list than did those with a BMI of 35–39.9. The same trend was true for recipients with a MELD score of 15–20, though all of the BMI subgroups with this severity of liver disease got transplanted faster than those with a MELD score of less than 15. Among all the BMI categories, there was no difference in the time to transplantation in patients with a MELD score greater than 20.
A significantly smaller percentage of patients in the highest BMI category received an exception to their MELD score than did patients in the lowest BMI category. This left those with a BMI of 40 or greater 35% less likely to receive an exception to their MELD score.
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