Kidney Transplant Survival Benefit Similar for Obese, Lean Patients

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Kidney Transplant Survival Benefit Similar for Obese, Lean Patients

By: MITCHEL L. ZOLER, Internal Medicine News Digital Network
06/01/11

PHILADELPHIA (EGMN) – Morbidly obese patients with a body mass index of 40 mg/m2 or greater respond to kidney transplants as well as do ideal-weight patients, based on a review of 120,000 U.S. kidney transplant patients who received their organs during 1996-2009.

"The survival benefit of a kidney transplant is no different for morbidly obese and for ... ideal-weight patients," Dr. Roberto Kalil said at the American Transplant Congress, which was sponsored by the American Society of Transplant Surgeons. In both BMI categories, kidney transplants led to an average 45% reduction in the subsequent mortality risk, said Dr. Kalil, a nephrologist and kidney transplant physician at the University of Iowa in Iowa City.

"BMI is not a critical issue," agreed Dr. Lawrence G. Hunsicker, a professor of medicine at Iowa and a coauthor of the study. "You still need to evaluate each morbidly obese patient as a candidate for surgery and as a candidate for kidney transplant, as you would any patient. But should surgeons use BMI as a criterion for surgery? Probably not," Dr. Hunsicker said in an interview.

"BMI is a very imperfect parameter" for judging a patient’s suitability for transplant, added Dr. Kalil.

Despite this finding, many surgeons and transplant programs deny kidney transplants to morbidly obese patients, and many programs have a BMI ceiling for allowing transplants.

"Most centers do not accept patients for kidney transplant with a BMI of 35" or higher, noted Dr. Ignatius Y.S. Tang, a nephrologist and transplant physician at the University of Illinois in Chicago. Even the University of Iowa, where until recently Dr. Hunsicker served as medical director of organ transplantation, has a policy of not placing kidney transplants in patients with a BMI of 40 or higher. "I don’t think that’s right," Dr. Hunsicker said. Transplant centers apply BMI cutoffs individually, and the United Network for Organ Sharing (UNOS) has no blanket U.S. policy, he noted.

The findings reported by Dr. Kalil used data on 237,537 U.S. patients aged 18 years or older who were listed for a first kidney transplant with UNOS during 1996-2009. The group included 8,382 patients with a BMI of 40 or greater (4%). Among these morbidly obese patients, 2,581 actually received a transplant, which accounted for 2% of the more than 120,000 total U.S. patients who received a kidney transplant during the 14-year period examined.

In an analysis that controlled for age, sex, race and ethnicity, diabetes, blood type, listing priority, and type of health insurance, a kidney transplant improved the survival rate among morbidly obese patients by 48%, compared with the survival of morbidly obese patients who did not receive a transplant – similar to the 45% improvement seen in ideal-weight patients, and similar to the survival benefit seen in every other BMI subgroup. Dr. Kalil reported.

The finding carries one important caveat: The analysis could assess the outcomes of only the morbidly obese patients whose physicians decided to add them to the UNOS kidney waiting list. So the findings may represent exceptional, low-risk morbidly obese patients. "I think that’s unlikely, because generally the decision to list these patients or not depends on a center’s policy," said Dr. Hunsicker. "I think some centers listed these patients and others did not. I think the selection was by centers, not by patients," he said.

Additional, BMI-based analyses of the UNOS data showed that the listed morbidly obese patients had a statistically significant (26%) reduced chance of receiving a kidney transplant, compared with ideal-weight patients. Listed patients with a BMI of 40 or greater formed the only BMI subgroup with a significantly different transplantation rate.

The analysis also showed that patients who started with a BMI of 40 or more at the time they first appeared on the UNOS kidney transplant list lost an average index value of 4.7 in the period before they actually received a transplant. However, the change in BMI prior to transplantation had no relationship to the graft survival following transplantation, Dr. Kalil said. Waiting for patients to lose weight before proceeding with a transplant "was not associated with decreased mortality, and it wasted time," Dr. Hunsicker said. The better approach is to proceed with the transplant as soon as possible, he said.

Dr. Kalil, Dr. Hunsicker, and Dr. Tang all said that they had no disclosures.

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