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Spring 1997Volume 4, Number 1 |
The prevalence of obesity among Americans is increasing (see table for definitions). A review of four national health surveys completed between 1960 (National Health Examination Survey) and 1991 (National Health & Nutrition Examination Survey III) revealed that the rate of obesity in adults had increased from 24% to to 33% of the population during this interval.1 Although many transplant candidates are underweight and malnourished, the prevalence of obesity among individuals requiring transplantation appears to be increasing. Surgical risks associated with obesity include wound sepsis, respiratory and cardiovascular complications, and thromboembolic disorders.2-4 Because of these potential complications, some surgeons are reluctant to transplant severely obese patients.
| Obesity
According to Percent Desirable Body Weight (%DBW) and Body Mass Index (BMI) Standards | |||
| Classification | Percent DBW | BMI - Male (kg/m2) | BMI - Female (kg/m2) |
| Acceptable weight | 100% | 20.7 - 27.7 | 19.1 - 27.2 |
| Overweight | >120% | 27.8 - 31.0 | 27.3 - 32.2 |
| Severely overweight | >140% | 31.1 - 45.3 | 32.3 - 44.7 |
| Morbidly obese | >200% or 100 lbs. | >45.4 | >44.8 over DBW |
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DBW = body weight divided by the midpoint of a desirable weight for a person of the same frame; desirable weights usually are obtained from the 1959 or 1983 Metropolitan Life Insurance Company tables BMI = body weight in kg divided by height in m2; although BMI estimates total body mass, it correlates well with the amount of body fat and is preferred over percent of relative weight standards | |||
To determine if obesity is associated with complications after transplantation, researchers have compared posttransplant outcomes of obese renal and liver transplant recipients to outcomes of nonobese patients. Holley et al5 compared 46 obese (BMI >30) to 50 nonobese renal transplant patients. Obese patients had an inferior patient survival rate (89% vs 98%), one-year graft survival rate (66% vs 84%), and incidence of immediate graft function (38% vs 64%) compared with their nonobese counterparts. In addition, obese patients had significantly higher rates of wound complications (20% vs 2%), intensive care unit admissions (10% vs 2%), ventilator reintubations (16% vs 2%), and new onset of diabetes mellitus (12% vs 0%) compared with nonobese patients.
Merion et al6 also evaluated the effect of pretransplant obesity on outcome after renal transplantation. Forty of 263 renal transplant patients were identified as obese (>120% of ideal weight). The incidence of wound infections was higher in obese patients (17.5% vs 6.3%), but length of hospitalization, rejection episodes, patient survival rates, and graft survival rates were not significantly different compared with nonobese transplant recipients. Pretransplant weight correlated with posttransplant weight gain; obese patients gained an average of 5.3 kg more than nonobese patients during the first posttransplant year.
A third study by Gill et al7 compared 85 renal transplant patients with a BMI >30 to 85 matched patients with a BMI <27. Five-year patient and graft survivals were reduced in the obese patients (55% patient survival, 42% graft survival) compared with the nonobese controls (90% patient survival, 66% graft survival). In addition, the obese patients averaged 3.8 complications (wound complications, leg ulcers, recent onset diabetes, phlebitis, hypertension, sleep apnea, and gastrointestinal complications) per patient compared with 2.4 per nonobese patient. This study found no difference in one-year weight gain between the two groups.
Finally, Pirsch et al8 compared 59 mildly obese (BMI = 27.5 to 30) and 59 obese (BMI >30) renal transplant patients to 466 nonobese (BMI <27.5) renal transplant patients. Urologic and wound complications were significantly greater in obese patients than in nonobese patients. Nonobese patients had a 1% rate of urologic complications, 2% wound infection rate, and 9% incidence of delayed graft function. This compared with 3%, 7%, and 8% incidence, respectively, in the mildly obese patients and 5%, 8%, and 27% incidence in obese patients. Additionally, patients with a BMI >30 experienced delayed graft function more often and had greater immunologic graft loss than those with a lower BMI.
Pretransplant obesity also has been evaluated in the liver transplant population, but with less clearcut results than in the renal transplant studies. Keefe et al9 evaluated outcomes in 18 obese liver transplant recipients. Five patients were severely obese (BMI = 33.2 to 34.6) and 13 were morbidly obese (BMI = 36 to 48). The researchers assessed the incidence of complications but did not compare them to complication rates in their nonobese patients. Wound infection occurred in 61% of the 18 obese patients, and two patients required reoperation for wound infections. Insulin-requiring diabetes occurred in two patients, and mean weight gain was 2 kg during the 16.7-month follow-up period. The researchers commented that hypertension was common but did not report an occurrence rate.
A study at our own center retrospectively compared 298 liver transplant patients with a BMI <27.5 to 92 recipients with a BMI >27.5.10 There were no differences between the groups in infection rate, rejection rate, duration of ventilatory support, or length of hospital stay. The only significant finding was that severely obese patients required longer intensive care unit stays than the nonobese group.
| Therefore, if an obese individual requires organ transplantation but can be sustained with medical therapy while awaiting transplantation, weight loss under the supervision of a Registered Dietitian should be encouraged. |
In summary, studies suggest that pretransplant obesity is an independent risk factor for posttransplant complications and graft survival in renal transplant recipients. Based on available studies, the same conclusion cannot be made regarding transplantation in obese liver transplant candidates. Despite some studies which showed no increased risks in obese liver transplant patients, no study has shown that obesity is beneficial for posttransplant recovery. Therefore, if an obese individual requires organ transplantation but can be sustained with medical therapy while awaiting transplantation, weight loss under the supervision of a Registered Dietitian should be encouraged. On the other hand, if no life-saving measures other than transplantation are available for a severely obese patient, obesity alone probably should not preclude transplantation.
Jeanette Hasse, PhD, RD
Baylor Institute of Transplantation Sciences
Baylor University Medical Center
Dallas, Texas
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