Both pre-dialysis CKD patients and dialysis patients may be eligible to receive a kidney transplant. For those who do receive a transplant, malnutrition may result in impaired surgical wound healing and higher rates of post-surgical infections (Transplant Proc. 2004;36:1650-1654).
Therefore, proper nutritional assessment is necessary to identify any signs of macro- or micronutrient depletion. In both pre-dialysis and dialysis patients, a daily kidney-specific multivitamin supplement is advisable due to restrictions in diet, drug-nutrient interactions, and possible metabolic aberrations from the kidney disease itself. Decisions about whether to supplement or restrict nutrients should be made on an individual basis similar to the approach used for CKD patients not being considered for a kidney transplant.
Advise weight loss cautiously
As in the general population, the CKD population has an increasing proportion of patients who are overweight or obese. Nutritional deficiencies are often masked by the presence of excessive somatic stores, so care must be taken to assess lean body mass, visceral protein status, and micronutrient status in these patients. It is common for transplant centers to have specific eligibility requirements for kidney transplantation, such as a certain body mass index (BMI).
Historically, it was thought that overweight or obese patients have worse outcomes in terms of surgical wound healing and infection rates. In fact, a recent single center, retrospective analysis conducted in Asia found that obesity was a significant predictor of graft rejection in kidney transplant recipients (Nephrology. 2010;15:259-265). These findings were similar to those from a retrospective analysis conducted at the University of Michigan in Ann Arbor, which found that obesity (BMI greater than 30 kg/m2) was associated with an increase in surgical site infections.
However, the study also showed that obesity had no independent effect on graft or patient outcome (Ann Surg. 2009;250:1017-1020). Given the high risk of mortality associated with weight loss in patients at later stages of CKD or those on dialysis, great caution should be used when recommending that patients lose weight. Patients with a BMI greater than 35 may benefit from an increase in physical activity to promote a better quality of life, as exercise may result in loss of fat mass with retention of lean body mass.
Protein and energy intake
Protein and energy requirements should be assessed on an individual basis with special consideration given to catabolic conditions that may increase patient nutritional needs, such as infections, gastrointestinal symptoms like diarrhea or vomiting, and comorbidities such as ulcerative colitis or HIV infection. In a pre-dialysis patient without a catabolic condition, a protein restriction of 0.6 g/kg body weight/day (2/3 high biological value protein) in conjunction with high energy intake (35 kcal/kg body weight/day) should be prescribed (Clin Nutr. 2006;25:295-310).
Dialysis patients should have a diet prescription which promotes anabolism through adequate kcal intake (30-35 kcal/kg body weight/day), and protein intake (1.2 g/kg body weight/day or more). If possible, physical activity while the patient is on dialysis or between dialysis sessions may be beneficial in optimizing nutrition status. Biochemical indices such as pre-albumin and albumin, and anthropometric measures such as weight change, BMI, and mid-arm muscle circumference, and global indices such as Subjective Global Assessment should be used to monitor patients for optimal nutritional status.
Following a kidney transplant, the goals for nutrition care are to promote wound healing, reduce infections, and combat the adverse effects of post-transplant medications. Thus, a diet that is high in protein and contains adequate energy to spare protein (1.3-2.0 g protein/kg body weight/day and 30-35 kcal/kg body weight/day) should be prescribed.
As in the pre-transplant period, a daily multivitamin supplement meeting the dietary reference intake recommendations may be beneficial. Serum phosphorus levels frequently drop post-transplant so blood values need to be carefully monitored in case supplementation is necessary.
Weight gain is common post-transplant. Excess weight gains may contribute to increased risk of cardiovascular death and diabetes. Therefore, promoting healthy heart habits such as eating monounsaturated fats, legumes and nuts, and high-fiber foods may be beneficial in lowering the risk of these comorbidities.
In conclusion, nutritional care in renal transplant patients must be provided with careful consideration to both the macro- and micronutrient needs of individual patients based on their assessed requirements. Promoting anabolic conditions prior to transplantation may lower the risk of complications after surgery, and weight maintenance post-transplant may reduce the risk of additional comorbidities.