Nutrition 411: Nutrition for the Patient with Chronic Kidney Disease and Wounds

  Chronic kidney disease (CKD) is a condition in which the kidneys are damaged and cannot filter blood as well as possible. This damage can cause waste to build up in the body and lead to other health problems, including cardiovascular disease (CVD), anemia, and bone disease. CKD affects more than 20 million people (ie, more than 10% of the population) aged 20 years or older in the US.¹ People with early CKD tend not to feel any symptoms. The only ways to detect CKD are through a blood test to estimate kidney function and a urine test to assess kidney damage. Diabetes is a strong risk factor for developing CKD.

  CKD is usually irreversible and progressive; if it is not treated, over time it can lead to kidney failure, also called end-stage renal disease (ESRD). Once detected, CKD can be managed through medication and lifestyle changes to slow down the disease progression and to prevent or delay the onset of kidney failure. However, the only treatment options for kidney failure are dialysis or a kidney transplant.¹ For registered dietitians (RDs), some of the most challenging patients are those with CKD, because the lifestyle modification involves teaching the patient multiple dietary changes. When the same patient also has diabetes and/or a chronic wound, the diet becomes even more complex as a balance between nutritional requirements for each condition is sought. When treating these patients, it quickly becomes evident that what is prescribed for preserving kidney function is often at odds with what is prescribed to enhance wound healing. The question then becomes how to balance the medical nutrition therapy to ensure the best possible outcome for the patient.

Chronic Kidney Disease Classification

  Kidney function is sometimes expressed as the glomerular filtration rate (GFR). Normal GFR is 90–130 mL/minute. Urea is a product from the metabolism of protein. Normal kidneys maintain a blood urea nitrogen (BUN) range of 5–25 mg/dL. When the kidneys begin to fail to eliminate urea in the urine, urea will build up in the blood.

  The five stages of kidney disease are:
    Stage 1—GFR >90 mL/minute, with persistent protein in the urine;
    Stage 2—GFR 60–89 mL/minute, with persistent protein in the urine (mild disease);
    Stage 3—GFR 30–59 mL/minute (moderate disease);
    Stage 4—GFR 15–29 (severe disease);
    Stage 5—GFR <15 or individual is on dialysis (kidney failure).

  Diet intervention often is related to the stage of CKD, so it is important to know the patient’s stage of kidney disease.

Chronic Kidney Disease Diet Modifications

  Although a CKD diet involves general principles, each patient requires an individualized diet prescription based on the stage of the disease and the patient’s weight, symptoms, activity level, other medical problems, and goals. The general diet focuses on limiting fluids; eating a low-protein diet; restricting sodium, potassium, phosphorous, and other electrolytes; and getting enough calories if unintended weight loss is a problem. The expertise of an RD specializing in renal disease is necessary to individualize the diet to each patient’s unique medical situation. General guidelines are described below but should not be utilized as a substitute for professional advice.

  Calories. The number of calories prescribed is aimed at keeping the patient at a healthy weight, typically between 30 and 35 kcals/kg of body weight. Patients with diabetes or obesity may need a different amount of calories. Table 1 lists low-calorie, kidney friendly snacks. This list offers many creative solutions for patients who may feel unduly restricted by their dietary limitations.

  Protein. The human body needs protein every day for growth, building muscles, and tissue repair. In patients with wounds, increasing the amount of protein in the diet is routinely recommended. Patients with CKD may need to reduce the amount of protein consumed to avoid a buildup of urea in the body. Protein is usually not restricted until stage 3 or 4 CKD. Recommendations vary, but typically range from 0.6 g/kg–0.75 g/kg of body weight. For comparison, the protein recommendation for healthy adults is 0.8 g/kg of body weight, and that is often increased to 1.2–1.5 g/kg for patients with chronic wounds.

  Sodium. High-sodium foods may increase blood pressure and cause fluid retention. High blood pressure is one of the major causes of kidney diseases, so it is important to achieve and maintain blood pressure goals. A combination of medications and dietary intervention usually is prescribed. Patients should be instructed to avoid the following high-sodium foods: salt, bacon, ham, corned beef, pepperoni, sausage, pizza, Chinese food, fast food, pickles, cheese, soy sauce, canned soups, potato chips, and corn chips.

  Potassium. Potassium plays a role in keeping a steady heartbeat and proper muscle function. Although healthy kidneys keep the right amount of potassium in the body, patients with CKD may have to limit the amount of potassium in their diet. If potassium levels become too high, the patient may experience weakness, numbness, and tingling; at extreme levels, it can cause an irregular heartbeat or a heart attack.³ Learning which foods are high and low in potassium is critical. Techniques such as leaching can reduce the amount of potassium in certain vegetables. The following commonly consumed foods are high in potassium: bananas, oranges, orange juice, milk, prunes, prune juice, tomato juice, tomato sauce, nuts, chocolate, dried peas and beans, and salt substitutes.

  Phosphorus. Phosphorus is a mineral found in almost all foods. Normal kidneys will balance the amount of phosphorus in the body. When the kidneys fail to eliminate phosphorus in the urine, phosphorus increases in the blood. Extra phosphorus causes body changes that pull calcium out of the bones, making them weak. High phosphorus and calcium levels also lead to dangerous calcium deposits in blood vessels, lungs, eyes, and heart. This may begin as early as stage 3 CKD. When this occurs, it becomes necessary to limit and/or avoid high-phosphorus foods. In addition to dietary intervention, many patients are prescribed phosphate binders, taken with meals, to bind the phosphorus in the food and eliminate it in the stool. Some high-phosphorus foods to eliminate include: milk (all kinds), beans (red, black, and white), black-eyed peas, lima beans, nuts, chocolate, yogurt, cheese, liver, sardines, colas, and desserts made with milk.

  Fluids. In the early stages of CKD, patients usually are allowed to consume normal amounts of fluids. However, this must be individualized based on edema, urine output, and overall condition.

  Vitamins and minerals. Vitamin supplements may be prescribed for patients with CKD for a variety of reasons. CKD changes the body’s ability to make some vitamins, such as vitamin D. The waste products that build up in the body each day can change the way the body uses vitamins and minerals as can certain medications. It is also possible that by simply following the CKD diet, the patient may miss some vitamins and minerals by eliminating certain foods.

  CKD patients have greater requirements for some water-soluble vitamins. Special renal vitamins are usually prescribed to patients to provide the extra water soluble vitamins needed. Renal vitamins contain vitamins B₁, B₂, B₆, B₁₂, folic acid, niacin, pantothenic acid, biotin, and a small dose of vitamin C.⁴ Vitamin C supplements are recommended in a 60–100 mg dose. There is concern that taking high doses of vitamin C can cause a build up of oxalate, which can be deposited in the bones and soft tissues in patients with CKD.

Putting It All Together

  Medical nutrition therapy for the patient with chronic wounds usually involves increased amounts of protein and, often, vitamins. These recommendations are the exact opposite of the diet prescribed for advanced stage CKD patients who need to restrict protein and certain vitamins. How does the practitioner reconcile this divide? A frank discussion with the patient is a good starting point. The goal of the CKD diet is to preserve renal function for as long as possible to avoid dialysis. If dialysis is an unavoidable treatment in the near future and the patient is accepting of this, treating the wound aggressively with diet is the proper course of action. If the patient is determined to avoid dialysis, treatment should support this decision and protein should be limited despite the usual recommendations for wound healing. In these medically complex cases, taking time to educate the patient and his/her family on the risks and benefits of each alternative is critical. Once that is accomplished, the practitioner can take cues from the patient and plan the appropriate medical nutrition therapy.

 Nancy Collins, PhD, RD, LD/N, FAPWCA, is founder and executive director of RD411.com and Wounds411.com. For the past 20 years, she has served as a consultant to healthcare institutions and as a medico-legal expert to law firms involved in healthcare litigation. Correspondence may be sent to Dr. Collins at NCtheRD@aol.com. This article was not subject to the Ostomy Wound Management peer-review process.

1. Centers for Disease Control and Prevention. National Chronic Kidney Disease Fact Sheet: General Information and National Estimates on Chronic Kidney Disease in the United States, 2010. Atlanta, GA: US Department of Health and Human Services, CDC; 2010.

2. National Kidney Foundation. KDOQI Clinical Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification, and Stratification. 2002. Available at www.kidney.org/professionals/kdoqi/guidelines_ckd/p4_class_g1.htm. Accessed August 20, 2011.

3. National Kidney Foundation. Potassium and Your CKD Diet. 2011. Available at www.kidney.org/atoz/content/potassium.cfm. Accessed August 20, 2011.

4. Davita. The ABCs of Vitamins for Kidney Patients. Available at www.davita.com/kidney-disease/diet-and-nutrition/diet-basics/the-abcs-of-vitamins-for-kidney-patients/e/5311. Accessed August 20, 2011.