Chronic kidney disease encompasses multiple kidney abnormalities, whether one or more are present, resulting in decreased renal function for three months or longer. One of the most important jobs of the kidneys is to filter waste products from the blood. The glomerulus, consisting of a cluster of tiny capillaries, is the part of the kidney that performs this filtration process. The glomerular filtration rate (GFR) reflects the rate at which kidneys filter the blood, indicating the stage of chronic kidney disease (CKD), and it is calculated using creatinine (Cr). Cr is a byproduct of creatine metabolism. GFR decreases as CKD progresses. All five stages are explained below, however this article provides nutritional guidelines for renal failure.

There are several key nutrients of concern with ESRD, therefore a proper diet is crucial to management of this chronic condition. These nutrients are protein, sodium, potassium, phosphorus, and fluid.

Contrary to the low requirements in earlier stages of kidney disease, increased protein is advised in ESRD due to losses during dialysis. High biological value proteins - poultry, beef, pork, fish, eggs, milk, quinoa, and soybeans - are recommended as they retain more nitrogen and cause less urea production. Urea is a byproduct of protein that in high levels can be toxic. The downside of these high biological value protein sources is they usually contain relatively high levels of phosphorus. Conversely, lower biological value proteins found in grains, dried beans, peas, and nuts are lower in phosphorus but produce more urea because of their incomplete amino acid profiles. In absence of other chronic conditions, such as diabetes mellitus, protein is the macronutrient of most concern. It is also important to ensure adequate calories are consumed. If caloric intake is below requirements, protein may be used for energy and lead to muscle wasting and protein-calorie malnutrition. In this case, nutritional supplementation is advised. General recommendations for protein intake are 1.0-1.2g/kg for hemodialysis patients and 1.2-1.5g/kg for peritoneal dialysis patients.

Sodium is a mineral occurring naturally in most foods and an electrolyte with multiple functions, including the regulations of blood volume, blood pressure, acid-base balance, muscle contraction, nerve activity, and the retention and elimination of fluid. Sodium is a vital nutrient, however it can build up to harmful levels in individuals with renal failure due to reduced glomerular function. Too much sodium in the blood, hypernatremia, may cause high blood pressure, edema in the extremities and face, congestive heart failure, and shortness of breath. An appropriate intake of sodium for most ESRD patients to prevent hypernatremia and its dangerous consequences is between 750 and 1000 milligrams (mg) per day.

Potassium is another mineral and electrolyte, essential for maintaining fluid and electrolyte balance, keeping heart rate regular, and supporting proper nerve transmission and muscle contraction. Hyperkalemia, high potassium levels in the blood, ensues when the kidneys are unable to effectively flush out excess potassium via urine, and it can lead to life-threatening cardiac arrhythmias, paralysis, muscle weakness, heart attacks, and death. Potassium is generally limited to <2400mg in those with ESRD, however restrictions also depend on serum levels measured by routine blood testing.

Phosphorus is a mineral that along with calcium is critical to building strong teeth and bones. It also plays a role in muscle movement and energy storage. Healthy kidneys maintain an appropriate balance of phosphorus and calcium in the blood. The build-up of phosphorus that occurs with impaired blood filtration causes calcium to be pulled from the bones in effort to restore that balance in the blood. Bones become weak and are more prone to breaking without adequate calcium. This calcium in the blood may also bind with phosphorus and form calcium deposits that settle in the blood vessels, heart, joints, muscles, and skin, reducing blood circulation, damaging organs, and causing pain. In early kidney disease, phosphorus restriction is rarely required. In ESRD, 800-1000mg is the upper limit for consumption, and a phosphate binder may also be prescribed. This binder is taken with food and works to eliminate excess phosphorus from the digestive tract in the stool, before it can be absorbed into the blood.

Fluid overload may occur in kidney failure, as the kidneys are unable to remove excess fluid. The potential outcomes of fluid overload are high blood pressure, edema in the extremities and face, cardiac problems, and shortness of breath. The amount of fluid allotted is dependent on urine output. Most physicians will prescribe 500 to 700 milliliters (ml) above the amount of urine output to account for losses from the lungs and skin. They also may consider any weight variances between dialysis days to determine a proper fluid prescription. Peritoneal dialysis patients usually can safely consume more fluid since they are dialyzed more frequently. Cyclic peritoneal dialysis patients are generally allotted urine output plus 1000 ml daily, while continuous ambulatory peritoneal dialysis patients may require 2000 ml above urine output per day.

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Reference the Download ⬇️ above for a visual chart that breaks down GFR range based on CKD stage.

Next Step: Estimate Calorie Requirements

35 kilocalories/kilogram (kcals/kg) for patients under 60 years of age with a normal body mass index (BMI)
30-35 kcals/kg for patients 60 years and older with a normal BMI
23-25 kcals/kg for obese patients
40-50 kcals/kg for underweight patients or those under severe stress