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Medical Nutrition Therapy for Renal

Disorders

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Functions of the Kidney

Excretory

Acid-base balance

Endocrine

Fluid and electrolyte balance

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Excretory Functions

Removal of excess fluid and waste products

180 L of filtrate pass through the kidneys

each day producing 1-2 L of urine

Wastes excreted from the body in urine

include urea (byproduct of protein

metabolism); excess vitamins and minerals;

metabolites of some drugs and poisons

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Acid-Base Functions

Acid-base balance is maintained through a

buffer system, which maintains blood at pH

of 7.4

Bicarbonate Buffer.

Phosphate buffers intracellular fluid

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Endocrine Functions

1,25-dihydroxy-vitamin D3 or calcitriol is

produced in the kidney; enhances calcium

absorption

Activation of Vitamin D and excretion of

excess phosphate maintain healthy bones

Erythropoietin: acts on the bone marrow to

increase production of red blood cells

The Nephron

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The Most Common Kidney Diseases

Diabetic Nephropathy damage to the nephrons in

the kidneys from unused sugar in the blood,

usually due to Diabetes.

High Blood Pressure can damage the small blood

vessels in the kidneys. The damaged vessels

cannot filter poison from the blood as they are

supposed to.

Polycystic Kidney Disease (PKD) is a hereditary

kidney disease in which many cysts grow in the

kidneys. These cysts may lead to kidney failure.

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The Most Common Kidney Diseases

Acute Renal Failure - Sudden kidney failure caused by blood loss, drugs or poisons. If the kidneys are not seriously damaged, acute renal failure may be reversed.

Chronic Renal Failure - Gradual loss of kidney function is called Chronic Renal Failure or Chronic Renal Disease.

End-Stage Renal Disease - The condition of total or nearly total and permanent kidney failure.

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Kidney Diseases

Glomerular diseases

– Nephrotic syndrome

– Nephritic syndrome—tubular or

interstitial

Tubular defects

– Acute renal failure (ARF)

Other

– End-stage renal disease (ESRD)

– Kidney stones

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Nephrotic Syndrome

Albuminuria: more than 3 g/day urinary

albumin losses, with proportionally lesser

amounts for children

Hypoalbuminemia

Hypertension

Hyperlipidemia

Edema

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MNT in Nephrotic Syndrome

Protein 0.8 to 1 g/kg.

Sodium based on fluid status

Potassium and other minerals (calcium,

phosphorus) monitored and

individualized

Fluid unrestricted

Diet therapy probably not effective for

hyperlipidemia; may require medication

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Nephritic syndrome: Nutritional

Management

Diet to treat underlying disease

Restrict diet if necessary to control

symptoms

Protein restricted in uremia

Sodium restriction in hypertension

Potassium restriction in hyperkalemia

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Acute Renal Failure

Rapid, often reversible deterioration of

renal function

GFR declines over hours to days

Most commonly occurs during

hospitalization (5% of hospitalized pts; 30%

of ICU pts)

Associated with major in-hospital morbidity

and mortality (7 to 80%)

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Renal Replacement Therapies in ARF

Hemodialysis: standard treatment if patient

is hemodynamically stable

– However, risk of hypotension and wide swings

in body weight in unstable patients

Continuous hemofiltration provides slow,

continuous filtration across a membrane,

driven by arterial pressure.

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Renal Replacement Therapies in ARF

Continuous hemodialysis using ultrafiltrate

fluid similar to plasma

– Clearance occurs through diffusion from high

concentration (blood) to low concentration

Peritoneal dialysis: less often used, not as

effective when large volume or solute

clearances needed.

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MNT for Adult ARF

Energy: 1.2-1.3 or 25-35 kcal/kg

Protein: 0.8-1.2 g/kg without dialysis; 1.2-1.5 g/kg catabolic and/or initiation of dialysis

Fluid: 24 hour urine output + 500 ml (750-1500 ml)

Sodium: 2.0-3.0 grams

Potassium: 2.0-3.0 grams

Phosphorus: 8-15 mg/kg; may need binders; needs may increase with dialysis, return of kidney function, anabolism

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Nitrogen Balance in ARF

Standard nitrogen balance studies require a

creatinine clearance of more than 50

mL/min/1.73m2

In ARF, urea nitrogen appearance (UNA) is

a better method of determining nitrogen

balance.

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Chronic Kidney Disease

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Causes of Chronic Kidney Disease

Cause Incidence (%)

Diabetes 40

Hypertension 27

Glomerulonephritis 13

Interstitial disease 4

Renal cystic disease 3

Tumors 2

Other 10

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Medical Management

Dialysis

Immunosuppressant drugs

Kidney transplant

Psychological support

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Uremia, a Clinical Syndrome—

Signs and Symptoms Malaise

Weakness

Nausea and vomiting

Muscle cramps

Itching

Metallic taste (mouth)

Neurologic impairment

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MNT for CKD, HD, PDCKD Hemodialysis CAPD or CCPD

Protein 0.6-1.0 1.1-1.4 1.2-1.5g/kg/day

Energy 30-35 30-35 30-35

(kcal/kg IBW)

Phosphorus 8-12 indiv <17 indiv <17 indiv

(mg/kg IBW)

Sodium 1000-3000 2000-3000 2000-4000

(mg/d)

Potassium Individualized ~ 40 Individualized

(mg/kg IBW)

Fluid Unrestricted 500-750 + Individualized

(ml/d) urine output

(1000 if anuric)

Calcium Individualized Individualized Individualized

(mg/d) based on serum level ~1000 mg/day ~1000 mg/day

Use adjusted IBW if obese

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Nutrition Assessment and

Monitoring in the CKD Pt

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Anthropometric Measurements

% usual body weight (%UBW)

% standard body weight (%SBW)

Height

Skeletal frame size

BMI

Skinfold thickness

Mid-arm muscle area, circumference, or diameter

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Body Weight Assessment in CKD

Use dry weight or edema-free body weight

– In HD: post-dialysis weight

– In PD: weight after drainage of dialysate with peritoneum empty

In obese or very underweight people, use adjusted edema-free body weight

Adjusted EFBW=

BWef + [SBW*-BWef x .25]

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Blood Urea Nitrogen (BUN)

Measure of the nitrogenous waste products of protein

High BUN in CKD may reflect high protein intake, GI bleeding or inadequate dialysis, increased catabolism due to infection, surgery, poor nutrition

Decreased BUN may mean protein anabolism, overhydration, protein loss, low dietary protein

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Creatinine (normal 0.5-1.4 mg/dL)

Nitrogenous waste product of muscle metabolism

Produced proportionate to muscle mass

Unrelated to dietary protein intake (DPI)

Sensitive marker of renal function: the higher the

serum creatinine, the greater the loss of renal

function; may reflect inadequate dialysis or

muscle catabolism

A decrease in creatinine over time may reflect loss

of lean body mass

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Phosphorus (normal 3.5-5.5 mg/dL)

As renal function decreases, phos accumulates in

the blood

phos triggers release of PTH that releases

calcium from bone

Phos binders prevent phosphorus from being

absorbed in the gut; form insoluble compound so

phos is excreted in stool

Phos clearance poor in HD and CAPD

↓ phos may mean excess phos binder or poor p.o.

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Calcium (8.4-9.5 mg/dL)

Most abundant mineral in human body

Nearly half of calcium is bound to albumin; if serum calcium is low, evaluate albumin level; can correct for low albumin

Calcium-Phosphorus Product: multiply serum calcium x serum phos: if >55-75, calcification can occur

<2000 mg/day elemental calcium from diet + binders stage 3-4

High Ca+: calcification, nausea, vomiting, muscle twitching may mean too much Ca+ from meds or diet

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Serum Sodium (normall 133-145 mEq/L)

Not a reliable indicator of sodium intake in

CKD

Fluid retention due to decreased urine

production can dilute an elevated level

Serum levels must be evaluated in

conjunction with fluid status

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Lipids

Cardiovascular disease is the most common cause of death in people with CKD

Kidney disease is considered the equivalent of a risk factor, like diabetes

HD: often have normal LDL, TC, ↑triglycerides, ↓ HDL

PD: have ↑ LDL/TC + ↑ TG

Renal Tx: ↑ LDL/TC/TG, normal HDL, often due to medications

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Cholesterol in CKD

High • High risk TC 200-300 mg/dl (non-fasting)

• LDL goal < 100 mg/dl

Low • <150 -180, evaluate for pro-energy malnutrition

• Increased mortality

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Hematological Indicators

Hemoglobin: ↓ due to lack of erythropoetin,

produced by the kidney; pts receive

synthetic EPO tx (Epogen)

May have anemia of chronic disease

Ferritin: may be indicator of iron overload;

↑ ferritin may mean EPO resistance

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Glomerular Filtration Rate (GFR)

Best index of kidney function

Used to establish stage of CKD

GFR is the amount of filtrate formed per minute

based on total surface area available for filtration

(number of functioning glomeruli)

Can be determined using injected isotope (inulin)

measurement in urine

Can be calculated from serum creatinine using

standard equations

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Interdialytic Weight Gain

Pts on dialysis gain several kg of fluid

between HD treatments

If pts gain >5%, may reflect excessive fluid

intake, leading to hypertension, edema,

ascites, pleural effusion

Fluid gains of <2% reflect minimal fluid

and food intake, may be losing body mass

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Measures of Dialysis Adequacy

Urea Reduction Rate (URR)

Refers to change in urea concentration between

pre and post-dialysis blood tests

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Monitoring Nutrition Status in CKD

with GFR<12mL/min/1.73m2

Recommended measure Frequency

Serum albumin levels Every 3 months

Edema-free actual body

weight, % std wt, SGA

Every 1-3 months

nPNA or dietary

interviews and diaries

Every 3-4 months

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Pre-ESRD (DM)

Primary Prevention

– Glycemic control (DCCT)

• Aim for Euglycemia

• Watch for low B.S.

– B.P. control

• 130/80

• Na+ restrict

– Base on comorbidities (~2-3 g.)

– Medications may increase or decrease K+; monitor

• Wt. loss (gradual)/exercise

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MNT in Patients on Hemodialysis

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Hemodialysis

Removes concentrated molecules and

excess fluid from pts blood through

diffusion and ultrafiltration

Three parts of the system are the dialyzer

(artificial kidney), the dialysis machine, and

the dialysate

Requires vascular access, usually through

an AV (arteriovenous) fistula

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AV (arteriovenous) Fistula

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Nutritional Management

Prevent deficiencies

Control edema and serum electrolytes

Prevent renal osteodystrophy

Provide an attractive and palatable diet

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MNT in HD: Protein

10-12 g free amino acids lost per treatment

during dialysis

Greater amino acid losses with glucose-free

dialysate and high flux dialyzers

1.2 g protein/kg standard body weight

(SBW) with 50% high biological value

(meat, poultry, fish, eggs, soy, dairy)

Most HD patients take in less than 1 g/day

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MNT in HD: Energy

Adults <60 years: 35 kcal/kg SBW

Adults > 60 or obese: 30-35 kcals/kg body

weight

Actual intakes of HD patients in studies are

lower than that (mean 23 kcals/kg in HEMO

study)

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MNT in HD: Lipids

HD patients at risk for lipid disorders

Recommended fat intake<30% of calories

and saturated fat<10%; cholesterol <300

mg/day

Optimum fiber intake 20-25 g/day

These restrictions are difficult to achieve

along with other restrictions of HD diet

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MNT in HD: sodium and fluid

≥ 1 L fluid output: 2-4 g

Na and 2 L fluid

≤ 1 L fluid output: 2 g Na

and 1-1.5 L fluid

Anuria: 2 g Na and 1 L

fluid

Restrict Na+ if ↑

interdialytic wt gain, CHF,

edema, HTN, low serum

sodium

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MNT in HD: Potassium

Potassium needs related to urinary output

Most patients on HD can tolerate 2.5 g of K+

Stricter diet may be indicated for pts w/ insulin deficiency, metabolic acidosis, treated with beta blockers or aldosterone antagonists, hypercatabolic

Individuals: 40 mg/kg edema-free IBW or SBW

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MNT in HD: Phosphorus

Maintain s. phos 3.5-5.5 mg/dL

Usually ok until GFR ↓ to 20-30 mL/min

Dialysis removes 500-1000 mg/treatment

Use phosphorus binders with meals: absorb

50% of dietary phosphorus

Dietary intake: 800 to 1000 mg/day or <17

mg/kg IBW or SBW

Identify high protein, low phos food sources

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MNT in HD: Calcium

High from excess Ca++ type binders,

vitamin D analogs, Ca++ fortification

Goal 8.4-9.5 mg/dl.

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MNT in HD: Vitamins

H2O soluble vitamins

Dialyzable – take after H.D.

B vitamins and vitamin C in renal vitamin

↑ Vit. C → ↑ oxalate → calcification of soft tissues

and stones

Individualize need for:

– Fe++ (IV most common), Vitamin D, Ca++, Zinc.

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MNT in HD: Vitamin D

Vitamin D is activated in the kidney to

calcitriol, or vitamin D3

As D3 levels fall, calcium absorption ↓ and

phos excretion ↓

Vitamin D3 therapy helps prevent renal

bone disease but may cause hypercalcemia

Renal pts should use calcitriol supplements

under the supervision of a physician

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Hemodialysis

Typical diet order

– 2000 calorie, 80 g protein, 2 g Na+, 3 g K+,

low phosphorus, 1500 cc fluid restriction

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Skeletal Effects of Chronic

Renal Failure

Hyperphosphatemia

Hypocalcemia

Hyperparathyroidism

Low bone mass and density

Osteitis fibrosa cystica—hyperplastic

demineralized bone

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Monitor Patient Status

1. BP >140/90

2. Edema

3. Weight changes

4. Urine output

5. Urine analysis:

—Albumin

—Protein

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Monitor Patient Status (cont)

6. Kidney function

Creatinine clearance

Glomerular filtration rate (GFR)

7. Blood values

BUN 10 to 20 mg/dl (<100 mg/dl)

Creatinine 0.7 to 1.5 mg/dl (10-15 mg/dl)

Potassium 3.5 to 5.5 mEq/L

Phosphorus 3.0 to 4.5 mg/dl

Albumin 3.5-5.5 g/dl

Calcium 9-11 mg/dl

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Peritoneal Dialysis

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CAPD (continuous ambulatory

peritoneal dialysis)

Most patients do 4-5 exchanges per day

A specific volume of dialysate (1500-3000 ml) is infused into the peritoneal cavity via a catheter

The dialysate dwells for 4 hours as excess fluid and toxins diffuse through peritoneal membrane

Dialysate and wastes are drained from the body and the process repeated.

Dialysate is present in the body 24 hours per day

APD (automated peritoneal dialysis therapy) speeds the process

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MNT for PD: Energy

Energy: 35 kcals/kg/day SBW or adjusted

body weight for pts<60 years; 30 kcals/kg

for those >60

Calories provided in the dialysate should be

included in total intake (may absorb as

much as 1/3 of daily energy needs)

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MNT for PD: Protein

PD patients lose 5-15 grams of protein a

day, primarily as albumin

Goal 1.2-1.3 g/kg SBW or ABW/day

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MNT for PD: Sodium

PD clears sodium very well, so sodium can

be fairly liberal

However, high salt diets increase thirst and

may make adherence to fluid limits more

difficult

General recommendation is 2-4 grams

sodium

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MNT for PD

Potassium: is easily cleared by PD; some

patients may need K+ supplementation

Calcium: limit to 2000 mg elemental

calcium

– Generally pts get ~1500 mg from calcium-

based phosphate binders

– Serum calcium should be maintained in low

normal range (8.4-9.5 mg/dl)

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MNT for PD

Phosphorus: limited to 800-1000 mg/day

which is difficult with high protein diet

– Use phosphate binders

Fluid: can be adjusted by varying the

dextrose concentrations of the dialysate

– May need to be restricted if pts cannot achieve

fluid balance without frequent hypertonic

exchanges

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PD: weight gain,

hypertriglyceridemia, hyperglycemia

Increase exercise as allowed by MD

Limit sodium and fluid to minimize

hypertonic exchanges

Use solutions with alternate hypertonic

agents such as Icodextrin

Modify energy intake to facilitate wt loss

Modify intake of sugars and fats, especially

saturated fats

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PD: Protein Losses, Malnutrition

Patient education regarding protein goals and ways to meet them

Suggest pt eat protein foods first and limit fluids at mealtime

Frequent smaller portions of protein and easy to eat proteins such as egg white, cottage cheese, etc

Education on sterile technique to avoid peritonitis

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Food Groups Kcal CHO g. PRO g. FAT g. Na mg. K+ mg. PO4 mg.

Milk ( ½ c.) 85 6 4 5 80 185 110

Meat 65 0 7 4 25 100 65

Starch 80 15 2 1 80 35 35

Vegetable 25 5 1 0 15 150 20

Fruit 60 15 0.5 0 5 150 15

Fat (1TB.) 100 0 0 11 150 0 5

Calorie

Boosters

60 15 0 0 15 20 5

Beverages:

Coffee (1c.)

tea (1 bag)

0 0 0 0 0 100 0

RENAL EXCHANGES FOR MEAL PLANNING

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Protein Foods (65 kcals, 7 grams protein, 25 mg Na, 100 mg K+, 65 mg

phos)

Meat 1 ounce

Egg 1

Fish 1 ounce

Shellfish 1 ounce

Poultry 1 ounce

Egg substitutes ¼ c

Bacon 4 slices

Cheese 1 oz

Milk 1 cup

Nut butters 2 T

Cottage cheese ¼ cup

Lunchmeat 1 oz

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Milk Servings (2% milk) 85 kcals, 6 g CHO, 4 g pro, 5 g fat, 80 mg Na+, 185 mg K+, 110 mg Phos

½ cup milk

½ cup plain ice cream

½ cup yogurt

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Starch Servings80 kcal, 15 g CHO, 2 g pro, 1 g fat, 80 mg Na+, 35 mg K+, 35 mg PO4

Bread, white or rye 1 slice

Cake 2 in sq or cupcake

Plain cake donut 1

Cold cereal 1 cup

Dinner roll 1 small

Macaroni, noodles, rice ½ cup

Popcorn, unsalted, 1 cup

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Vegetable Servings25 kcal, 5 g CHO, 1 g pro, 15 g Na+, 150 mg K+, 20 mg PO4

Asparagus ½ cup

Green beans ½ cup

Cabbage ½ cup

Carrots ½ cup

Cauliflower ½ cup

Corn ½ cup

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Fruit Servings ↓ K+60 kcals, 15 g CHO, .5 g protein, 150 mg K+, 15 mg phos

Apple

Apple juice ½ c

Applesauce ½ c

Apricot nectar ½ c

Blackberries ½ c

Blueberries ½ c

Fruit cocktail ½ c

Grapes ½ c

Lemon

Lime

Peach

Pear

Pineapple

Plums (1)

Raspberries

Watermelon

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Fruit Servings (High potassium)60 kcals, 15 g CHO, .5 g protein, >250 mg K+, 15 mg phos

Apricots

Bananas

Dates

Honeydew melon

Kiwifruit

Nectarine

Orange

Orange Juice

Prune juice

Prunes

Raisins

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Fat Choice100 kcals, 11 g fat, 150 mg Na+, 5 mg PO4

Margarine/butter 1 T

Cream cheese 2 T

Mayonnaise 11/2 T

Non-dairy topping ½ cup

Sour cream ¼ cup

Vegetable oil 1 T

Tartar sauce 2 T

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Calorie Boosters60 kcals, 15 g CHO, 15 mg Na+, 20 mg K+, 5 mg PO4

Hard candy 4 pieces

Jam or jelly 2 T

Jelly beans 15

Honey 2 T

Sugar brown or white 2 T

Marshmallows 5 large

Fruit snacks and candies 1 oz

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Beverages100 mg K+ (also counts as fluid)

Coffee 1 cup

Tea 1 bag

Others16 oz

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Well Mr. Osborne, it may not be kidney stones after all.

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Kidney Stones1. Particulate matter crystallizes

Ca salts (Ca oxalate or Ca phosphate)

Uric acid

Cystine

Struvite (NH4, magnesium and phosphate)

2. Ca salts in stones—Rx: high fluid; evaluate calcium from diet; may need more!

3. Treat metabolic problem; low-oxalate diet may be needed; acid-ash diet is sometimes useful but not proven totally effective

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Acid-Ash Diet

Increases acidity of urine (contains chloride,

phosphorus, and sulfur)

Meats, cheese, grains emphasized

Fruits and vegetables limited (exceptions

are corn, lentils, cranberries, plums, prunes)

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Alkaline-Ash Diet

Increases alkalinity of urine (contains

sodium, potassium, calcium, and

magnesium)

Fruits and vegetables emphasized

(exceptions are corn, lentils, cranberries,

plums, prunes)

Meats and grains limited

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Summary

Renal diseases—delicate balance of

nutrients

Regular monitoring of lab values, with

altered dietary interventions accordingly