Chapter 22 Nutrition and Renal Diseases

Nutrition and
Renal Diseases
2222
Copyright © 2017 Cengage Learning. All Rights Reserved.

© Cengage Learning 2017
Introduction
• Kidneys
– Filter the blood and remove excess fluid and
wastes for elimination in urine
– Nephron: functional unit of the kidney
• Glomerulus: filters water and solutes from the
blood
• Bowman’s capsule: surrounds the glomerulus;
collects the filtrate that is passed to the tubules

Introduction (cont’d.)
• Kidneys
– Regulate the extracellular fluid volume
• Control osmolarity, electrolyte concentrations, and
acid-base balance
– Excrete metabolic waste products
• Urea and creatinine; various drugs and toxins
– Secrete renin, produce erythropoietin, and
convert vitamin D to active form

The Kidneys and Nephron Function

Nephrotic Syndrome
• Syndrome caused by significant
proteinuria (>3-3.5 g/day)
– Damage to glomeruli increases their
permeability to plasma proteins
• Causes
– Glomerular disorders, diabetic nephropathy,
immunological and hereditary diseases,
infections (kidney or other), etc.

Nephrotic Syndrome (cont’d.)
• Consequences of nephrotic syndrome
– Attempting to compensate, liver increases
synthesis of various plasma proteins
• Some or the proteins produced in excess
– Edema
• Hypoalbuminemia: contributes to a fluid shift from
blood plasma to the interstitial spaces
• Impaired sodium excretion: sodium and water
retention

• Consequences of nephrotic syndrome
– Blood lipid and blood clotting abnormalities
• Elevated levels of LDL, VLDL, and lipoprotein(a)
• Increased risk of deep vein thrombosis
– Other effects of nephrotic syndrome
• Susceptibility to infection
• Increased risk of rickets (children)
• PEM and muscle wasting

Effects of Urinary Protein Losses in
Nephrotic Syndrome

• Treatment of nephrotic syndrome
– Requires diagnosis and management of the
underlying disorder
– Medications for complications
• Diuretics, ACE inhibitors or angiotensin receptor
blockers, lipid-lowering drugs, anti-inflammatory
drugs, and immunosuppressants
– Nutrition therapy
• Helps to prevent PEM, correct lipid abnormalities,
and alleviate edema

Nephrotic Syndrome: Treatment (cont’d.)
• Protein and energy
– Adequate to meet needs: helps minimize
muscle tissue losses
– Why are high-protein diets not advised?
• Lipids
– Dietary measures usually inadequate for
controlling blood lipids
– Lipid-lowering medications may be prescribed

Nephrotic Syndrome: Treatment (cont’d.)
• Sodium and potassium
– Sodium restriction (1-2 g/day) helps control
edema (Table 22-1)
– Foods rich in potassium encouraged
• Vitamins and minerals: supplementation
– Iron and vitamin D
– Calcium (1000-1500 mg/day) may be advised

Acute Kidney Injury
• Kidney function deteriorates rapidly, over
hours or days
– Reduced urine output and build-up of
nitrogenous wastes in blood
• Causes of acute kidney injury
– Often a consequence of critical illness, sepsis,
major surgery

Acute Kidney Injury:
Causes of Acute Kidney Injury (cont’d.)
• Prerenal factors: cause a severe reduction
in blood flow to the kidneys
– Often involve a severe stressor such as heart
failure, shock, or blood loss
• Intrarenal causes: factors that damage
kidney tissue
– Infections, toxicants, drugs, or direct trauma

Acute Kidney Injury:
Causes of Acute Kidney Injury (cont’d.)
• Postrenal factors: prevent excretion of
urine due to urinary tract obstructions

Acute Kidney Injury (cont’d.)
• Consequences of acute kidney injury
– Altered composition of blood and urine
• Kidneys unable to regulate levels of electrolytes,
acid, and nitrogenous wastes in the blood
• Oliguria or anuria
– Fluid and electrolyte imbalances
• Sodium retention and edema
• Hyperkalemia: alters heart rhythm; heart failure
• Hyperphosphatemia: leads to bone calcium losses

• Consequences of acute kidney injury
– Uremia
• Nitrogen-containing compounds and various other
waste products may accumulate in the blood
• Uremic syndrome: cluster of disorders caused by
impairments in multiple body systems

• Treatment of acute kidney injury
– Combination of drug therapy, dialysis, and
nutrition therapy
• Restores fluid and electrolyte balances
• Minimizes blood concentrations of toxic waste
products
– Highly individualized
– Oliguric patients may experience diuresis
during recovery

Acute Kidney Injury: Treatment of Acute
Kidney Injury (cont’d.)
• Drug treatment for acute kidney injury
– Why may it be necessary to lower doses of
some usual medications, while others may
need to be increased?
– Nephrotoxic drugs must be avoided until
kidney function improves

• Drug treatment for acute kidney injury
– Drugs prescribed depend on cause of illness
and complications
• Immunosuppressants: inflammatory conditions
• Diuretics: edema
• Potassium-exchange resins and possibly insulin:
hyperkalemia
• Phosphate binders: high serum phosphorus
• Bicarbonate: acidosis

• Energy and protein
– Sufficient energy and protein to preserve
muscle mass, but avoid overfeeding
– Protein recommendations influenced by
kidney function, degree of catabolism, and
use of dialysis
– 20-35 kcal/kg/day with monitoring
– 0.8-1.0 g protein/kg/day (noncatabolic)
– 1.0-1.7 g/kg/day for catabolism, dialysis

• Fluids
– Estimate needs: measure urine output and
add 400-500 mL for water lost from skin,
lungs, and perspiration
• Electrolytes
– Serum electrolyte levels monitored closely
– Potassium, phosphorus, sodium restrictions
may be needed

• Enteral and parenteral nutrition
– In cases requiring additional nutritional
support, why is enteral support preferred over
parenteral nutrition?
• Box 22-3 presents an example case

Chronic Kidney Disease
• Gradual, irreversible deterioration
• Kidneys have a large functional reserve
– Chronic disease typically progresses over
many years without causing symptoms
• Most common causes
– Diabetes mellitus and hypertension
– What are other causes of chronic kidney
disease?

Chronic Kidney Disease (cont’d.)
• Consequences of chronic kidney disease
– Early stages
• Nephrons compensate by enlarging to handle the
extra workload
– End-stage renal disease
• Advanced stage in which dialysis or a kidney
transplant is needed to sustain life
– Many symptoms are nonspecific
• Delays diagnosis of the condition

Chronic Kidney Disease: Consequences
(cont’d.)
• Assessing kidney function
– Glomerular filtration rate (GFR)
• Rate at which the kidneys form filtrate
• Estimated using predictive equations based on
serum creatinine levels, age, gender, ethnicity, and
body size
• Categorized into stages (Table 22-4)
– What other tests can assess kidney function?

(cont’d.)
• Altered electrolytes and hormones
– As GFR falls, remaining nephrons increase
activity to maintain electrolyte excretion
• Electrolyte disturbances may not develop until third
or fourth stage of chronic kidney disease
– Hormonal adaptations to regulate electrolyte
levels create new complications
• Increased aldosterone ► hypertension
• Parathyroid hormone ► renal osteodystrophy

(cont’d.)
• Uremic syndrome
– Hormonal imbalances
• Lead to anemia (erythropoietin), bone disease
(active vitamin D), other problems
– Altered heart function/increased heart disease
risk
– Neuromuscular disturbances
• Malaise, irritability, sensory deficits, seizures, etc.

(cont’d.)
• Uremic syndrome
– Other effects
• Defects in platelet function and clotting factors
• Increased skin pigmentation and severe pruritus
• Suppressed immune responses

(cont’d.)
• Protein-energy malnutrition
– Anorexia: contributes to the poor food intake
• Due to hormonal disturbances, restrictive diets,
uremia, depression, other illnesses
– Nutrient losses
• Dialysis, blood draws, GI bleeding
– Negative nitrogen balance due to low-grade
inflammation

• Treatment of chronic kidney disease
– Treatment goals
• Slow disease progression
• Prevent or alleviate complications
– Drug treatment for chronic kidney disease
• Antihypertensive drugs
• Erythropoietin (epoetin) for anemia
• Others: phosphate binders, sodium bicarbonate,
and cholesterol-lowering drugs

Chronic Kidney Disease: Treatment
(cont’d.)
• Dialysis: removes excess fluid and wastes
from the blood
– Hemodialysis: blood is circulated through a
dialyzer
– Peritoneal dialysis: dialysate infused into the
peritoneal cavity, then drained
• Nutrition therapy for chronic kidney
disease (Table 22-5)

(cont’d.)
• Energy
– High-energy density foods if at risk for PEM
– Peritoneal dialysis dialysate provides kcal
• Protein: enough to meet needs and
prevent wasting
– Between 0.6 and 0.75 g/kg/day in later stages
– At least 50% from high-quality sources

(cont’d.)
• Lipids: restrict intakes of saturated fat,
trans fat, refined sugars, and alcohol
– Why are persons with chronic kidney disease
often encouraged to consume high-fat foods?
• Sodium and fluids
– Mild sodium restriction may be beneficial
– Fluids: not restricted until urine output
decreases
– What water intake restrictions apply during
dialysis?

(cont’d.)
• Potassium
– Stages 1-4: normal potassium intake levels
– Restrictions with hyperkalemia, diabetic
nephropathy, stage 5
– Potassium supplementation with potassium-
wasting diuretics
– Dialysis patients must control potassium
intakes (see Table 22-6 for a guide)

(cont’d.)
• Phosphorus, calcium, and vitamin D
– Serum phosphorus and calcium levels
monitored to minimize bone disease risk
– Elevated phosphorus levels
• Dietary restriction, sometimes phosphate binders
– What accounts for the risk of hypercalcemia?
– Vitamin D supplements

(cont’d.)
• Vitamins and minerals
– Multivitamin/mineral supplements typically
recommended
– Limit supplemental vitamin C to 70 mg/day
– Vitamin A supplements not recommended
– Hemodialysis patients: intravenous iron along
with erythropoietin therapy

(cont’d.)
• Enteral and parenteral nutrition
– Formulas: more kcalorically dense, lower
protein and electrolyte concentrations than
standard formulas
– What is intradialytic parenteral nutrition?
• Used mainly in patients with PEM who have not
responded well to oral supplements
– Dietary compliance: probably the most
challenging aspect of treatment for patients

• Kidney transplants
– Benefits
• Restores kidney function, allows a more liberal
diet, and frees the patient from routine dialysis
– What are barriers to kidney transplants?
– Immunosuppressive drug therapy
• Prevents tissue rejection following transplant
surgery
• Be aware of diet-drug interactions (Box 22-8)

Chronic Kidney Disease:
Kidney Transplants (cont’d.)
• Nutrition therapy after kidney transplant
– Most nutrients can be consumed at levels
recommended for the general population
– Primary reason for dietary adjustments: side
effects of drugs
• Serum electrolyte levels monitored
• Calcium supplementation recommended with
corticosteroids

Kidney Stones
• Kidney stone: crystalline mass that forms
within the urinary tract
• Formation of kidney stones
– Stone constituents become concentrated in
urine
• Allowing crystals to form and grow
– Most common constituent: calcium oxalate
• Less common: calcium phosphate, uric acid,
cystine, magnesium ammonium phosphate

Kidney Stones:
Formation of Kidney Stones (cont’d.)
• Factors predisposing an individual to
stone formation:
– Dehydration or low urine volume
– Changes in urine acidity
– Metabolic abnormalities
– Obstruction

Kidney Stones:
• Calcium oxalate stones
– Hypercalciuria is most common abnormality
– Hyperoxaluria also promotes formation
• Uric acid stones
– Urine is abnormally acidic, contains excessive
uric acid, or both
– Frequently associated with gout
– Diet rich in purines raises uric acid levels

Kidney Stones:
• Cystine and struvite stones
– Cystine stones form in people with inherited
disorder cystinuria
– Struvite stones
• Composed primarily of magnesium ammonium
phosphate
• Form in alkaline urine

Kidney Stones (cont’d.)
• Consequences of kidney stones
– Renal colic
• Severe, stabbing pain when stone passes through
the ureter
• Hematuria: blood in urine
– Urinary tract complications
• Urination urgency, frequent urination, or inability to
urinate
• Urinary tract obstruction, infection, acute kidney
injury

Kidney Stones (cont’d.)
• Prevention and treatment of kidney stones
– Drink 12 to 16 cups of fluids daily
• Maintain urine volumes of at least 2-2½ L per day
– Calcium oxalate stones
• Reduce urinary calcium and oxalate levels
• Adjust calcium, oxalate, protein, and sodium
intakes
• Medications: diuretics; drugs to inhibit crystal
formation; and drugs to reduce uric acid production

Kidney Stones: Prevention and
Treatment of Kidney Stones (cont’d.)
• Uric acid stones
– Diets restricted in purines may help to control
urinary uric acid levels
– Drug treatments: allopurinol to reduce uric
acid levels and potassium citrate to reduce
urine acidity

• Cystine and struvite stones
– Cystine stones:
• High fluid intakes
• Medications may be needed
– Penicillamine, tiopronin; potassium citrate
– What is a central strategy in preventing
struvite stones?

• Medical treatment for kidney stones
– Medications
• Relax ureter
• Increase urine flow
– Extracorporeal shock wave lithotripsy
• High-amplitude sound waves degrade the stone
– Surgical methods
• Higher success rate
• More invasive

Nutrition in Practice: Dialysis
• Overview of how dialysis works
• Separation of solutes from blood
• Removal of fluid from blood
• Frequency and duration of treatments
• Monitoring efficacy of dialysis
• Hemodialysis complications
• Overview of how peritoneal dialysis works

Nutrition in Practice: Dialysis
• Advantages and disadvantages of
peritoneal dialysis
• Features of continuous renal replacement
therapy

Chapter 22 Nutrition and Renal Diseases

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