Download Kidney Stones

NUTRITION in KIDNEY
DISORDER (CKD)
RENAL PHYSIOLOGY
The kidneys keep the body’s fluids,
electrolytes, and organic solutes in a
healthy balance or homeostasis.
Their functional units are the millions of
nephrons in the renal cortex which filter
most constituents of the blood other than
red blood cells and protein, reabsorb
needed substances, secrete hydrogen
ions to maintain acid-base balance,
maintains blood pressure and secrete
wastes.
Urine formation consists of four basic
processes:
1. glomerular filtration
2. tubular reabsorption
3. tubular secretion and
4. urine concentration.
Several disease conditions can interfere with
these functions.
Inflammatory and degenerative diseases
can involve the small blood vessels and
membranes in the nephrons.
Urinary tract infections and kidney
stones can interfere with normal drainage,
causing further infection and tissue
damage.
Circulatory disorders, such as
hypertension, can damage the small renal
arteries.
Other diseases, such as diabetes, gout, and
urinary tract abnormalities can lead to
impaired function, infection, or obstruction.
Toxic agents such as insecticides,
solvents, and certain drugs may also harm
renal tissue.
Nephrotic Syndrome
In nephrotic syndrome, an injury to the
glomerular basement membrane causes
an increased glomerular permeability,
resulting in the loss of albumin and other
plasma proteins in the urine.
Urinary protein losses greater than 3-3.5
grams per day usually indicate nephrotic
syndrome.
The loss of albumin leads to edema.
Low albumin levels also trigger cholesterol
and lipoprotein synthesis in the liver,
resulting in hyperlipidemia.
Q: Will you advice an increase in protein
intake in these patients?
Protein:
High-protein diets are not recommended as
they may encourage damage to the
nephrons, leading to a progression of
renal insufficiency.
Since albumin losses in nephrotic patients
are due to increased catabolism, rather
than a reduction in protein synthesis, lowprotein diets, which decrease catabolism,
may be more beneficial.
Acute Renal Failure
Acute renal failure, manifested by oliguria
or anuria, usually occurs suddenly and is
often reversible. It is marked by a
reduction in the glomerular filtration rate
and a modification in the kidneys ability to
excrete metabolic wastes.
Its causes can be prerenal, intrinsic, and
postrenal.
– Prerenal causes include severe
dehydration and circulatory collapse.
– Causes intrinsic to the kidney include
acute tubular necrosis, nephrotoxicity,
vascular disorders, and acute
glomerulonephritis.
– Obstructive (postrenal) causes include
benign prostatic hypertrophy and
bladder or prostate cancer.
Diet in Acute Renal Failure
Protein: A low-protein diet (0.5-0.6 grams
per kilogram) is recommended initially.
Protein may be increased in the diet as
the glomerular filtration rate increases to
normal.
• If dialysis is initiated, the protein level
may be increased to 1.0-1.5 grams per
kilogram per day if necessary to
compensate for protein losses in the
dialysate.
Diet in Acute Renal Failure
Calories: Calorie needs are generally
elevated (35-50 kilocalories per kilogram)
in order to provide positive nitrogen
balance under stressful conditions. As
protein is usually quite restricted, calorie
needs may be met by providing greater
amounts of carbohydrate and fat in the
diet.
Sodium and Fluid: Sodium is restricted
depending on urinary excretion, edema,
serum sodium levels, and dialysis needs.
• During the oliguric phase, sodium may be
restricted to 500-1000 milligrams per day,
and fluid requirements are based on
replacing losses via urine, vomitus, and
diarrhea, plus approximately 500 milliliters
per day.
Potassium: Potassium requirements vary
depending on hemodynamic status and
the degree of hypermetabolism due to
stress, infection, or fever.
• High potassium levels are treated by
dialysis or with kayexalate, an exchange
resin which substitutes sodium for
potassium in the gastrointestinal tract.
• During the oliguric phase, potassium may
be restricted to 1,000 milligrams per day.
Chronic Renal Failure
• Approximately 90 percent of cases of endstage renal disease are attributable to
diabetes mellitus, glomerulonephritis, or
hypertension.
• Kidney failure results in fluid and
electrolyte imbalances, the build up of
nitrogenous wastes, and reduced ability to
produce renal hormones.
• The two treatment options are transplantation or dialysis.
• Mild renal insufficiency is defined as 40-80
percent of renal function.
• Moderate insufficiency is defined as 15-40
percent, and
• severe renal insufficiency is below these
figures.
Diet in Chronic Renal Failure
• Low-protein diets may slow the
progression of mild and moderate renal
insufficiency.
• Therapeutic diets using plant sources of
protein are more effective in delaying the
progression of renal insufficiency,
compared to those using animal proteins.
• Vegan (pure vegetarian) diets have been
shown to provide adequate protein.
Dialysis Patients
• Dialysis changes dietary needs. Patients
undergoing typical hemodialysis, involving
about three treatments per week, follow
diets that are restricted in protein, sodium,
potassium, phosphorus, and fluid.
• Patients on continuous ambulatory
peritoneal dialysis, involving several
dialysate exchanges per day, can be more
liberal in protein, sodium, potassium, and
fluid intake.
Sodium: Sodium intake must be modified to
prevent hypertension, congestive heart
failure, and pulmonary edema. Limiting
intake will help avoid thirst and maintain
acceptable fluid balance.
Fluid: Fluid consumption should be
controlled to avoid congestive heart
failure, pulmonary edema, hypertension,
and swelling of the legs and feet. Fluid
allowances are 1,000-1,5000 milliliters per
day and are based on urine output and
type of dialysis.
Protein: Protein requirements range from
1.1-1.5 grams per kilogram, depending on
the type of dialysis used and the patient’s
nutritional status. It is important to ensure
sufficient protein to maintain visceral
protein stores, but to avoid excesses that
could lead the accumulation of
nitrogenous waste products in the blood
(uremia).
Phosphorus: Kidney failure causes high
levels of phosphorus to build up in the
blood and disrupts calcium/phosphorus
balance.
• Elevated phosphorus levels can lead to
metastatic calcification (soft tissue
calcification), secondary hyperparathyroidism, and renal osteodystrophy.
Renal osteodystrophy.
• Diseases of bone in which there is failure
of normal development or abnormal
metabolism in bone which is already
mature.
• Principal clinical signs are distortion and
enlargement of bones, susceptibility to
fracture, and abnormalities of gait and
posture
Potassium: Potassium restrictions depend
on serum potassium levels, the type of
dialysis, medications, and residual renal
function. Patients on hemodialysis are
usually restricted to 2,000-3,000
milligrams per day to prevent
hyperkalemia between treatments.
• Patients on peritoneal dialysis may follow
a more liberal dietary potassium intake, as
potassium is lost in the dialysate solution
during daily exchanges.
Kidney Stones
• About 12 percent of Americans develop a
kidney stone at some point in their lives.
Stones usually result from the
crystallization of calcium (which originally
came in foods or supplements) and
oxalate, a part of many plant foods.
• Some people have a tendency to lose
excessive amounts of calcium or oxalate
through their kidneys, and they have a
greater likelihood of a stone.
• Kidney stones can also form from uric
acid, which is a breakdown product of
protein, or from struvite (ammoniomagnesium phosphate) or cystine.
• Nutritional steps are important in
preventing stones and can also help
prevent recurrences, which is important
given that 30-50 percent of people
diagnosed with a renal stone have a
recurrence within five years.
• Preventing stones is like keeping a salt
crystal from forming in a glass of salty
water.
• You can either reduce the concentration of
salt or add more water.
• Epidemiologic studies have shown that
certain parts of the diet help reduce the
amount of calcium that filters into the
urine.
• It is a simple matter to put these factors to
work clinically.
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WHAT’S IN A STONE?
Calcium oxalate 72%
Uric acid
23%
Ammoniomagnesium phosphate
(struvite) 5%
Cystine
<1%
• The prevalence of kidney stones is three
times higher in men than women, and is
higher among Caucasians than Asians or
African Americans, for reasons that are not
clear.
• They are especially likely to strike between
the ages of 40 and 60.
Protective Foods
Water.
• Water dilutes the urine and keeps calcium,
oxalates, and uric acid in solution. In
research studies, those subjects whose
total fluid intake (from all sources) over 24
hours was roughly 2.5 liters, the risk of a
stone was about one-third less than that of
subjects drinking only half that much.
• (They do not need to drink 2.5 liters of
water per day; rather this is the total fluid
consumption, including juices, soups, etc.)
High-Potassium Foods.
A study of 46,000 men conducted by
Harvard University researchers found that
a high potassium intake can cut the risk of
kidney stones in half.
• Potassium helps the kidneys retain
calcium, rather than sending it out into the
urine.
• Potassium supplements are not generally
necessary. Rather, a diet including regular
servings of fruits, vegetables, and beans
supplies plenty of potassium.
Calcium. Although most stones contain
calcium, the calcium in foods does not
necessarily contribute to stones.
• Calcium supplements taken between
meals may increase the risk of stones,
because about 8 percent of any extra
dietary calcium passes into the urine.
• On the other hand, calcium consumed with
meals has the opposite effect, reducing
the risk of stones.
• The reason, apparently, is that calcium
binds to oxalates in foods and holds them
in the digestive tract, rather than allowing
them to be absorbed.
Caffeine. Caffeinated beverages reduce the
risk of stones. Caffeine’s diuretic effect
causes the loss of both water and calcium,
but the water loss is apparently the
predominant effect. Similarly, alcoholic
beverages are associated with a reduced
risk of kidney stones, again presumably
due to a diuretic effect. This is not a
compelling reason to drink either coffee or
alcohol, but their diuretic actions do
present this advantage.
Problem Foods
Animal Protein.
Animal proteins cause calcium to be
leached from the bones and excreted in
the urine where it can form stones. Diets
rich in animal proteins also increase uric
acid excretion.
A modest increase in animal protein
intake, from less than 50 grams to 77
grams per day, was associated with a 33
percent increased risk of stone formation.
• Between 1958 and the late 1960s, there
was a sharp increase in the incidence of
kidney stones in Great Britain.
• During that period, there was no
substantial change in the amount of
calcium or oxalate-containing foods
consumed. However, the consumption of
vegetables decreased, and the use of
poultry, fish, and red meat increased.
Statistical analyses showed a strong
relationship between the incidence of
stones and animal protein consumption.
Sodium. Sodium increases the passage of
calcium through the kidney and increases
the risk of stones. When people cut their
salt (sodium chloride) intake in half, they
reduce their daily need for calcium by
about 160 milligrams.
• Plants of any kind—grains, vegetables,
legumes, and fruits—contain almost no
sodium at all unless it is added during
canning or other processing.
• Dairy products and meats contain more
salt than plant products, and table salt,
frozen meals, and canned and snack
foods are the highest-sodium food
products.
Sugar.
Sugar accelerates calcium losses through
the kidney. In the Nurses’ Health Study,
those who consumed, on average, 60
grams or more of sugar (sucrose) per day
had a 50 percent higher risk of stones than
those who consumed only about 20
grams.
Climate. Kidney stones are also more
common in warm climates, presumably
because perspiration leads to dehydration
and a more concentrated urine, and
because sunlight increases the production
of vitamin D in the skin which, in turn,
increases calcium absorption from the
digestive tract.
• Surprisingly, oxalate-rich foods, such as
chocolate, nuts, tea, and spinach, are not
associated with a higher risk of renal
stones,
Helping Patients Avoid Kidney Stones
• Encourage patients to drink plenty of water
or other fluids, staying ahead of their thirst.
• Diets including generous amounts of
vegetables, fruits, and beans are rich in
potassium and very low in sodium.
Helping Patients Avoid Kidney Stones,
cont’n
• If you prescribe calcium supplements,
encourage patients to take them with meals,
rather than between meals.
• Encourage patients to avoid animal products.
Their proteins and sodium content increase
the risk of stones.
• Patients should keep salt and sugar use
modest.
What foods are high in protein?
• meat (beef, chicken, pork, turkey)
• fish
• seafood (shrimp, scallops, clams, oysters)
• eggs
• dairy products (milk, cheese, ice cream,
yogurt, pudding)
What foods are high in potassium?
Most foods contain some amount of potassium.
bananas
prunes
oranges
potatoes
orange juice
sweet potatoes
grapefruit juice
tomato sauce
cantaloupe
What foods are high in phosphorus?
• The following foods are high in
phosphorous and should be restricted.
• Dairy products, including:
– milk (all kinds: whole, low-fat, skim,
chocolate, and buttermilk)
– cheeses (all except cream cheese)
– puddings and custards
– yogurt
– ice cream
Foods high in sodium:
• canned foods (vegetables, meats, pasta
meals)
• processed foods (meats such as bologna,
pepperoni, salami, hot dogs, sausage)
• cheese
• dried pasta and rice mixes
• soups (canned and dried)
• snack foods (chips, popcorn, pretzels,
cheese puffs, salted nuts, etc.)
• dips, sauces, and salad dressings
• meats, chicken, turkey, and fish (especially
organ meats)
• dried beans and peas, including:
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–
–
–
–
black-eyes
field peas
kidney
navy
northern
pinto
lima
• nuts (all kinds and peanut butter)
• seeds, bran, and whole grain cereals and
breads
DONE!!