Encyclopedia of Diets - A Guide to Health and Nutrition

Heredity: Some kidney diseases result from heredi-
tary factors, and run in families.
Kidney disease interferes with the vital function of
the kidneys. The kidneys are bean-shaped organs
located near the middle of the back, just below the rib
cage. Kidneys filter blood, removing waste products
and extrawater, which become urine. They are very
efficient filtering units, processing some 200 quarts of
blood and producing about 2 quarts of urine per day in
a healthy adult. The wastes in the blood result from the
normal breakdown of active muscle and from diges-
tion. After the body extracts nutrients from ingested
food, the resulting waste is sent to the blood which is
filtered by the kidneys. The kidneys also release three
important hormones:

Erythropoietin, which stimulates the bones to make
red blood cells.

Renin, which regulates blood pressure.

The active form of vitamin D, required to regulate

calcium for bones and for normal chemical balance

in the body.

Damaged kidneys do not clean the blood effi-

ciently. Instead, waste products and fluid build up in

the blood leading to kidney disease that often cannot

be cured. In the early stages of a kidney disease, treat-

ment may be able to make the kidneys last longer.

Eventually, kidneys may stop working altogether (kid-

ney failure), and the body fills with extra water and

waste products (uremia), which may lead to seizures or

coma, and ultimately to death. When kidneys stop work-

ing completely, dialysis or a kidney transplantation is

required.

Dialysis is an artificial way to filter blood after the

kidneys have failed. With hemodialysis, the blood

travels through tubes to a dialyzer, a machine that

removes wastes and extra fluid. The cleaned blood is

then returned to the body. The procedure is usually

performed at a dialysis center three times per week for

3–4 hours. In peritoneal dialysis, a fluid (dialysate) is

dripped into the abdomen to capture the waste prod-

ucts from the blood. After a few hours, the dialysate is

drained out, and a fresh bag of dialysate is dripped into

the abdomen. Patients can perform peritoneal dialysis

themselves.

Description

Renal nutrition is concerned with ensuring that

kidney patients eat the right foods to make dialysis

efficient and improve health. Dialysis clinics have die-

titians on staff who help patients plan meals. Standard

guidelines are: eating more highproteinfoods, and

less high salt, high potassium, and high phosphorus

foods. Patients are also advised on safe fluid intake

levels. The National Kidney Foundation offers the fol-

lowing dietary advice to adults starting hemodialysis:

Sodium and salt

Use less salt and eat fewer salty foods to help to

control blood pressure and reduce weight gains

between dialysis sessions.

Use herbs, spices, and low–salt flavor enhancers

instead of salt.

Avoid salt substitutes made with potassium.

Protein and meat

People on dialysis need to eat more protein. Eat a

high-protein food (meat, fish, poultry, fresh pork, or

eggs at every meal, for a total of 8–10 ounces of high

protein foods everyday.

SOURCE: National Institute of Diabetes and Digestive and Kidney

Diseases, National Institutes of Health, U.S. Department of

Health and Human Services

Conditions related to kidney failure and treatments

Anemia and Erythropoietin (EPO)—Anemia is common in people with

kidney disease because the kidneys produce the hormone erythropoietin,

or EPO, which stimulates the bone marrow to produce red blood cells.

Diseased kidneys often don’t make enough EPO, causing the bone marrow

to make fewer red blood cells. EPO is available commercially and is

commonly given to patients on dialysis. Anemia can also contribute to

heart problems.

Renal Osteodystrophy—This bone disease of kidney failure affects 90% of

dialysis patients. The condition causes bones to become thin and weak or

to form incorrectly and affects both children and adults. Symptoms can be

seen in growing children with kidney disease even before they start

dialysis. Older patients and women who have gone through menopause

are at greater risk for this disease.

Itching (Pruritus)—Many patients treated with hemodialysis complain of

itchy skin, which is often worse during or just after treatment. Itching can

worsen from wastes in the bloodstream that current dialyzer membranes

can’t remove from the blood. The problem can also be related to high levels

of parathyroid hormone (PTH), which help control the levels of calcium

and phosphorus in the blood.

Sleep disorders—Patients on dialysis often have insomnia, which can be

caused by aching, uncomfortable, jittery, or “restless” legs (a condition

related to nerve damage or chemical imbalances). Some patients may have

sleep apnea syndrome, signaled by snoring and breaks in snoring. Sleep

apnea may be related to the effects of advanced kidney failure on the

control of breathing. Overtime, sleep disturbances can lead to “day-night

reversal” (insomnia at night, sleepiness during the day), headache,

depression, and decreased alertness.

Dialysis-related Amyloidosis (DRA)—It is common for patients who have

been on dialysis for more than 5 years to develop DRA. It is the result of

proteins in the blood depositing on joints and tendons, causing pain,

stiffness, and fluid in the joints, as is the case with arthritis. Working

kidneys filter out these proteins, but dialysis filters are not as effective.

(Illustration by GGS Information Services/Thomson Gale.)

Renal nutrition