Healthy kidneys
clean the blood by filtering out extra water and
wastes. They also make hormones that keep your bones
strong and blood healthy. When both of your kidneys
fail, your body holds fluid. Your blood pressure
rises. Harmful wastes build up in your body. Your
body doesn't make enough red blood cells. You
develop fatigue, nausea, and loss of appetite. When
this happens, you need treatment to replace the work
of your failed kidneys.
Your kidneys are two bean-shaped organs, each
about the size of your fist. They're located at the
back of your upper abdomen, one on either side of
your spine. The kidneys' main function is to
eliminate excess fluid and waste material from your
blood. When your kidneys lose their filtering
ability, dangerous levels of fluid and waste
accumulate in your body - a condition known as
kidney (renal) failure.
Sometimes kidney failure happens suddenly (acute
kidney failure). This is most likely to occur after
complicated surgery or a severe injury, or when
blood vessels leading to your kidneys become
blocked.
Chronic kidney failure, on the other hand,
usually develops slowly, with few signs or symptoms
in the early stages. Many people with chronic kidney
failure don't realize they have a problem until
their kidney function has decreased to less than 25
percent of normal.
High blood pressure and
diabetes
- a disorder that causes high blood sugar levels -
are the most common causes.
In end-stage renal disease, the kidneys function
at less than 10 percent of normal capacity. At this
point they simply can't sustain life. People with
end-stage renal disease need either dialysis or a
kidney transplant to stay alive. When a transplant
isn't possible - often because of poor general
health - dialysis becomes the only option.
Signs and symptoms
The signs
and symptoms of kidney failure vary, depending on whether the failure is
acute or chronic.
Acute
kidney failure
Acute kidney failure occurs when your kidneys suddenly stop filtering
waste products from your blood. The signs and symptoms may include:
Chronic kidney failure
Over time, chronic kidney failure can lead to
congestive heart failure, weak bones, stomach ulcers and damage to the
central nervous system. Unfortunately, signs and symptoms often don't
appear until irreversible damage has occurred. They include:
-
High blood
pressure
-
Unexplained
weight loss
-
Anemia
-
Nausea or
vomiting
-
Malaise or
fatigue
-
Headaches that
seem unrelated to any other cause
-
Decreased
urine output
-
Decreased
mental sharpness
-
Muscle
twitches and cramps
-
Bleeding in
the intestinal tract
-
Yellowish-brown cast to the skin
-
Persistent
itching
-
Sleep
disorders
End-stage renal disease
For some people, end-stage renal disease is the final result of chronic
kidney failure. A number of complications may develop in conjunction
with end-stage renal disease, depending on how rapidly it develops,
including:
Causes
Your kidneys are
part of a system that removes excess fluid and waste material from your
blood. Initially, blood enters your kidneys through the renal arteries,
which are branches of the aorta the main artery carrying oxygenated
blood from your heart to the rest of your body. From there, blood moves
through structures in your kidneys known as nephrons.
A single
kidney contains approximately 1 million nephrons, each consisting of a
tuft of capillary blood vessels (glomerulus) and tiny tubules that lead
into larger collecting tubes. Each tuft of capillaries filters fluid
from your bloodstream.
The
filtered material which contains both waste products and substances
vital for your health passes into the tubules. From there, waste
byproducts such as urea, uric acid and creatinine are excreted in your
urine while substances your body needs such as sugar, amino acids,
calcium and salts are absorbed back into your bloodstream. Although this
filtration system is usually able to clear all the waste products your
body produces, problems can occur if the tubules or glomeruli are
damaged or diseased.
Many
factors can damage your kidneys, including kidney diseases, injury, high
blood pressure, exposure to toxins and certain medications, kidney
stones, tumors and even infections in other parts of your body. Many of
these may cause no signs or symptoms until irreparable damage has
occurred.
high blood pressure
Multiple
myeloma
Acute
kidney failure
Factors that can cause your kidneys to shut down suddenly include:
-
Complicated
surgery, severe burns or trauma.
Many cases of acute kidney failure are related to surgery or to
trauma that involves shock or severe bleeding. In these cases, the
cause is often a drastic drop in blood pressure that prevents an
adequate amount of blood from reaching your kidneys. In addition,
when muscles are crushed in severe injuries, they release a molecule
called myoglobin that lodges in the kidney's tubules and blocks the
flow of urine.
-
Renal
ischemia.
This occurs when an obstructed or constricted blood vessel prevents
your kidneys from getting enough blood, and it may be the result of
shock or dehydration.
-
Drugs.
A number of substances can be toxic to your kidneys. These include
contrast dyes used in tests such as arteriography, which help
diagnose coronary artery disease, stroke and aneurysms. Contrast
dyes are a common cause of acute renal failure in people with
diabetic kidney disease or multiple myeloma. Certain antibiotics
especially streptomycin or gentamicin and common pain medications,
such as aspirin and ibuprofen (Advil, Motrin, others), can also
damage your kidneys. Pain medications have the potential to cause
acute kidney failure even in healthy people who use them regularly.
Antibiotics pose a greater risk of acute renal failure if you
already have liver or kidney disease, are older, or use diuretics or
other drugs that affect your kidneys.
-
Toxins.
Exposure to toxic substances including heavy metals, solvents and
excessive amounts of alcohol can lead to acute kidney failure.
-
Heatstroke.
This condition, which occurs when your body isn't able to deal with
heat stress, may lead to acute kidney failure.
-
Multiple
organ failure.
In some people, acute kidney failure occurs as part of multiple
organ failure in which the heart, lungs, liver, brain and kidneys
totally or partially shut down. This is most often the result of
major trauma or serious systemic infection (sepsis).
-
Obstructed
urine flow.
This may be due to a narrowing of the urinary tract, a tumor or
urinary stones.
-
A sudden
release of cholesterol-containing material.
This material can come from a buildup of fatty deposits in the wall
of an artery.
-
Hemolytic
uremic syndrome (HUS).
This complex condition, which results from certain strains of
Escherichia coli (E. coli) bacteria, is a leading cause of acute
kidney failure in infants and young children. HUS occurs less often
in older children and rarely strikes adults.
-
Kidney
disease (nephritis).
Diseases such as glomerulonephritis and interstitial nephritis an
inflammation of the spaces between the glomeruli and tubules can
sometimes lead to acute kidney failure.
Chronic kidney failure
Unlike acute kidney failure, chronic kidney failure slowly destroys the
nephrons in your kidneys over a period of years. Many factors may lead
to chronic kidney failure, including:
-
Diabetes.
Type 1 diabetes is a leading cause of chronic kidney failure. A small percentage of people who have had type 2
diabetes for several years also develop kidney disease. Because so
many people have type 2 diabetes, it, too, accounts for a large
number of cases of chronic renal failure.
-
High blood
pressure (hypertension).
Untreated or inadequately treated high blood pressure is another
common cause of chronic kidney failure.
-
Obstructive
nephropathy.
This occurs when urine outflow is blocked over time by an enlarged
prostate, kidney stones or tumors, or by vesicoureteral reflux, a
condition that results from urine backing up into your kidneys from
your bladder. The backflow pressure in your kidneys reduces their
function.
-
Kidney
diseases.
These include clusters of cysts in the kidneys (polycystic kidney
disease), kidney infection (pyelonephritis) and a condition that
causes your kidneys to leak protein into your urine (glomerulonephritis).
-
Renal
artery stenosis.
This is a narrowing or blockage of the renal artery before it enters
your kidney. In older adults, blockages often result when fatty
deposits accumulate under the lining of the artery walls
(atherosclerosis). Renal artery stenosis can also affect young women
who have a condition known as fibromuscular dysplasia, which causes
the walls of the arteries to become thicker. Both conditions are
often associated with high blood pressure.
-
Lead
poisoning.
Ongoing exposure to lead in lead-based paint, lead pipes,
soldering materials, jewelry and even alcohol distilled in old car
radiators can lead to chronic renal failure.
-
End-stage renal disease
Diabetes is the most common cause of end-stage renal disease. Other causes of end-stage renal disease include:
-
Vesicoureteral reflux.
This is among several causes of end-stage renal disease in children
and young adults.
-
Kidney
disease.
Polycystic kidney disease, an inherited disorder, may cause only
mild symptoms in some adults, but it can lead to end-stage renal
disease in others. Other kidney diseases that may lead to end-stage
renal disease include Bright's disease (glomerulonephritis) and
congenital nephrotic syndrome an inherited disorder that may cause
death in the first year of life.
Risk factors
Diabetes is the
single greatest risk factor for chronic renal failure. Other medical conditions that increase your risk of kidney
failure include high blood pressure (hypertension), sickle cell disease,
lupus erythematosis, atherosclerosis, chronic glomerulonephritis,
congenital nephrotic syndrome and polycystic kidney disease.
In addition, drug
overdose, excessive use of alcohol, long-term use of pain medications
such as aspirin, acetaminophen (Tylenol, others) and ibuprofen (Advil,
Motrin, others), and treatment with the antibiotics streptomycin or
gentamicin can increase your vulnerability to kidney failure. Severe
injuries or burns to your body and complicated surgery also increase
your risk.
When to seek medical advice
If you have a
chronic medical condition that puts you at increased risk of chronic
kidney failure, your doctor is likely to monitor your blood pressure and
kidney function with urine and blood tests during regularly scheduled
office visits. Call your doctor right away if you experience any of the
signs and symptoms of chronic kidney failure between visits. These may
include decreased urination, unexplained weight loss, nausea or
vomiting, fatigue, headaches or a yellowish-brown cast to your skin.
Even if you have no risk factors for kidney failure, see your doctor
immediately if you notice that you're urinating much more or much less
than usual or if you see any blood in your urine.
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