The Prostate Gland
The prostate is a walnut-sized gland that forms part of
the male
reproductive system. The gland is made of two lobes, or regions,
enclosed by an outer layer of tissue. As the diagrams show, the
prostate is located in front of the rectum and just below the bladder,
where urine is stored. The prostate also surrounds the urethra, the
canal through which urine passes out of the body.
Scientists do not know all the prostate's functions. One
of its main
roles, though, is to squeeze fluid into the urethra as sperm move
through during sexual climax. This fluid, which helps make up semen,
energizes the sperm and makes the vaginal canal less acidic.
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Benign Prostatic Hyperplasia: A Common Part of Aging
It is common for the prostate gland to become enlarged
as a man
ages. Doctors call this condition benign prostatic hyperplasia (BPH),
or benign prostatic hypertrophy.
Normal
urine flow.
Urine
flow with BPH.
As a man matures, the prostate goes through two main
periods of
growth. The first occurs early in puberty, when the prostate doubles in
size. At around age 25, the gland begins to grow again. This second
growth phase often results, years later, in BPH.
Though the prostate continues to grow during most of a
man's life,
the enlargement doesn't usually cause problems until late in life. BPH
rarely causes symptoms before age 40, but more than half of men in
their sixties and as many as 90 percent in their seventies and eighties
have some symptoms of BPH.
As the prostate enlarges, the layer of tissue
surrounding it stops
it from expanding, causing the gland to press against the urethra like
a clamp on a garden hose. The bladder wall becomes thicker and
irritable. The bladder begins to contract even when it contains small
amounts of urine, causing more frequent urination. Eventually, the
bladder weakens and loses the ability to empty itself, so some of the
urine remains in the bladder. The narrowing of the urethra and partial
emptying of the bladder cause many of the problems associated with BPH.
Many people feel uncomfortable talking about the
prostate, since the
gland plays a role in both sex and urination. Still, prostate
enlargement is as common a part of aging as gray hair. As life
expectancy rises, so does the occurrence of BPH. In the United States
in 2000, there were 4.5 million visits to physicians for BPH.
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Why BPH Occurs
The cause of BPH is not well understood. No definite
information on
risk factors exists. For centuries, it has been known that BPH occurs
mainly in older men and that it doesn't develop in men whose testes
were removed before puberty. For this reason, some researchers believe
that factors related to aging and the testes may spur the development
of BPH.
Throughout their lives, men produce both testosterone,
an important
male hormone, and small amounts of estrogen, a female hormone. As men
age, the amount of active testosterone in the blood decreases, leaving
a higher proportion of estrogen. Studies done on animals have suggested
that BPH may occur because the higher amount of estrogen within the
gland increases the activity of substances that promote cell growth.
Another theory focuses on dihydrotestosterone (DHT), a
substance
derived from testosterone in the prostate, which may help control its
growth. Most animals lose their ability to produce DHT as they age.
However, some research has indicated that even with a drop in the
blood's testosterone level, older men continue to produce and
accumulate high levels of DHT in the prostate. This accumulation of DHT
may encourage the growth of cells. Scientists have also noted that men
who do not produce DHT do not develop BPH.
Some researchers suggest that BPH may develop as a
result of
"instructions" given to cells early in life. According to this theory,
BPH occurs because cells in one section of the gland follow these
instructions and "reawaken" later in life. These "reawakened" cells
then deliver signals to other cells in the gland, instructing them to
grow or making them more sensitive to hormones that influence growth.
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Symptoms
Many symptoms of BPH stem from obstruction of the
urethra and
gradual loss of bladder function, which results in incomplete emptying
of the bladder. The symptoms of BPH vary, but the most common ones
involve changes or problems with urination, such as
- a hesitant, interrupted, weak stream
- urgency and leaking or dribbling
- more frequent urination, especially at night
The size of the prostate does not always determine how
severe the
obstruction or the symptoms will be. Some men with greatly enlarged
glands have little obstruction and few symptoms while others, whose
glands are less enlarged, have more blockage and greater problems.
Sometimes a man may not know he has any obstruction
until he
suddenly finds himself unable to urinate at all. This condition, called
acute urinary retention, may be triggered by taking over-the-counter
cold or allergy medicines. Such medicines contain a decongestant drug,
known as a sympathomimetic. A potential side effect of this drug may
prevent the bladder opening from relaxing and allowing urine to empty.
When partial obstruction is present, urinary retention also can be
brought on by alcohol, cold temperatures, or a long period of
immobility.
It is important to tell your doctor about urinary
problems such as
those described above. In eight out of 10 cases, these symptoms suggest
BPH, but they also can signal other, more serious conditions that
require prompt treatment. These conditions, including prostate cancer,
can be ruled out only by a doctor's examination.
Severe BPH can cause serious problems over time. Urine
retention and
strain on the bladder can lead to urinary tract infections, bladder or
kidney damage, bladder stones, and incontinence—the inability
to
control urination. If the bladder is permanently damaged, treatment for
BPH may be ineffective. When BPH is found in its earlier stages, there
is a lower risk of developing such complications.
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Diagnosis
You may first notice symptoms of BPH yourself, or your
doctor may
find that your prostate is enlarged during a routine checkup. When BPH
is suspected, you may be referred to a urologist, a doctor who
specializes in problems of the urinary tract and the male reproductive
system. Several tests help the doctor identify the problem and decide
whether surgery is needed. The tests vary from patient to patient, but
the following are the most common.
Digital Rectal Examination (DRE)
This examination is usually the first test done. The
doctor inserts
a gloved finger into the rectum and feels the part of the prostate next
to the rectum. This examination gives the doctor a general idea of the
size and condition of the gland.
Prostate-Specific Antigen (PSA) Blood Test
To rule out cancer as a cause of urinary symptoms, your
doctor may
recommend a PSA blood test. PSA, a protein produced by prostate cells,
is frequently present at elevated levels in the blood of men who have
prostate cancer. The U.S. Food and Drug Administration (FDA) has
approved a PSA test for use in conjunction with a digital rectal
examination to help detect prostate cancer in men who are age 50 or
older and for monitoring men with prostate cancer after treatment.
However, much remains unknown about the interpretation of PSA levels,
the test's ability to discriminate cancer from benign prostate
conditions, and the best course of action following a finding of
elevated PSA.
A fact sheet titled "The Prostate-Specific Antigen (PSA)
Test:
Questions and Answers " can be found on the National Cancer Institute
website at www.cancer.gov/cancertopics/factsheet/Detection/PSA.
Rectal Ultrasound and Prostate Biopsy
If there is a suspicion of prostate cancer, your doctor
may
recommend a test with rectal ultrasound. In this procedure, a probe
inserted in the rectum directs sound waves at the prostate. The echo
patterns of the sound waves form an image of the prostate gland on a
display screen. To determine whether an abnormal-looking area is indeed
a tumor, the doctor can use the probe and the ultrasound images to
guide a biopsy needle to the suspected tumor. The needle collects a few
pieces of prostate tissue for examination with a microscope.
Urine Flow Study
Your doctor may ask you to urinate into a special device
that
measures how quickly the urine is flowing. A reduced flow often
suggests BPH.
Cystoscopy
In this examination, the doctor inserts a small tube
through the
opening of the urethra in the penis. This procedure is done after a
solution numbs the inside of the penis so all sensation is lost. The
tube, called a cystoscope, contains a lens and a light system that help
the doctor see the inside of the urethra and the bladder. This test
allows the doctor to determine the size of the gland and identify the
location and degree of the obstruction.
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Treatment
Men who have BPH with symptoms usually need some kind of
treatment
at some time. However, a number of researchers have questioned the need
for early treatment when the gland is just mildly enlarged. The results
of their studies indicate that early treatment may not be needed
because the symptoms of BPH clear up without treatment in as many as
one-third of all mild cases. Instead of immediate treatment, they
suggest regular checkups to watch for early problems. If the condition
begins to pose a danger to the patient's health or causes a major
inconvenience to him, treatment is usually recommended.
Since BPH can cause urinary tract infections, a doctor
will usually
clear up any infection with antibiotics before treating the BPH itself.
Although the need for treatment is not usually urgent, doctors
generally advise going ahead with treatment once the problems become
bothersome or present a health risk.
The following section describes the types of treatment
that are most commonly used for BPH.
Drug Treatment
Over the years, researchers have tried to find a way to
shrink or at
least stop the growth of the prostate without using surgery. The FDA
has approved six drugs to relieve common symptoms associated with an
enlarged prostate.
Finasteride (Proscar), FDA-approved in 1992, and
dutasteride
(Avodart), FDA-approved in 2001, inhibit production of the hormone DHT,
which is involved with prostate enlargement. The use of either of these
drugs can either prevent progression of growth of the prostate or
actually shrink the prostate in some men.
The FDA also approved the drugs terazosin (Hytrin) in
1993,
doxazosin (Cardura) in 1995, tamsulosin (Flomax) in 1997, and alfuzosin
(Uroxatral) in 2003 for the treatment of BPH. All four drugs act by
relaxing the smooth muscle of the prostate and bladder neck to improve
urine flow and to reduce bladder outlet obstruction. The four drugs
belong to the class known as alpha blockers. Terazosin and doxazosin
were developed first to treat high blood pressure. Tamsulosin and
alfuzosin were developed specifically to treat BPH.
The Medical Therapy of Prostatic Symptoms (MTOPS) Trial,
supported
by the National Institute of Diabetes and Digestive and Kidney Diseases
(NIDDK), recently found that using finasteride and doxazosin together
is more effective than using either drug alone to relieve symptoms and
prevent BPH progression. The two-drug regimen reduced the risk of BPH
progression by 67 percent, compared with 39 percent for doxazosin alone
and 34 percent for finasteride alone.
Minimally Invasive Therapy
Because drug treatment is not effective in all cases,
researchers in
recent years have developed a number of procedures that relieve BPH
symptoms but are less invasive than conventional surgery.
Transurethral microwave procedures.
In 1996, the
FDA approved a device that uses microwaves to heat and destroy excess
prostate tissue. In the procedure called transurethral microwave
thermotherapy (TUMT), the device sends computer-regulated microwaves
through a catheter to heat selected portions of the prostate to at
least 111 degrees Fahrenheit. A cooling system protects the urinary
tract during the procedure.
The procedure takes about 1 hour and can be performed on
an
outpatient basis without general anesthesia. TUMT has not been reported
to lead to erectile dysfunction or incontinence.
Although microwave therapy does not cure BPH, it reduces
urinary
frequency, urgency, straining, and intermittent flow. It does not
correct the problem of incomplete emptying of the bladder. Ongoing
research will determine any long-term effects of microwave therapy and
who might benefit most from this therapy.
Transurethral needle ablation.
Also in 1996, the FDA approved the minimally invasive transurethral
needle ablation (TUNA) system for the treatment of BPH.
The TUNA system delivers low-level radiofrequency energy
through
twin needles to burn away a well-defined region of the enlarged
prostate. Shields protect the urethra from heat damage. The TUNA system
improves urine flow and relieves symptoms with fewer side effects when
compared with transurethral resection of the prostate (TURP). No
incontinence or impotence has been observed.
Water-induced thermotherapy.
This therapy uses
heated water to destroy excess tissue in the prostate. A catheter
containing multiple shafts is positioned in the urethra so that a
treatment balloon rests in the middle of the prostate. A computer
controls the temperature of the water, which flows into the balloon and
heats the surrounding prostate tissue. The system focuses the heat in a
precise region of the prostate. Surrounding tissues in the urethra and
bladder are protected. Destroyed tissue either escapes with urine
through the urethra or is reabsorbed by the body.
High-intensity focused ultrasound.
The use of
ultrasound waves to destroy prostate tissue is still undergoing
clinical trials in the United States. The FDA has not yet approved
high-intensity focused ultrasound.
Surgical Treatment
Most doctors recommend removal of the enlarged part of
the prostate
as the best long-term solution for patients with BPH. With surgery for
BPH, only the enlarged tissue that is pressing against the urethra is
removed; the rest of the inside tissue and the outside capsule are left
intact. Surgery usually relieves the obstruction and incomplete
emptying caused by BPH. The following section describes the types of
surgery that are used.
Transurethral surgery. In
this type of surgery, no
external incision is needed. After giving anesthesia, the surgeon
reaches the prostate by inserting an instrument through the urethra.
A procedure called transurethral resection of the
prostate (TURP) is
used for 90 percent of all prostate surgeries done for BPH. With TURP,
an instrument called a resectoscope is inserted through the penis. The
resectoscope, which is about 12 inches long and 1/2 inch in diameter,
contains a light, valves for controlling irrigating fluid, and an
electrical loop that cuts tissue and seals blood vessels.
During the 90-minute operation, the surgeon uses the
resectoscope's
wire loop to remove the obstructing tissue one piece at a time. The
pieces of tissue are carried by the fluid into the bladder and then
flushed out at the end of the operation.
Most doctors suggest using TURP whenever possible.
Transurethral
procedures are less traumatic than open forms of surgery and require a
shorter recovery period. One possible side effect of TURP is
retrograde, or backward, ejaculation. In this condition, semen flows
backward into the bladder during climax instead of out the urethra.
Another surgical procedure is called transurethral
incision of the
prostate (TUIP). Instead of removing tissue, as with TURP, this
procedure widens the urethra by making a few small cuts in the bladder
neck, where the urethra joins the bladder, and in the prostate gland
itself. Although some people believe that TUIP gives the same relief as
TURP with less risk of side effects such as retrograde ejaculation, its
advantages and long-term side effects have not been clearly established.
Open surgery. In the few
cases when a transurethral
procedure cannot be used, open surgery, which requires an external
incision, may be used. Open surgery is often done when the gland is
greatly enlarged, when there are complicating factors, or when the
bladder has been damaged and needs to be repaired. The location of the
enlargement within the gland and the patient's general health help the
surgeon decide which of the three open procedures to use.
With all the open procedures, anesthesia is given and an
incision is
made. Once the surgeon reaches the prostate capsule, he or she scoops
out the enlarged tissue from inside the gland.
Laser surgery. In March
1996, the FDA approved a
surgical procedure that employs side-firing laser fibers and Nd: YAG
lasers to vaporize obstructing prostate tissue. The doctor passes the
laser fiber through the urethra into the prostate using a cystoscope
and then delivers several bursts of energy lasting 30 to 60 seconds.
The laser energy destroys prostate tissue and causes shrinkage. As with
TURP, laser surgery requires anesthesia and a hospital stay. One
advantage of laser surgery over TURP is that laser surgery causes
little blood loss. Laser surgery also allows for a quicker recovery
time. But laser surgery may not be effective on larger prostates. The
long-term effectiveness of laser surgery is not known.
Newer procedures that use laser technology can be
performed on an outpatient basis.
Photoselective vaporization of the
prostate (PVP). PVP uses a high-energy laser to destroy
prostate tissue and seal the treated area.
Interstitial laser coagulation.
Unlike other laser
procedures, interstitial laser coagulation places the tip of the
fiberoptic probe directly into the prostate tissue to destroy it.
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Your Recovery After Surgery in the Hospital
The amount of time you will stay in the hospital depends
on the type of surgery you had and how quickly you recover.
Foley catheter
At the end of surgery, a special catheter is inserted
through the
opening of the penis to drain urine from the bladder into a collection
bag. Called a Foley catheter, this device has a water-filled balloon on
the end that is put in the bladder, which keeps it in place.
This catheter is usually left in place for several days.
Sometimes,
the catheter causes recurring painful bladder spasms the day after
surgery. These spasms may be difficult to control, but they will
eventually disappear.
You may also be given antibiotics while you are in the
hospital.
Many doctors start giving this medicine before or soon after surgery to
prevent infection. However, some recent studies suggest that
antibiotics may not be needed in every case, and your doctor may prefer
to wait until an infection is present to give them.
After surgery, you will probably notice some blood or
clots in your
urine as the wound starts to heal. If your bladder is being irrigated
(flushed with water), you may notice that your urine becomes red once
the irrigation is stopped. Some bleeding is normal, and it should clear
up by the time you leave the hospital. During your recovery, it is
important to drink a lot of water (up to 8 cups a day) to help flush
out the bladder and speed healing.
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Do's and Don'ts
Take it easy the first few weeks after you get home. You
may not
have any pain, but you still have an incision that is
healing—even with
transurethral surgery, where the incision can't be seen. Since many
people try to do too much at the beginning and then have a setback, it
is a good idea to talk with your doctor before resuming your normal
routine. During this initial period of recovery at home, avoid any
straining or sudden movements that could tear the incision. Here are
some guidelines:
- Continue drinking a lot of water to flush the bladder.
- Avoid straining when having a bowel movement.
- Eat a balanced diet to prevent constipation. If
constipation occurs, ask your doctor if you can take a laxative.
- Don't do any heavy lifting.
- Don't drive or operate machinery.
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Getting Back to Normal After Surgery
Even though you should feel much better by the time you
leave the
hospital, it will probably take a couple of months for you to heal
completely. During the recovery period, the following are some common
problems that can occur.
Problems Urinating
You may notice that your urinary stream is stronger
right after
surgery, but it may take awhile before you can urinate completely
normally again. After the catheter is removed, urine will pass over the
surgical wound on the prostate, and you may initially have some
discomfort or feel a sense of urgency when you urinate. This problem
will gradually lessen, and after a couple of months you should be able
to urinate less frequently and more easily.
Incontinence
As the bladder returns to normal, you may have some
temporary
problems controlling urination, but long-term incontinence rarely
occurs. Doctors find that the longer problems existed before surgery,
the longer it takes for the bladder to regain its full function after
the operation.
Bleeding
In the first few weeks after transurethral surgery, the
scab inside
the bladder may loosen, and blood may suddenly appear in the urine.
Although this can be alarming, the bleeding usually stops with a short
period of resting in bed and drinking fluids. However, if your urine is
so red that it is difficult to see through or if it contains clots or
if you feel any discomfort, be sure to contact your doctor.
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Sexual Function After Surgery
Many men worry about whether surgery for BPH will affect
their
ability to enjoy sex. Some sources state that sexual function is rarely
affected, while others claim that it can cause problems in up to 30
percent of cases. However, most doctors say that even though it takes
awhile for sexual function to return fully, with time, most men are
able to enjoy sex again.
Complete recovery of sexual function may take up to 1
year, lagging
behind a person's general recovery. The exact length of time depends on
how long after symptoms appeared that BPH surgery was done and on the
type of surgery. Following is a summary of how surgery is likely to
affect the following aspects of sexual function.
Erections
Most doctors agree that if you were able to maintain an
erection
shortly before surgery, you will probably be able to have erections
afterward. Surgery rarely causes a loss of erectile function. However,
surgery cannot usually restore function that was lost before the
operation.
Ejaculation
Although most men are able to continue having erections
after
surgery, a prostate procedure frequently makes them sterile (unable to
father children) by causing a condition called retrograde ejaculation
or dry climax.
During sexual activity, sperm from the testes enters the
urethra
near the opening of the bladder. Normally, a muscle blocks off the
entrance to the bladder, and the semen is expelled through the penis.
However, the coring action of prostate surgery cuts this muscle as it
widens the neck of the bladder. Following surgery, the semen takes the
path of least resistance and enters the wider opening to the bladder
rather than being expelled through the penis. Later it is harmlessly
flushed out with urine. In some cases, this condition can be treated
with a drug called pseudoephedrine, found in many cold medicines, or
imipramine. These drugs improve muscle tone at the bladder neck and
keep semen from entering the bladder.
Orgasm
Most men find little or no difference in the sensation
of orgasm, or
sexual climax, before and after surgery. Although it may take some time
to get used to retrograde ejaculation, you should eventually find sex
as pleasurable after surgery as before.
Many people have found that concerns about sexual
function can
interfere with sex as much as the operation itself. Understanding the
surgical procedure and talking over any worries with the doctor before
surgery often help men regain sexual function earlier. Many men also
find it helpful to talk with a counselor during the adjustment period
after surgery.
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Is Further Treatment Needed?
In the years after your surgery, it is important to
continue having
a rectal examination once a year and to have any symptoms checked by
your doctor.
Since surgery for BPH leaves behind a good part of the
gland, it is
still possible for prostate problems, including BPH, to develop again.
However, surgery usually offers relief from BPH for at least 15 years.
Only 10 percent of the men who have surgery for BPH eventually need a
second operation for enlargement. Usually these are men who had the
first surgery at an early age.
Sometimes, scar tissue resulting from surgery requires
treatment in
the year after surgery. Rarely, the opening of the bladder becomes
scarred and shrinks, causing obstruction. This problem may require a
surgical procedure similar to transurethral incision (see section on Surgical
Treatment).
More often, scar tissue may form in the urethra and cause narrowing.
The doctor can solve this problem during an office visit by stretching
the urethra.
Prostatic Stents
A stent is a small device that is inserted through the
urethra to
the narrowed area and allowed to expand, like a spring. The stent
pushes back the prostatic tissue, widening the urethra. It is designed
to relieve urinary obstruction in men and improve the ability to
urinate. The device is approved for use in men for whom other standard
surgical procedures to correct urinary obstruction have failed.
BPH and Prostate Cancer: No Apparent Relation
Although some of the signs of BPH and prostate cancer
are the same,
having BPH does not seem to increase the chances of getting prostate
cancer. Nevertheless, a man who has BPH may have undetected prostate
cancer at the same time or may develop prostate cancer in the future.
For this reason, the National Cancer Institute and the American Cancer
Society recommend that all men over 40 have a rectal examination once a
year to screen for prostate cancer.
After BPH surgery, the tissue removed is routinely
checked for
hidden cancer cells. In about one out of 10 cases, some cancer tissue
is found, but often it is limited to a few cells of a nonaggressive
type of cancer, and no treatment is needed.
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Hope through Research
The National Institute of Diabetes and Digestive and
Kidney Diseases
(NIDDK) was established by Congress in 1950 as one of the National
Institutes of Health (NIH), whose mission is to improve human health
through biomedical research. NIH is the research branch of the U.S.
Department of Health and Human Services.
The NIDDK conducts and supports a variety of research in
diseases of
the kidney and urinary tract. Much of the research targets disorders of
the lower urinary tract, including BPH, urinary tract infection,
interstitial cystitis, urinary obstruction, prostatitis, and urinary
stones. The knowledge gained from these studies is advancing scientific
understanding of why BPH develops and may lead to improved methods of
diagnosing and treating prostate enlargement. One such study was the MTOPS
Trial, which ended in 2003. The results are summarized above
under the Drug
Treatment section.
[Top]
Additional Reading
American Urological Association. Guideline on the
management of
benign prostatic hyperplasia: Chapter 1: Diagnosis and treatment
recommendations. The Journal of Urology.
2003;170(2 Pt 1):530–537.
National Cancer Institute. The prostate-specific antigen
(PSA) test: Questions and answers. www.cancer.gov/cancertopics/factsheet/Detection/PSA.
Reviewed August 17, 2004.
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Glossary
Anesthesia: A substance
that prevents pain from being felt, given before an operation.
Anus: The opening of the
rectum where solid waste leaves the body.
Bladder: The muscular bag
in the lower abdomen where urine is stored.
Catheter: A tube inserted
through the penis to the bladder in order to drain urine from the body.
Cystoscope: A tube-like
instrument used to view the interior of the bladder.
Ejaculation: Discharging
semen from the penis during sexual climax.
Gland: An organ that makes
and releases substances to other parts of the body.
Hormone: A substance that
stimulates the function of a gland.
Impotent: Unable to have an
erection.
Incontinence: The inability
to control urination.
Obstruction: A clog or
blockage that prevents liquid from flowing easily.
Rectum: The last part of
the large intestine (colon) ending in the anus.
Reproductive system: The
bodily systems that allow men and women to have children.
Scrotum: The sac of skin
that contains the testes.
Semen: The fluid,
containing sperm, which comes out of the penis during sexual excitement.
Sterile: Unable to father
children.
Testes: The male
reproductive glands where sperm are produced.
Ultrasound: A type of test
in which sound waves too high to hear are aimed at a structure to
produce an image of it.
Urinary tract: The path
that urine takes as it leaves the body. It includes the kidneys,
ureters, bladder, and urethra.
Urination: Discharge of
liquid waste from the body.
Urethra: The canal inside
the penis that urine passes through as it leaves the body.
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The U.S. Government does not endorse or favor any
specific
commercial product or company. Trade, proprietary, or company names
appearing in this document are used only because they are considered
necessary in the context of the information provided. If a product is
not mentioned, the omission does not mean or imply that the product is
unsatisfactory.
National Kidney and Urologic Diseases Information
Clearinghouse
3 Information Way
Bethesda, MD 20892–3580
Phone: 1–800–891–5390
TTY: 1–866–569–1162
Fax: 703–738–4929
Email: nkudic@info.niddk.nih.gov
Internet: www.kidney.niddk.nih.gov
The National Kidney and Urologic Diseases Information
Clearinghouse
(NKUDIC) is a service of the National Institute of Diabetes and
Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the
National Institutes of Health of the U.S. Department of Health and
Human Services. Established in 1987, the Clearinghouse provides
information about diseases of the kidneys and urologic system to people
with kidney and urologic disorders and to their families, health care
professionals, and the public. The NKUDIC answers inquiries, develops
and distributes publications, and works closely with professional and
patient organizations and Government agencies to coordinate resources
about kidney and urologic diseases.
Publications produced by the Clearinghouse are carefully
reviewed by both NIDDK scientists and outside experts.
This publication is not copyrighted. The Clearinghouse
encourages
users of this publication to duplicate and distribute as many copies as
desired.
NIH Publication No. 07–3012
June 2006
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