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The organs, tubes, muscles, and nerves that work together to create, store, and carry urine are the urinary system. The urinary system includes two kidneys, two ureters, the bladder, two sphincter muscles, and the urethra.
Your body takes nutrients from food and uses them to maintain all bodily functions
including energy and self-repair. After your body has taken what it needs from the
food, waste products are left behind in the blood and in the bowel. The urinary system
works with the lungs, skin, and intestines--all of which also excrete wastes--to
keep the chemicals and water in your body balanced. Adults eliminate about a quart
and a half of urine each day. The amount depends on many factors, the major ones
being the amount of fluid and foods a person consumes and how much fluid is lost
through sweat and breathing. Certain types of medications can also affect the amount
of urine eliminated.
The urinary system removes a type of waste called urea from your blood.
Urea is produced when foods containing protein, such as meat, poultry, and certain
vegetables, are broken down in the body. Urea is carried in the bloodstream to the
kidneys.
The kidneys are bean-shaped organs about the size of your fists. They are near the
middle
of the back, just below the rib cage. The kidneys remove urea from the blood through
tiny
filtering units called nephrons. Each nephron consists of a ball formed of small
blood
capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together
with water and other waste substances, forms the urine as it passes through the nephrons
and down the renal tubules of the kidney.
From the kidneys, urine travels down two thin tubes called ureters to the bladder.
The
ureters are about 8 to 10 inches long. Muscles in the ureter walls constantly tighten
and
relax to force urine downward away from the kidneys. If urine is allowed to stand
still, or
back up, a kidney infection can develop. Small amounts of urine are emptied into
the
bladder from the ureters about every 10 to 15 seconds.
The bladder is a hollow muscular organ shaped like a balloon. It sits in your pelvis
and is
held in place by ligaments attached to other organs and the pelvic bones. The bladder
stores
urine until you are ready to go to the bathroom to empty it. It swells into a round
shape
when it is full and gets smaller when empty. If the urinary system is healthy, the
bladder
can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours.
Circular muscles called sphincters help keep urine from leaking. The sphincter muscles
close tightly like a rubber band around the opening of the bladder into the urethra,
the
tube that allows urine to pass outside the body.
Nerves in the bladder tell you when it is time to urinate (empty your bladder). As
the
bladder first fills with urine, you may notice a feeling that you need to urinate.
The
sensation to urinate becomes stronger as the bladder continues to fill and reaches
its limit.
At that point, nerves from the bladder send a message to the brain that the bladder
is full,
and your urge to empty your bladder intensifies.
When you urinate, the brain signals the bladder muscles to tighten, squeezing urine
out of
the bladder. At the same time, the brain signals the sphincter muscles to relax.
As these
muscles relax, urine exits the bladder through the urethra. When all the signals
occur in the
correct order, normal urination occurs.
Problems in the urinary system can be caused by aging, illness, or injury. As you
get
older, changes in the kidneys' structure cause them to lose some of their ability
to remove
wastes from the blood. Also, the muscles in your ureters, bladder, and urethra tend
to lose
some of their strength. You may have more urinary infections because the bladder
muscles
do not tighten enough to empty your bladder completely. A decrease in strength of
muscles
of the sphincters and the pelvis can also cause incontinence, the unwanted leakage
of urine.
Illness or injury can also prevent the kidneys from filtering the blood completely
or block
the passage of urine.
Urinalysis is a test that studies the content of urine for abnormal substances such
as
protein or signs of infection. This test involves urinating into a special container
and
leaving the sample to be studied.
Urodynamic tests evaluate the storage of urine in the bladder and the flow of urine
from
the bladder through the urethra. Your doctor may want to do a urodynamic test if
you are
having symptoms that suggest problems with the muscles or nerves of your lower urinary
system and pelvis (ureters, bladder, urethra, and sphincter muscles).
Urodynamic tests measure the contraction of the bladder muscle as it fills and empties.
The
test is done by inserting a small tube called a catheter through your urethra into
your
bladder to fill it either with water or a gas. Another small tube is inserted into
your rectum
to measure the pressure put on your bladder when you strain or cough. Other bladder
tests
use x-ray dye instead of water so that x-ray pictures can be taken when the bladder
fills and
empties to detect any abnormalities in the shape and function of the bladder. These
tests
take about an hour.
Disorders of the urinary system range in severity from easy-to-treat to life-threatening.
Benign prostatic hyperplasia (BPH) is a condition in men that affects the
prostate gland,
which is part of the male reproductive system. The prostate is located at the bottom
of the
bladder and surrounds the urethra. BPH is an enlargement of the prostate gland that
can
interfere with urinary function in older men. It causes blockage by squeezing the
urethra,
which can make it difficult to urinate. Men with BPH frequently have other bladder
symptoms including an increase in frequency of bladder emptying both during the day
and
at night. Most men over age 60 have some BPH, but not all have problems with blockage.
There are many different treatment options for BPH.
Interstitial cystitis (IC) is a chronic bladder disorder also known as painful
bladder
syndrome and frequency-urgency-dysuria syndrome. In this disorder, the bladder wall
can
become inflamed and irritated. The inflammation can lead to scarring and stiffening
of the
bladder, decreased bladder capacity, pinpoint bleeding, and, in rare cases, ulcers
in the
bladder lining. The cause of IC is unknown at this time.
Kidney stones is the term commonly used to refer to stones, or calculi, in
the urinary
system. Stones form in the kidneys and may be found anywhere in the urinary system.
They vary in size. Some stones cause great pain while others cause very little. The
aim of
treatment is to remove the stones, prevent infection, and prevent recurrence. Both
nonsurgical and surgical treatments are used. Kidney stones affect men more often
than
women.
Prostatitis is inflammation of the prostate gland that results in urinary frequency
and
urgency, burning or painful urination (dysuria), and pain in the lower back and genital
area, among other symptoms. In some cases, prostatitis is caused by bacterial infection
and
can be treated with antibiotics. But the more common forms of prostatitis are not
associated
with any known infecting organism. Antibiotics are often ineffective in treating
the
nonbacterial forms of prostatitis.
Proteinuria is the presence of abnormal amounts of protein in the urine. Healthy
kidneys
take wastes out of the blood but leave in protein. Protein in the urine does not
cause a
problem by itself. But it may be a sign that your kidneys are not working properly.
Renal (kidney) failure results when the kidneys are not able to regulate water
and
chemicals in the body or remove waste products from your blood. Acute renal failure
(ARF) is the sudden onset of kidney failure. This can be caused by an accident that
injures the kidneys, loss of a lot of blood, or some drugs or poisons. ARF may lead
to
permanent loss of kidney function. But if the kidneys are not seriously damaged,
they may
recover. Chronic renal failure (CRF) is the gradual reduction of kidney function
that may
lead to permanent kidney failure, or end-stage renal disease (ESRD). You may go several
years without knowing you have CRF.
Urinary tract infections (UTIs) are caused by bacteria in the urinary tract.
Women get
UTIs more often than men. UTIs are treated with antibiotics. Drinking lots of fluids
also
helps by flushing out the bacteria.
The name of the UTI depends on its location in the urinary tract. An infection in
the
bladder is called cystitis. If the infection is in one or both of the kidneys, the
infection is
called pyelonephritis. This type of UTI can cause serious damage to the kidneys if
it is
not adequately treated.
Urinary incontinence, loss of bladder control, is the involuntary passage
of urine. There
are many causes and types of incontinence, and many treatment options. Treatments
range
from simple exercises to surgery. Women are affected by urinary incontinence more
often
than men.
Urinary retention, or bladder-emptying problems, is a common urological problem
with
many possible causes. Normally, urination can be initiated voluntarily and the bladder
empties completely. Urinary retention is the abnormal holding of urine in the bladder.
Acute urinary retention is the sudden inability to urinate, causing pain and discomfort.
Causes can include an obstruction in the urinary system, stress, or neurologic problems.
Chronic urinary retention refers to the persistent presence of urine left in the
bladder after
incomplete emptying. Common causes of chronic urinary retention are bladder muscle
failure, nerve damage, or obstructions in the urinary tract. Treatment for urinary
retention
depends on the cause.
Your primary doctor can help you with some urinary problems. Your pediatrician may
be
able to treat some of your child's urinary problems. But some problems may require
the
attention of a urologist, a doctor who specializes in treating problems of the urinary
system and the male reproductive system. A gynecologist is a doctor who specializes
in
the female reproductive system and may be able to help with some urinary problems.
A
urogynecologist is a gynecologist who specializes in the female urinary system. A
nephrologist specializes in treating diseases of the kidney.
Your urinary system filters waste and extra fluid from your blood.
Problems in the urinary system include kidney failure, urinary tract infections,
kidney stones, prostate enlargement, and bladder control problems.
Health professionals who treat urinary problems include general practitioners
(your primary doctor), pediatricians, urologists, gynecologists, urogynecologists,
and nephrologists.
American Foundation for Urologic Disease
1128 N. Charles Street
Baltimore, MD 21201
(800) 242-2383 or (410) 468-1800
admin@afud.org
http://www.access.digex.net/~afud
American Kidney Fund
6110 Executive Boulevard
Suite 100
Rockville, MD 20852
(800) 638-8299 or (301) 881-3052
helpline@akfinc.org
American Society of Pediatric Nephrology
Department of Pediatrics
University of Wisconsin Children's Hospital
600 Highland Avenue
Madison, WI 53792-4108
(608) 265-6020
American Uro-Gynecologic Society
401 North Michigan Avenue
Chicago, IL 60611-4267
(312) 644-6610 ext. 4712
Interstitial Cystitis Association
P.O. Box 1553
Madison Square Station
New York, NY 10159
(800) ICA-1626 or (212) 979-6057
http://www.ichelp.org
National Association for Continence (NAFC)
P.O. Box 8310
Spartanburg, SC 29305-8310
(864) 579-7900 or (800) BLADDER
http://www.nafc.org/
National Kidney Foundation
30 East 33rd Street
New York, NY 10016
(800) 622-9010
http://www.kidney.org/
The Prostatitis Foundation
Information Distribution Center
Parkway Business Center
2029 Ireland Grove Road
Bloomington, IL 61704
(309) 664-6222
Mcapstone@aol.com
http://www.prostate.org/
The Simon Foundation for Continence
P.O. Box 835
Wilmette, IL 60091
(800) 23-SIMON or
(847) 864-3913 (main office)
simoninfo@simonfoundation.org
http://www.simonfoundation.org/
National Kidney and Urologic Diseases Information
Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
E-mail: nkudic@info.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 under the U.S. Department
of
Health and Human Service. 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. NKUDIC
answers inquiries; develops, reviews, 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 for scientific
accuracy,
content, and readability.
This etext is not copyrighted. The clearinghouse encourages users of this epub to
duplicate
and distribute as many copies as desired.
NIH Publication No. 98-3195
April 1998
etext posted: 1 May 1998
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