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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.
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| Front view of urinary tract |
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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.
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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.
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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.
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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.
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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.
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- 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.
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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/
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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.
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NIH Publication No. 98-3195
April 1998 etext posted: 1 May 1998 |
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