Your Urinary
System and How It Works
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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.
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.afud.org/
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/html/index.html
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).
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