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The urinary system consists of the kidneys,
ureters, bladder, and urethra. The key elements in the system are the kidneys, a pair of purplish-brown organs located below the
ribs toward the middle of the back.
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The kidneys remove excess liquid and wastes from
the blood in the form of urine, keep a stable balance of salts and other substances in the
blood, and produce a hormone that aids the formation of red blood cells.
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Narrow tubes
called ureters carry urine from the kidneys to the bladder, a triangle-shaped chamber in
the lower abdomen. Urine is stored in the bladder and emptied through the urethra.
The average adult passes about a quart and a half of urine each day.
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The amount of urine
varies, depending on the fluids and foods a person consumes. The volume formed at night
is about half that formed in the daytime. What are the causes of
UTI? Normal urine is sterile. It contains fluids, salts, and waste products, but it is free of
bacteria, viruses, and fungi.
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An infection occurs when
microorganisms, usually bacteria from the digestive tract, cling to the opening of the urethra and begin
to multiply.
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Most infections arise from one type of bacteria, Escherichia coli (E.
coli), which normally lives in the colon. In most cases, bacteria first begin growing in the urethra. An infection limited to the
urethra is called urethritis.
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From there bacteria often move on to the bladder, causing a
bladder infection (cystitis). If the infection is not treated promptly, bacteria may then go
up the ureters to infect the kidneys (pyelonephritis).
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Microorganisms called Chlamydia and Mycoplasma may also cause UTIs in both men
and women, but these infections tend to remain limited to the urethra and reproductive
system.
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Unlike E.
coli, Chlamydia and Mycoplasma may be sexually transmitted, and infections require treatment
of both partners. The urinary system is structured in a way that helps ward off infection. The ureters and
bladder normally prevent urine from backing up toward the kidneys, and the flow of
urine from the bladder helps wash bacteria out of the body.
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In men, the prostate gland
produces secretions that slow bacterial growth. In both sexes, immune defenses also
prevent infection. But despite these safeguards, infections still occur.
Who is at risk? Some people are more prone to getting a UTI than others.
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Any
abnormality of the urinary tract that obstructs the flow of urine (a kidney stone, for example) sets the
stage for an infection. An enlarged prostate gland also can slow the flow of urine, thus raising the risk
of infection. A common source of infection is catheters, or tubes, placed in the bladder.
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A person who
cannot void or who is unconscious or critically ill often needs a catheter that stays in
place for a long time. Some people, especially the elderly or those with nervous system
disorders who lose bladder control, may need a catheter for life.
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Bacteria on the catheter
can infect the bladder, so hospital staff take special care to keep the catheter sterile and
remove it as soon as possible. People with diabetes have a higher risk of a UTI because of changes in the immune
system. Any disorder that suppresses the immune system raises the risk of a urinary
infection. UTIs may occur in infants who are born with abnormalities of the urinary tract, which
sometimes need to be corrected with surgery.
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UTIs are rarely
seen in boys and young men. In women, though, the rate of UTIs gradually increases with age. Scientists are not
sure why women have more urinary infections than men. One factor may be that a
woman's urethra is short, allowing bacteria quick access to the bladder. Also, a woman's
urethral opening is near sources of bacteria from the anus and vagina.
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For many women,
sexual intercourse seems to trigger an infection, although the reasons for this linkage are
unclear. According to several studies, women who use a diaphragm are more likely to develop a
UTI than women who use other forms of birth control.
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Recently, researchers found that
women whose partners use a condom with spermicidal foam also tend to have growth of
E. coli bacteria in the vagina. Recurrent Infections Many women suffer from frequent
UTIs. Nearly 20 percent of women who have a UTI will have another, and 30 percent of those will have yet another. Of the last group, 80
percent will have recurrences.
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Usually, the latest infection stems from a strain or type of bacteria that is different from
the infection before it, indicating a separate infection. (Even when several UTIs in a row
are due to E. coli, slight differences in the bacteria indicate distinct infections.)
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Research funded by the National Institutes of Health
(NIH) suggests that one factor behind recurrent UTIs may be the ability of bacteria to attach to cells lining the urinary
tract. A recent NIH-funded study found that bacteria formed a protective film on the
inner lining of the bladder in mice.
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If a similar process can be demonstrated in humans,
the discovery may lead to new treatments to prevent recurrent
UTIs. Another line of research has indicated that women who are "non-secretors" of certain blood group
antigens may be more prone to recurrent UTIs because the cells lining the vagina and
urethra may allow bacteria to attach more easily.
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Further
research will show whether this association is sound and proves useful in identifying women at high risk for
UTIs. Infections in Pregnancy Pregnant women seem no more prone to UTIs than other women. However, when a UTI
does occur, it is more likely to travel to the kidneys. According to some reports, about 2
to 4 percent of pregnant women develop a urinary infection.
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Scientists think that
hormonal changes and shifts in the position of the urinary tract during pregnancy make it
easier for bacteria to travel up the ureters to the kidneys. For this reason, many doctors
recommend periodic testing of urine. What are the symptoms of
UTI? Not everyone with a UTI has symptoms, but most people get at least some.
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These may
include a frequent urge to urinate and a painful, burning feeling in the area of the bladder
or urethra during urination. It is not unusual to feel bad all over--tired, shaky, washed out-
-and to feel pain even when not urinating. Often women feel an uncomfortable pressure
above the pubic bone, and some men experience a fullness in the rectum.
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It is common
for a person with a urinary infection to complain that, despite the urge to
urinate, only a small amount of urine is passed. The urine itself may look milky or cloudy, even reddish
if blood is present. A fever may mean that the infection has reached the kidneys. Other
symptoms of a kidney infection include pain in the back or side below the ribs, nausea, or
vomiting.
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In children,
symptoms of a urinary infection may be overlooked or attributed to another
disorder. A UTI should be considered when a child or infant seems irritable, is not eating
normally, has an unexplained fever that does not go away, has incontinence or loose
bowels, or is not thriving. The child should be seen by a doctor if there are any questions
about these symptoms, especially a change in the child's urinary pattern.
How is UTI diagnosed?
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To find out whether you have a
UTI, your doctor will test a sample of urine for pus and bacteria. You will be asked to give a "clean catch" urine sample by washing the genital
area and collecting a "midstream" sample of urine in a sterile container. (This method of
collecting urine helps prevent bacteria around the genital area from getting into the
sample and confusing the test results.)
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Usually, the sample is sent to a laboratory,
although some doctors' offices are equipped to do the testing. In the urinalysis test, the urine is examined for white and red blood cells and bacteria.
Then the bacteria are grown in a culture and tested against different antibiotics to see
which drug best destroys the bacteria. This last step is called a sensitivity test.
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Some microbes, like Chlamydia and
Mycoplasma, can be detected only with special bacterial cultures. A doctor suspects one of these
infections when a person has symptoms of a UTI and pus in the urine, but a standard culture fails to grow any bacteria.
When an infection does not clear up with treatment and is traced to the same strain
of bacteria, the doctor will order a test that makes images of the urinary tract.
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One of these
tests is an intravenous pyelogram (IVP), which gives x-ray images of the bladder,
kidneys, and ureters. An opaque dye visible on x-ray film is injected into a vein, and a
series of x rays is taken. The film shows an outline of the urinary tract, revealing even
small changes in the structure of the tract.
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If you have recurrent infections, your doctor also may recommend an ultrasound exam,
which gives pictures from the echo patterns of sound waves bounced back from internal
organs. Another useful test is cystoscopy. A cystoscope is an instrument made of a
hollow tube with several lenses and a light source, which allows the doctor to see inside
the bladder from the urethra.
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How is UTI treated?
UTIs are treated with antibacterial drugs. The choice of drug and length of treatment
depend on the patient's history and the urine tests that identify the offending bacteria. The
sensitivity test is especially useful in helping the doctor select the most effective drug.
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The drugs most often used to treat routine, uncomplicated UTIs are trimethoprim
(Trimpex), trimethoprim/sulfamethoxazole (Bactrim, Septra,
Cotrim), amoxicillin (Amoxil, Trimox, Wymox), nitrofurantoin (Macrodantin,
Furadantin), and ampicillin. A class of drugs called quinolones includes four drugs approved in recent years for treating
UTI.
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These drugs include ofloxacin
(Floxin), norfloxacin (Noroxin), ciprofloxacin (Cipro), and trovafloxin
(Trovan). Often, a UTI can be cured with 1 or 2 days of treatment if the infection is not complicated
by an obstruction or nervous system disorder.
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Still, many doctors ask their patients to
take antibiotics for a week or two to ensure that the infection has been cured. Single-dose
treatment is not recommended for some groups of patients, for example, those who have
delayed treatment or have signs of a kidney infection, patients with diabetes or structural
abnormalities, or men who have prostate infections.
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Longer treatment is also needed by
patients with infections caused by Mycoplasma or Chlamydia, which are usually treated
with tetracycline, trimethoprim/sulfamethoxazole (TMP/SMZ), or
doxycycline.
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A followup
urinalysis helps to confirm that the urinary tract is infection- free. It is important to
take the full course of treatment because symptoms may disappear before the infection is
fully cleared. Severely ill patients with kidney infections may be
hospitalized until they can take fluids and needed drugs on their own. Kidney infections generally require
several weeks of antibiotic treatment.
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Researchers at the University of Washington found that 2-week
therapy with TMP/SMZ was as effective as 6 weeks of treatment with the same drug in
women with kidney infections that did not involve an obstruction or nervous system
disorder. In such cases, kidney infections rarely lead to kidney damage or kidney failure
unless they go untreated.
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Various drugs are available to relieve the pain of a
UTI. A heating pad may also help. Most doctors suggest that drinking
plenty of water helps cleanse the urinary tract of bacteria. During treatment, it is best to avoid coffee, alcohol, and spicy foods. And one of
the best things a smoker can do for his or her bladder is to quit smoking. Smoking is the
major known cause of bladder cancer. Recurrent Infections in Women
Women who have had three UTIs are likely to continue having them.
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Four out of five
such women get another within 18 months of the last UTI. Many women have them even
more often. A woman who has frequent recurrences (three or more a year) should ask her
doctor about one of the following treatment options: Take low doses of an antibiotic such as
TMP/SMZ or nitrofurantoin daily for 6 months or longer.
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(If taken
at bedtime, the drug remains in the bladder longer and may be more effective.)
NIH-supported research at the University of Washington has shown this therapy to be effective without causing serious side
effects. Take a single dose of an antibiotic after sexual intercourse.
Take a short course (1 or 2 days) of antibiotics when symptoms appear.
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Dipsticks that change color when an infection is present are now available without a
prescription. The strips detect nitrite, which is formed when bacteria change nitrate in the
urine to nitrite. The test can detect about 90 percent of UTIs when used with the first
morning urine specimen and may be useful for women who have recurrent infections.
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Doctors suggest some additional steps that a woman can take on her own to avoid an
infection: Drink plenty of water every day. Urinate when you feel the need; don't resist the urge to urinate.
Wipe from front to back to prevent bacteria around the anus from entering the
vagina or urethra. Take showers instead of tub baths.
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Cleanse the genital area before sexual intercourse.
Avoid using feminine hygiene sprays and scented douches, which may irritate the
urethra. Some doctors suggest drinking cranberry juice. Infections in Pregnancy
A pregnant woman who develops a UTI should be treated promptly to avoid premature
delivery of her baby and other risks such as high blood pressure.
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Some antibiotics are not
safe to take during pregnancy. In selecting the best treatments, doctors consider various
factors such as the drug's effectiveness, the stage of pregnancy, the mother's health, and
potential effects on the fetus. Complicated Infections Curing infections that stem from a urinary obstruction or nervous system disorder
depends on finding and correcting the underlying problem, sometimes with surgery.
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If the
root cause goes untreated, this group of patients is at risk of kidney damage. Also, such
infections tend to arise from a wider range of bacteria, and sometimes from more than
one type of bacteria at a time. Infections in Men UTIs in men usually stem from an obstruction--for example, a urinary stone or enlarged
prostate--or from a medical procedure involving a catheter.
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The first step is to identify the
infecting organism and the drugs to which it is sensitive. Usually, doctors recommend
lengthier therapy in men than in women, in part to prevent infections of the prostate
gland. Prostate infections (chronic bacterial prostatitis) are harder to cure because antibiotics are
unable to penetrate infected prostate tissue effectively.
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For this reason, men with
prostatitis often need long-term treatment with a carefully selected
antibiotic. UTIs in older men are frequently associated with acute bacterial
prostatitis, which can be fatal if not treated immediately. Is there a vaccine to prevent recurrent
UTIs?
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In the future, scientists may
develop a vaccine that can prevent UTIs from coming back. Researchers in different studies have found that children and women who tend to get
UTIs repeatedly are likely to lack proteins called
immunoglobulins, which fight infection.
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Children and women who do not get UTIs are more likely to have
normal levels of immunoglobulins in their genital and urinary tracts.
Early tests indicate that a vaccine helps patients build up their own natural infectionfighting
powers.
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The dead bacteria in the vaccine do
not spread like an infection; instead, they prompt the body to produce antibodies that can later fight against live organisms.
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Researchers are testing injected and oral vaccines to see which works best.
Another method being considered for women is to apply the vaccine directly as a suppository in
the vagina.
