Urinary Tract Infections
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The urinary tract
Urinary tract infections are a serious health problem
affecting millions of people each year.
Infections of the urinary tract are common--only
respiratory infections occur more often. In 1997, urinary
tract infections (UTIs) accounted for about 8.3 million
doctor visits.* Women are
especially prone to Urinary Tract infections for reasons
that are poorly understood. One woman in five develops a UTI
during her lifetime. UTIs in men are not so common, but they
can be very serious when they do occur.
*Ambulatory Care Visits
to Physician Offices, Hospital Outpatient Departments, and
Emergency Departments: United States, 1997.
GA: National Center for Health Statistics, Centers for
Disease Control and Prevention, U.S. Dept. of Health and
Human Services; November 1999. Vital and Health
Statistics. Series 13, No. 143.
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. The kidneys remove
liquid waste 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. 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. 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 Urinary Tract infection?
Normal urine is sterile. It contains fluids, salts, and
waste products, but it is free of bacteria, viruses, and
fungi. An infection occurs when microorganisms, usually
bacteria from the digestive tract, cling to the opening of
the urethra and begin to multiply. 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. 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).
Microorganisms called Chlamydia and Mycoplasma
may also cause Urinary Tract infections in both men and
women, but these infections tend to remain limited to the
urethra and reproductive system. Unlike E. coli,
Chlamydia and Mycoplasma may be sexually
transmitted, and infections require treatment of both
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.
In men, the prostate gland produces secretions that slow
bacterial growth. In both sexes, immune defenses also
prevent infection. Despite these safeguards, though,
infections still occur.
Who is at risk?
Some people are more prone to getting a Urinary Tract
infection than others. 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. 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. 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 Urinary
Tract infection because of changes in the immune system. Any
disorder that suppresses the immune system raises the risk
of a urinary infection.
Urinary Tract infections may occur in infants who are
born with abnormalities of the urinary tract, which
sometimes need to be corrected with surgery. 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. For many women, sexual intercourse seems to trigger
an infection, although the reasons for this linkage are
According to several studies, women who use a diaphragm
are more likely to develop a Urinary Tract infection than
women who use other forms of birth control. 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.
Many women suffer from frequent Urinary Tract infections.
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.
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 Urinary
Tract infections in a row are due to E. coli, slight
differences in the bacteria indicate distinct infections.)
Research funded by the National Institutes of Health (NIH)
suggests that one factor behind recurrent Urinary Tract
infections may be the ability of bacteria to attach to cells
lining the urinary tract. A recent NIH-funded study has also
shown that women with recurrent Urinary Tract infections
tend to have certain blood types. Some scientists speculate
that women with these blood types are more prone to UTIs
because the cells lining the vagina and urethra may allow
bacteria to attach more easily. Further research will show
whether this association is sound and proves useful in
identifying women at high risk for Urinary Tract infections.
Infections in Pregnancy
Pregnant women seem no more prone to Urinary Tract
infections 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. 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 Urinary Tract infection?
Not everyone with a Urinary Tract infection has symptoms,
but most people get at least some. 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. 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.
In children, symptoms of a urinary infection may be
overlooked or attributed to another disorder. A Urinary
Tract infection 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 if there is a change in the child's urinary
How is Urinary Tract infection diagnosed?
To find out whether you have a Urinary Tract infection,
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.) 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.
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. 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
If you have recurrent infections, your doctor also may
recommend an ultrasound exam, which gives pictures from the
echo patterns of soundwaves 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.
How is Urinary Tract infection treated?
Urinary Tract infections 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.
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 Urinary Tract
infection. These drugs include ofloxacin (Floxin),
norfloxacin (Noroxin), ciprofloxacin (Cipro), and
Often, a Urinary Tract infection can be cured with 1 or 2
days of treatment if the infection is not complicated by an
obstruction or nervous system disorder. 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. 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. 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. 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.
Various drugs are available to relieve the pain of a
Urinary Tract infection. A heating pad may also help. Most
doctors suggest that drinking plenty of water helps cleanse
the urinary tract of bacteria. For the time being, 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
Recurrent Infections in Women
Women who have had three Urinary Tract infections are
likely to continue having them. Four out of five such women
get another within 18 months of the last Urinary Tract
infection. 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. (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
- Take a short course (1 or 2 days) of antibiotics when
Dipsticks that change color when an infection is present
are now available without rescription. The strips detect
nitrite, which is formed when bacteria change nitrate in the
urine to nitrite. The test can detect about 90 percent of
Urinary Tract infections when used with the first morning
urine specimen and may be useful for women who have
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
- Wipe from front to back to prevent bacteria around the
anus from entering the vagina or urethra.
- Take showers instead of tub baths.
- 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 Urinary Tract infection
should be treated promptly to avoid premature delivery of
her baby and other risks such as high blood pressure. 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
Curing infections that stem from a urinary obstruction or
nervous system disorder depends on finding and correcting
the underlying problem, sometimes with surgery. 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
Urinary Tract infections in men usually stem from an
obstruction--for example, a urinary stone or enlarged
prostate--or from a medical procedure involving a catheter.
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. For this reason, men
with prostatitis often need long-term treatment with a
carefully selected antibiotic. Urinary Tract infections 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 Urinary Tract
In the future, scientists may develop a vaccine that can
prevent Urinary Tract infections from coming back.
Researchers in different studies have found that children
and women who tend to get Urinary Tract infections
repeatedly are likely to lack proteins called
immunoglobulins, which fight infection. 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 infection-fighting powers. 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. Researchers are testing
injection 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.