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 UTIs 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
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
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 UTI?
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
UTIs 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 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. 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 UTI 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 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.
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 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. 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 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.
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
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 has also shown that women with recurrent UTIs 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 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. 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. 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 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
if there is a change in the child's urinary pattern.
How Is UTI Diagnosed?
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.) Usually, the sample is sent to
a laboratory, although some doctors' offices are equipped to do
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
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 tract.
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 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. 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. These drugs include ofloxacin (Floxin),
norfloxacin (Noroxin), ciprofloxacin (Cipro), and trovafloxin
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. 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 UTI. 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 UTIs are likely to continue having
them. 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. (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
Dipsticks that change color when an infection is present are
now available without 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
Doctors suggest some additional steps that a woman can take on
her own to avoid an infection:
- Drink plenty of water every day. Some doctors suggest drinking
cranberry juice, which in large amounts inhibits the growth
of some bacteria by acidifying the urine. Vitamin C (ascorbic
acid) supplements have the same effect.
- Urinate when you feel the need; don't resist the urge to
- 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.
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. 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.
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
UTIs 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.
UTIs in older men are frequently associated with acute bacterial
prostatitis, which can be fatal if not treated immediately.
Other Sources of Information
American Foundation for Urologic Disease
1128 North Charles Street
Baltimore, MD 21201
Phone: 1-800-242-2383 or (410) 727-2908
The Prostatitis Foundation
1063 30th Street, Box 8
Smithshire, IL 61478
Fax: (309) 325-7184