URINARY TRACT INFECTIONS IN ADULTS
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. Each year, urinary tract infections (UTI's) account
for about 8 million doctor visits. Women are especially prone to UTI's
for reasons that are poorly understood. One woman in five develops a UTI
during her lifetime.
The Urinary Tract
The urinary system consists of the kidneys, ureters, bladder, and urethra.
The key players 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.
Causes
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 live
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 UTI's
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, 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
of the immune system. Any disorder that suppresses the immune system raises
the risk of a urinary infection.
UTI's may occur in infants who are born with abnormalities of the urinary
tract, which sometimes need to be corrected with surgery. UTI's are rarely
seen in boys and young men. In women, though, the rate of UTI's 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.
Recurrent Infections
Many women suffer from frequent UTI's. 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 UTI's 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 UTI's 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 UTI's tend to have certain blood
types. Some scientists speculate that women with these blood types are
more prone to UTI's 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 UTI's.
Infections in Pregnancy
Pregnant women seem no more prone to UTI's 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.
Symptoms
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.
Diagnosis
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 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 only be detected 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
are 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.
Treatment
UTI's are treated with antibacterial drugs. The choice of drug and length
of treatment depends 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 UTI's are trimethoprim (Trimpex),
trimethoprim/sufamethoxazole (Bactrim, Septra, Cotrim), amoxicillin (Amoxil,
Trimox, Wymox), nitrofurantoin (Macrodantin, Furadantin), and ampicillin.
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 assure 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 or a warm bath 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 cancer.)
Recurrent Infections in Women
About 4 out of 5 women who have a UTI get another in 18 months. 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 appear.
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 the urine to nitrate. The test can detect about
90 percent of UTI's and may be useful for women who have recurrent infections.
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 urinate;
- 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.
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. 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.
UTI's are unusual in men. They usually stem from an obstruction -- for
example, a urinary stone or enlarged prostate -- or 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 recommended lengthier
therapy in men than in women, in part to prevent infections of the prostate
gland. Prostate infections (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.
NIH Publication No. 91-2097
|
.gif)
