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 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.
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.
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.
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.
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.
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.
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.
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.
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.)
The information contained above is intended for
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