Urine is normally sterile. It is usually free of bacteria, viruses, and fungi
A urinary tract infection (UTI) occurs when tiny organisms, usually bacteria from the digestive tract, infect the urinary system and urine.
Most infections arise from one type of bacteria, Escherichia coli (E. coli), which normally lives in the colon.
In many cases, the bacteria first travel through the urethra into the bladder. An infection of the urethra only is called. An infection that moves to the bladder is called cystitis. If the infection is not treated promptly, bacteria may then travel further up the ureters to multiply and infect the kidneys. A kidney infection is called 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.
Risks of Developing a UTI
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 urethra and 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 clean 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 other disorder that suppresses the immune system raises the risk of a urinary infection.
UTIs may occur in infants, both boys and girls, who are born with abnormalities of the urinary tract, which sometimes need to be corrected with surgery. UTIs are more rare in boys and young men. In adult women, though, the rate of UTIs gradually increases with age. It is not clear 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.
Symptoms of a UTI
Not everyone with a UTI has symptoms, but most people get at least some symptoms. 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. Normally, a UTI does not cause fever if it is in the bladder or urethra. 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. Unlike adults, children are more likely to have fever and no other symptoms. This can happen to both boys and girls. 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.
Diagnosis of a Urinary Tract Infection
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 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 may order some tests to determine if your system is normal. 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.
UTIs are treated with antibiotics. 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/sulfamethoxazole (Bactrim, Septra,), amoxicillin, nitrofurantoin, and ampicillin. A class of drugs called quinolones includes four drugs approved in recent years for treating UTI. These drugs include ofloxacin, norfloxacin, 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 other 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.
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 Urinatry Tract 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) can 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 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 a prescription. The strips detect nitrite, which is formed when bacteria change nitrate in the urine to nitrite. The at-home test can detect about 90% of UTIs when used with the first morning urine specimen 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.
- 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.
- Some doctors suggest drinking cranberry juice.
UTIs During 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 Urinary Tract Infections
Curing infections that stem from a urinary obstruction or other systemic disorders 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.
Urinary Tract Infections in Men
UTIs in men are often a result of 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 have serious consequences if not treated urgently.