Urinary tract infection introduction
Urinary tract infections are a serious health problem affecting millions of people each year.
Infections of the urinary tract are the second most common type of infection in the body. Urinary tract infections (UTIs) account for about 8.3 million doctor visits each year. Women are especially prone to UTIs for reasons that are not yet well understood. One woman in five develops a UTI during her lifetime. UTIs in men are not as common as in women but can be very serious when they do occur.
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 excess liquid and wastes 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 sack-like organ 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 UTI?
Normally, urine is sterile. It is usually free of bacteria, viruses, and fungi but does contain fluids, salts, and waste products. An infection occurs when tiny organisms, usually bacteria from the digestive tract, cling to the opening of the urethra and begin to multiply. The urethra is the tube that carries urine from the bladder to outside the body. Most infections arise from one type of bacteria, Escherichia coli (E. coli), which normally lives in the colon.
In many cases, bacteria first travel to the urethra. When bacteria multiply, an infection can occur. An infection limited to the urethra is called urethritis. If bacteria move to the bladder and multiply, a bladder infection, called cystitis, results. 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. 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. But despite these safeguards, 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 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. 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 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 infections.
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 found that bacteria formed a protective film on the inner lining of the bladder in mice. If a similar process can be demonstrated in humans, the discovery may lead to new treatments to prevent recurrent UTIs. Another line of research has indicated that women who are "non-secretors" of certain blood group antigens may be more prone to recurrent 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 in a pregnant woman, 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 during pregnancy.
What are the symptoms of 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
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.
How is a 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 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, 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 (Omnipen, Polycillin, Principen, Totacillin). 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 (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.
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. 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 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 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 a 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 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.
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 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.
Infections in men
UTIs in men are often a result of an
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.
Is there a vaccine to prevent recurrent UTIs?
In the future, scientists may develop a vaccine that can prevent UTIs from coming back. Researchers in different studies have found that children and women who tend to get UTIs 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 injected 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.
For more information
American Urological Association
1000 Corporate Boulevard
Linthicum, MD 21090
Phone: 1-866-RING–AUA (746-4282) or 410-689-3700
Fax: 410-689-3800
Email: aua@auanet.org
Internet: www.urologyhealth.org
The Prostatitis Foundation
1063 30th Street, Box 8
Smithshire, IL 61478
Phone: 1-888-891-4200
Fax: 309-325-7184
Email: mcapston@aol.com
Internet: www.prostatitis.org
Urinary Tract Infection in Adults At A Glance
- The urinary tract consists of the kidneys, ureters, bladder, and urethra.
- Some people are at more risk for urinary tract infections (UTIs) than others.
- One woman in five develops a UTI during her lifetime.
- Not everyone with a UTI has symptoms. Common symptoms include a frequent urge to urinate and a painful, burning when urinating.
- Underlying conditions that impair the normal urinary flow can lead to more complicated UTIs.
What is a urinalysis?
A urinalysis is simply an analysis of the urine. It is a very common test that can be performed in many healthcare settings including doctors' offices, urgent care facilities, laboratories, and hospitals.
It is performed by collecting a urine sample from the patient in a specimen cup. Usually only small amounts (10-15 ml's) may be required for urinalysis testing.
What can a urinalysis show?
Urinalysis can disclose evidence of diseases, even some that have not caused significant signs or symptoms. Therefore, a urinalysis is commonly a part of routine health screening.
Urinalysis is also a very useful test that may be ordered by your physician for particular reasons. Urinalysis is commonly used to diagnose a urinary tract or kidney infection, to evaluate causes of kidney failure, to screen for progression of some chronic conditions such as diabetes mellitus and high blood pressure (hypertension).
It also may be used in combination with other tests to diagnose some diseases. Examples of this include kidney stones, inflammation of the kidneys (glomerulonephritis), or muscle break breakdown (rhabdomyolysis).
Interpretation of urinalysis is generally based on reviewing all the components of the test as well as the clinical symptoms and signs of the patient.
What does urinalysis involve?
Urinalysis is done by collecting a urine sample from a patient. The optimal sample tends to be an early morning urine sample because it is frequently the most concentrated urine produced in the day.
Methods of collection are slightly different for female and male patient.
- For females, the patient is asked to clean the area around the urethra with a special cleansing wipe, by spreading the labia of the external genitals and cleaning from front to back (toward the anus).
- For men, the tip of the penis may be wiped with a cleansing pad prior to collection.
- The urine is then collected in a clean urine specimen cup while the patient is urinating. It is best to avoid collecting the initial stream of urine. After the initial part of urine is disposed of in the toilet, then the urine is collected in the urine container provided. Once about 10-15 ml (roughly 3-4 tablespoons) are collected in the container for testing, the remainder of the urine may be voided in the toilet again. This is called the clean catch or the midstream urine collection.
The collected urine sample should be taken to the laboratory for analysis, typically within one hour of collection. If transportation to the lab could take more than one hour, then the sample may be refrigerated.
In some patients who are unable to void spontaneously or those who are not able to follow instructions other methods may be used, such as placing a catheter (a small rubber tube) through the outside opening to the bladder (urethra) to collect the sample directly from the bladder.
What is macroscopic urinalysis?
Macroscopic urinalysis is the direct visual observation of the urine, noting its quantity, color, clarity or cloudiness, etc.
Normal urine is typically light yellow and clear without any cloudiness. Obvious abnormalities in the color, clarity, and cloudiness may suggest possibility of an infection, dehydration, blood in the urine (hematuria), liver disease, breakdown of muscle or red blood cells in the body. Certain medications may also change the color of urine. Very foamy urine may represent large amounts of protein in the urine (proteinuria).What is urine dipstick chemical analysis?
Urine dipstick is a narrow plastic strip which has several squares of different colors attached to it. Each small square represents a component of the test used to interpret urinalysis. The entire strip is dipped in the urine sample and color changes in each square are noted. The color change takes place after several seconds to a few minutes from dipping the strip. If read too early or too long after the strip is dipped, the results may not be accurate.
The squares on the dipstick represent the following components in the urine:
- specific gravity (concentration of urine),
- acidity of the urine (pH),
- protein in the urine (mainly albumin),
- glucose (sugar),
- ketones (products of fat metabolism),
- blood, leukocyte esterase (produced by white blood cells in urine),
- nitrite (produced by bacteria in urine),
- bilirubin (possible liver disease or red blood cell breakdown), and
- urobilinogen (possible liver disease).
Presence or absence of each of these color changes on the strip provides important clues for your doctor to make clinical decisions based on the urinalysis results.
What are the pros and cons of dip sticks?
The main advantage of dipsticks is that they are convenient, easy to interpret, and cost-effective for urinalysis testing. They can be analyzed within minutes of urine collection in the doctor's office or in the emergency room to provide valuable information.
However, what can be learned from a dipstick is limited by the design of the dipstick. The main disadvantage is that the information may not be very accurate as the test is time-sensitive. It also provides limited information about the urine as it is qualitative test and not a quantitative test (for example, it does not give a precise measure of the quantity of abnormality).
What is microscopic urinalysis?
The microscopic urinalysis is the study of the urine under the microscope. It requires only a relatively inexpensive light microscope. Cells and cellular debris, bacteria, and crystals in the urine can detected by this examination to provide further clinical clues.
How is microscopic urinalysis done?
Microscopic urinalysis is done simply pouring the urine sample into a test tube and centrifuging it (spinning it down in a machine) for a few minutes. The top liquid part (the supernatant) is discarded. The solid part left in the bottom of the test tube (the urine sediment) is mixed with the remaining drop of urine in the test tube and one drop is analyzed under a microscope.
First, the sediment is examined through the microscope under low-power to identify what are called casts, crystals, squamous (flat) cells, and other large objects.
Examination is then performed through the microscope at high power to further identify any cells, bacteria and clumps of cells or debris called casts.
What kind of cells can be detected?
Epithelial (flat cells) and red and white blood cells may be seen in the urine.
Sometimes cells, cellular debris, and casts are seen in the microscopic urinalysis. Epithelial cells (cells in the lining of the bladder or urethra) may suggest inflammation within the bladder, but they also may originate form the skin and could be contamination.
Casts and cellular debris originate from higher up in the urinary tract, such as in the kidneys. These are material shed from kidney cell lining and travel down through the urinary tubes. These usually suggest an injury to the kidney from an inflammation or lack of blood flow to the kidneys. Rarely, tumor cells can be in the urine suggesting a urinary tract cancer.
What can the presence of red blood cells in the urine mean?
Red blood cells can enter the urine from the vagina in menstruation or from the trauma of bladder catherization.
A high count of red blood cells in the urine can indicate infection, trauma, tumors, kidney stones. If red blood cells seen under microscopy look distorted, they suggest kidney as the possible source and may arise due to kidney inflammation (glomerulonephritis). Small amounts of red blood cells in the urine are sometimes seen young healthy people and not indicative of any disease.
What can the presence of white blood cells in the urine mean?
Urine is a generally thought of as a sterile body fluid, therefore, evidence of white blood cells or bacteria in the urine is considered abnormal and may suggest a urinary tract infection such as, bladder infection (cystitis), infection of kidney (pyelonephritis). White blood cells may be detected in the urine through a microscopic examination (pyuria or leukocytes in the blood). They can be seen under high power field and the number of cells are recorded (quantitative).
White cells from the vagina or the opening of the urethra (in males, too) can contaminate a urine sample. Such contamination aside, the presence of abnormal numbers of white blood cells in the urine is significant.
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