Bladder infections are among the most common of all infections and can occur at any time in your life.  Nearly all urinary tract infections are mild, treatable, and have no long-term consequences.  Serious physical complications can occur in some cases, however, most often in hospitalized patients.

Causes

Usually, a UTI is caused by bacteria that can also live in the digestive tract, in the vagina, or around the urethra, which is at the entrance to the urinary tract. Most often these bacteria enter the urethra from the rectum and travel to the bladder and kidneys, your body removes the bacteria, and you have no symptoms. Some people seem to be prone to infection, including women and older people.

Risk Factors

UTIs are among the most common medical complaints by women in their reproductive years. An estimated 7 million episodes of UTI occur each year in the United States, although the actual rate may be higher. UTIs can be especially dangerous for older people and pregnant women when they involve the kidney (pyelonephritis) where the organisms may cause blood poisoning.  UTIs can also pose problems for those with diabetes and those who have difficulty urinating.

On average, 10 to 20 percent of all women will develop a urinary tract infection at some time in their lives and 20 percent of those will have recurrent UTIs. The risk for UTIs, both symptomatic and asymptomatic, is highest after menopause.

Among the risk factors for women:

Structure of the Female Urinary Tract. The female urethra is relatively short - one and one half inches compared to eight inches in men. Bacteria from fecal matter can also be easily transferred from the rectum to the vagina and the urethra.

Sexual Behavior. Frequent sexual activity increases the risk of urinary tract infection, and studies indicate that nearly 80 percent of all urinary tract infections occur within 24 hours of intercourse. Contraceptives may also contribute to risk in a number of ways:

• The spring-rim of the diaphragm may bruise the area near the bladder neck, making it susceptible to bacteria. 
• Unlubricated condoms may injure vaginal tissue and make it vulnerable to infections. (Using a sterile lubricant, such as KY jelly, may help reduce this risk. Petroleum-based lubricants should be avoided because they weaken latex condoms.) 
• Spermicides are not protective, and, in fact, greatly increase the risk for urinary tract infections. 
• Some women experience UTI as an allergic reaction to latex in condoms or to oral contraceptives.

Pregnancy. Although pregnancy does not increase the rates of asymptomatic UTIs, it does increase the risk that it will progress to a full-blown infection. About two to 11 percent of pregnant women have asymptomatic UTIs, and of those, 13 to 27 percent will develop kidney infection late in their term. (It should be noted, however, that in early pregnancy, frequent urination, a common symptom of UTI, is most likely due to pressure on the bladder.)

Although all pregnant women should be tested for UTIs, those at particularly high risk are those with the following conditions or situations: diabetes, sickle cell trait, members of low-income groups, women who have had many children, women who have a history of childhood UTIs, women who have or had a catheterization of the bladder, and women who have received epidural anesthesia.

Women who have had a UTI before or during pregnancy also have a higher risk of developing recurrent urinary tract infections after delivery. Approximately 25 to 33 percent of women who experience UTIs during pregnancy will have another, sometimes as long as ten to 14 years later.

The major groups of women who are at highest risk for recurrent infections are highly sexually active young women and postmenopausal women. It might be argued that nearly all women who have a urinary tract infection are at risk for another, particularly if they are not treated for the first one. Changes after menopause put older women at particular risk for primary and recurring UTIs. In fact, studies indicate that between 20 and 25 percent of women over 65 years old have UTIs.

THE URINARY SYSTEM AND ITS DEFENSES AGAINST BACTERIA

The Urinary System The urinary system is made up of several organs that help maintain proper water and salt balance throughout the body and also expel urine from the body. It is made up of the following organs and structures: The two kidneys, located on each side below the ribs and toward the middle-back, play the major role in this process. They filter waste products, water, and salts from the blood to form urine.  Urine passes from each kidney to the bladder through thin tubes called ureters.  Ureters empty into the bladder, which rests on top of the pelvic floor. This is a muscular structure similar to a sling running between the pubic bone in front to the base of the spine.  The bladder stores the urine, which is then eliminated from the body via another tube called the urethra, which is the lowest part of the urinary tract. (In men it is enclosed in the penis. In women it leads directly out.) Defense Systems Against Bacteria Infection does not always occur when bacteria are introduced into the bladder. A number of defense systems protect the urinary tract against infection-causing bacteria: Many bacteria are washed out with the urine flow associated with normal urination.  Urine itself functions as an antiseptic, washing potentially harmful bacteria out of the body. (Urine is normally sterile, that is, free of bacteria, viruses, and fungi.)  The movement of the ureters assures that urine will not back up into the kidneys but lfow naturally into the bladder.  The prostate gland in men secretes infection-fighting substances.  The immune systems itself in both sexes continuously fight bacteria and other harmful micro-invaders. In addition, the immune system defenses and antibacterial substances in the mucus lining of the bladder eliminate many organisms.  In normal fertile women, the vagina is colonized by lactobacilli, beneficial microorganisms that maintain a highly acidic environment (low pH). Acid is hostile to other bacteria. Lactobacilli also produce hydrogen peroxide, which helps eliminate bacteria and reduces the ability of E. coli to adhere to vaginal cells. (E. coli is the major bacterial culprit in urinary tract infections.)

Prevention

The following hygiene tips may be helpful for women at risk for UTIs:

• Urinate as soon as convenient following sex.
• Cleanse the genital and urinary areas from front to back with soap and water after each bowel movement. 
• Avoid tight-fitting pants. 
• Wear cotton-crotch underwear and panty hose, changing both at least once a day. (Mild detergents are best for washing underwear.) 
• Take showers rather than baths. 
• Avoid bath oils, feminine hygiene sprays, douches, and powders. In fact, as a general rule, any product containing perfumes or other possible allergens should not be used near the genital area. 
• Choose sanitary napkins instead of tampons (which some physicians believe encourage infection). Napkins and tampons, in any case, should be changed after each urination. 
• Urinate frequently.

The following recommendations may reduce the risks from sexual activity:

• Keep the genital and anal areas clean before and after sex. 
• Discuss the best contraceptive choice with a physician; this is for women who don't want to get pregnant and who also want to reduce the risk for UTIs. For example, women in a monogamous relationship (in which both partners are at low risk for sexually transmitted disease) should consider contraceptive devices that don't contain spermicides. Uncoated condoms do not pose a risk for recurrent UTIs, but the friction they produce in use may pose a risk for infection. Uncoated condoms are also not as protective against sexually transmitted diseases. 
• Avoid sex with multiple partners. This may lead to health problems, including sexually transmitted diseases and UTIs.

Symptoms

Symptoms of UTIs usually begin suddenly and may include one or more of the following symptoms: 

• The urge to urinate frequently, which may recur immediately after the bladder is emptied. 
• A painful burning sensation. (If the only symptom is a burning sensation, then the infection is most likely urethritis.) 
• Discomfort or pressure in the lower abdomen. The abdomen can feel bloated. 
• Cramping in the pelvic area or back. 
• The urine often has a strong smell, looks cloudy, or contains blood. This is a sign of pyuria, which means the presence of a high white blood cell count, and is a very reliable sign for urinary tract infections. 
• Occasionally, fever develops.

Diagnosis

A physical examination and an analysis of a urine sample are the standard initial tests both to diagnose urinary tract infections and rule out other conditions. These tests may not be necessary in women with symptoms associated with a recent increase in sexual activity.  If you have clear-cut UTI symptoms, including frequent urination and, in women, vaginal burning, without other complications, such as fever, chills, and pain in the kidney, check with your doctor.  These signs are usually associated with UTIs and can be treated by your physician.
 
Increasingly, a nurse rather than a physician is consulted for uncomplicated urinary tract infections. A good response to antibiotic therapy usually eliminates the need for further tests. Pregnant women should be screened for E. coli because of the risk of complications, including miscarriage, form certain strains of this bacterium.

If an exam is needed for a female patient, your doctor should examine the pelvic and vaginal area. Men require a digital rectal examination to determine if prostate enlargement is present. Your physician will also examine the male genitals for signs of infection. In both men and women, your physician should also check the abdomen and areas around the kidneys for swelling and tenderness.

Also as part of an exam, you'll need to urinate into a cup so your urine can be tested. In addition, your doctor may need to take pictures of your kidneys with an x-ray or ultrasound and look into your bladder with an instrument called a cystoscope.

Urine tests. Your urine will be checked under a microscope for bacteria and infection-fighting cells and your doctor may order a urine culture. In this test, bacteria from the urine are allowed to grow in a lab dish so the exact type of bacteria can be seen and the precise type of medicine you need can be chosen.

Images. Your doctor may use either x-rays, sound waves (ultrasound), or CT scan to view your bladder or kidneys. These pictures can show stones, blockage, or swelling.

Cystoscopy. The urethra and bladder can be seen from the inside with a cystoscope, which is a thin tube with lenses like a microscope. The tube is inserted into the urinary tract through the urethra.

Treatment Options

Curative antibiotics may take several hours before they eliminate your symptoms.  The sooner you see your physician, the sooner the relief of your symptoms will occur. 

A variety of antibiotics are available for UTIs. The choices depend on many factors, including whether the infection is complicated or uncomplicated, primary or recurrent.

Fluoroquinolones. Antibiotics known as fluoroquinolones (also called quinolones) are becoming the standard therapy for UTIs.  Examples of quinolones include ciprofloxacin (Cipro), norfloxacin (Noroxin), levofloxacin (Levaquin), and sparfloxacin. These antibiotics are expensive.  Pregnant women should not take them. 

TMP-SMX. The combination drug trimethoprim-sulfamethoxazole, commonly called TMP-SMX (Bactrim, Cotrim, Septra), has been the standard therapy for UTIs but bacterial resistance to this treatment has been increasing. It should not be used in patients whose infections occurred after dental work or in patients allergic to sulfa drugs. Allergic reactions can be very serious. TMP-SMX also interferes with the effectiveness of oral contraceptives. Trimethoprin (Proloprim, Trimpex) or sulfamethoxazole (Thiosulfil, Forte) may be used alone or in combination.

Amoxicillin. Until recent years, the standard treatment for a UTI was ten days of amoxicillin, a penicillin antibiotic. This is the drug of choice for a certain bacterium (entrococcus).

All of the above antibiotic treatments are typically given in a three-day course.

Cephalosporins. Antibiotics known as cephalosporins, either second generation (cefuroxime axetil, cefaclor, cefprozil) or third generation (cefixime, cefotaxime, cefpodoxime) are also alternatives for infections that do not respond to standard treatments.

Tetracyclines. Long-term treatment with tetracycline or doxycycline (both are tetracyclines) may be used for infections that are caused by Mycoplasma or Chlamydia. Tetracyclines have unique side effects among antibiotics, including skin reactions to sunlight, possible burning in the throat, and tooth discoloration.

Nitrofurantoin. Nitrofurantoin (Furadantin, Macrodantin) is an antibiotic that is used specifically for urinary tract infections. It should not be used in patients with kidney disease. It interacts with many drugs and other chronic or serious medical conditions may also affect its use. It should not be used in pregnant women within a week or two of delivery or in nursing mothers.

A relapsing infection (caused by the same organisms the first episode) occurs within three weeks in about 10 percent of women. Relapse is treated similarly to a first infection but the antibiotics are continued for at least two weeks. Relapsing infections may be due to structural abnormalities, abscesses, or other problems that may require surgery, and such conditions should ordinarily be ruled out by a referral to a urologist.

Prophylaxis (preventive antibiotics) are an option for women who experience two or more new symptomatic UTIs within six months or three or more over the course of year (due to different organisms). A woman's own perception of discomfort should guide her decisions on whether to use preventive antibiotics or not. The increasing use of antibiotics for many common infections is causing concern because of emerging strains of common bacteria that have become resistant to standard antibiotics.

Last Updated: October 4, 2002
References:
Well-Connected
National Kidney and Urologic
Diseases Information Clearinghouse