INTRODUCTION — Urinary tract infection (UTI) is one of the most common infections. Approximately 50 percent of adult women report that they have had a UTI at some time during their life.
A UTI can be an infection of the bladder (cystitis) or a more serious infection of the kidney (pyelonephritis); most patients with UTI have an uncomplicated bladder infection that is easily treated with a short course of antibiotics.
This discussion will focus on bladder infections in a healthy adult.
DEFINITION — The urinary tract includes the kidneys (which filter urine), bladder (which stores urine), and urethra (the tube that carries urine out of the bladder) (show figure 1). Bacteria do not normally live in these areas. When bacteria enter the urinary tract and begin to multiply, they can cause a UTI. The majority of UTIs occur in the bladder.
UTI occurs more frequently in women since women have a short urethra and a small distance between the urethral opening and the anus (where bacteria commonly live, show figure 2). Both factors make it easy for bacteria to enter the bladder.
Most UTIs are caused by the bacterium Escherichia coli (E. coli), which is commonly found in feces. The bacteria can move from the anus to the urethra and into the bladder (and less commonly into the kidney), causing infection. E. coli have certain properties that enable this movement, including the ability to adhere to the lining of the urethra and bladder.
A patient who does not have symptoms but has bacteria in the urine is said to have asymptomatic bacteriuria. This is especially common in elderly men and women. Treatment is not always needed for persons with asymptomatic bacteriuria, except in selected circumstances, such as during pregnancy.
RISK FACTORS — The risk of developing cystitis or pyelonephritis may be increased by a number of factors, especially sexual intercourse. The use of spermicides, particularly in combination with a diaphragm, also increases the risk of UTI in women.
Some women are prone to recurring episodes of cystitis. Factors that may predispose a young woman to repeated episodes of cystitis include: Sexual activity Use of spermicides Genetic factors A new sex partner A history of previous UTIs is a very strong risk factor for having subsequent UTIs.
A small number of otherwise healthy young men can also develop UTI. Men who engage in insertive anal intercourse are more likely to become infected, as are men who are uncircumcised.
Men, women, and children with underlying health problems may also be at higher risk for developing a UTI, including use of a bladder catheter, a recent procedure or surgery involving the urinary tract, an anatomic abnormality or blockage of the urinary tract, the inability to empty the bladder completely, pregnancy, diabetes, or age 65 years.
SYMPTOMS — The typical symptoms of acute cystitis are: Pain or burning when urinating Frequent need to urinate Urgent need to urinate Blood in the urine Discomfort in the middle of the lower abdomen (suprapubic pain)
Burning with urination can also occur in patients with vaginitis (eg, yeast infection) or urethritis (inflammation of the urethra). The presence of blood in the urine is common in cystitis, but not in vaginitis or urethritis. Vaginal discharge, odor, itching, or pain with sexual intercourse are typical features of vaginitis. Urethritis is possible if the patient has a new sexual partner, has a partner with urethritis, or gradually develops symptoms over several weeks. (See "Patient information: Vaginal yeast infection" and see "Patient information: Blood in the urine (hematuria)").
Pyelonephritis — Symptoms of pyelonephritis (an infection of the kidney) almost always include fever, which is defined in adults as a temperature greater than 100.4º F (38º C). Pyelonephritis can also cause pain in the flank (side of lower back) on the involved side, nausea, and vomiting. Burning or pain on urination, frequent urination, urgency, and suprapubic pain may also occur in people with pyelonephritis.
DIAGNOSIS — Simple cystitis is usually diagnosed based upon symptoms alone. This is especially true if a woman has frequent UTIs and can recognize the symptoms easily. However, most patients, especially those with a first episode, should see a healthcare provider for testing.
The provider will examine the patient and look for fever or flank tenderness, which could indicate pyelonephritis. If vaginitis or urethritis are possible, a pelvic examination and appropriate cultures will be performed.
One way to distinguish between UTI and vaginitis is by performing a urinalysis to determine if there are white blood cells present. The urine will contain white blood cells in a person with a UTI, but these cells are not usually present in persons with vaginitis (although white blood cells in vaginal fluid can sometimes contaminate the urine specimen).
Urine culture — A urine culture is a test that uses a sample of urine to try and grow bacteria in a laboratory. A sensitivity test can be done with any bacteria that grow on the culture to determine the best antibiotic treatment. It usually requires about 48 hours for results to return.
Urine culture is done by obtaining a "clean catch" urine sample. The patient is asked to clean the external genitalia and collect a sample of urine after voiding for a few seconds. This avoids collecting the first drops of urine, which may be contaminated with bacteria from the skin.
However, a urine culture is not always required to diagnose a UTI. As noted above, it is often possible to accurately diagnose a UTI based on symptoms alone. Urine culture is helpful in patients who have symptoms that are not typical for UTI. Culture is also useful in patients who are at greater risk for having a bacteria that is resistant to antibiotics, such as a person who has recently taken antibiotics. In such cases, the information from the laboratory can be helpful in choosing the optimal antibiotic for the UTI.
TREATMENT — In young, healthy women with simple cystitis, the usual treatment includes several days of antibiotics. The typical drugs chosen are: trimethoprim-sulfamethoxazole (Bactrim®), nitrofurantoin (Macrobid®), ciprofloxacin (Cipro®) or levofloxacin (Levaquin®). Ciprofloxacin and levofloxacin should not be used by women who are pregnant or nursing. Symptoms generally resolve one to three days after starting treatment. It is important to take the full course of antibiotics to completely eliminate the infection.
If needed, medicine that numbs the bladder and urethra can be given for symptoms of painful urination (phenazopyridine [Pyridium®]). A nonprescription medication that is similar to Pyridium is also available (eg, Uristat). Both medications cause the urine to appear discolored (usually blue or orange) and can interfere with laboratory testing; for this reason, it is important to seek testing and treatment first.
Some providers recommend increasing fluid intake to help flush bacteria from the bladder. Others believe that increasing fluid in the body dilutes the antibiotic in the bladder and makes the medication less effective. No studies have been performed to address this issue. There are also no definitive studies on the effectiveness of cranberry juice for the treatment of a UTI.
Treatment in pregnancy — Pregnant women with a UTI or asymptomatic bacteriuria (a UTI without symptoms) need to be treated. Pregnant women are more likely to develop pyelonephritis following a UTI or asymptomatic bacteriuria, and UTIs can cause complications with the pregnancy. In pregnant women, the urine is sent for culture to identify the specific bacteria causing the problem, and the treatment is given for three to seven days.
Follow-up care — Follow-up testing is not needed in healthy, young women with simple cystitis if symptoms resolve. Pregnant women are usually asked to have a repeat urine culture two weeks after treatment has ended.
PREVENTING RECURRENT INFECTIONS — Young women with recurring urinary tract infections may be advised to take steps to prevent UTIs, including one or more of the following:
Changes in contraception — Women who use spermicides, particularly those who also use a contraceptive diaphragm, may be encouraged to use an alternate means of contraception UTIs frequently. (See "Patient information: Contraception").
Cranberry products — Several small studies have suggested that there may be some benefit to consuming cranberry products to prevent recurrent UTIs, but their effectiveness has not been proven. In the laboratory, cranberry extracts appear to decrease the ability of E. coli to stick to the cells lining the urinary tract. More definitive studies are needed before cranberry juice or supplements are recommended for this purpose.
Increasing fluid intake and urinating after intercourse — Although clinical studies have not proven that increasing fluid intake (for a total of 32 to 64 ounces of fluid per day from food or fluids) or urinating soon after intercourse can prevent infection, healthcare providers frequently recommend these measures since they are not harmful.
Postmenopausal women — Postmenopausal women who develop recurrent UTIs may benefit from use of a vaginal estrogen. Estrogen is thought to promote the growth of normal bacteria in the vagina while preventing the growth of harmful bacteria. Vaginal estrogen is available in a flexible ring that is worn in the vagina for three months (eg, Estring®), a small tablet (Vagifem®), or a cream (eg, Premarin® or Estrace®).
Antibiotics — A preventive antibiotic treatment should be considered for people who continue to develop UTIs despite use of other preventive measures. Antibiotics are highly effective in preventing recurrent UTIs and can be given in several different ways.
Continuous use of antibiotics — A low dose of an antibiotic may be taken daily or three times per week for six months to several years.
Antibiotics following intercourse — In women who develop urinary tract infections after sexual intercourse, a single low dose antibiotic after intercourse is often effective in preventing infection.
Self-treatment — A plan to begin antibiotics at the first sign of a UTI may be recommended for some. Before this is started, it is important that prior infections have been confirmed with a urine culture; some women have symptoms of a UTI but do not actually have an infection. (See "Patient information: Chronic pelvic pain in women", section on Painful bladder syndrome and interstitial cystitis).
Need for further testing — Young healthy women with UTI who respond to antibiotic therapy, even those with pyelonephritis or frequent bladder infections, rarely need to undergo further testing. However, further testing may be recommended for some people with recurrent urinary tract infections, especially if there is any possibility of an anatomic abnormality in the kidneys, ureter, bladder, or urethra, or if there is concern about other factors that increase the risk of a urinary tract infection (eg, kidney stone). In addition, anyone who continues to have blood in the urine after the infection has cleared should be evaluated. (See "Patient information: Kidney stones" and see "Patient information: Blood in the urine (hematuria)").
Further evaluation of the urinary tract may include a computed tomography (CT) scan, ultrasound, or cystoscopy (looking inside the bladder with a thin, lighted telescope-like instrument).
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
Centers for Disease Control and Prevention (CDC)
Toll-free: (800) 311-3435
(www.cdc.gov)
Infectious Diseases Society of America
(www.idsociety.org)
National Kidney and Urologic Disease Information Clearinghouse
(http://kidney.niddk.nih.gov/kudiseases/pubs/utiadult/)
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2. Hooton, TM, Besser, R, Foxman, B, et al. Acute uncomplicated cystitis in an era of increasing antibiotic resistance: a proposed approach to empirical therapy. Clin Infect Dis 2004; 39:75.
3. Hooton, TM, Stamm, WE. Diagnosis and treatment of uncomplicated urinary tract infection. Infect Dis Clin North Am 1997; 11:551.
4. Scholes, D, Hooton, TM, Roberts, PL, et al. Risk factors associated with acute pyelonephritis in healthy women. Ann Intern Med 2005; 142:20.
5. Hooton, TM. The current management strategies for community-acquired urinary tract infection. Infect Dis Clin North Am 2003; 17:303.
6. Raz, R, Chazan, B, Dan, M. Cranberry juice and urinary tract infection. Clin Infect Dis 2004; 38:1413.
7. Stamm, WE. Estrogens and urinary-tract infection. J Infect Dis 2007; 195:623.
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