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Urinary tract infection (UTI) is a common infection that usually occurs when bacteria enter the opening of the urethra and multiply in the urinary tract. The urinary tract includes the kidneys, ureters (tubes that carry urine from the kidneys to the bladder), bladder, and urethra (tube that carries urine from the bladder). The special connection of the ureters at the bladder help prevent urine from backing up into the kidneys, and the flow of urine through the urethra helps to eliminate bacteria. Men, women, and children develop UTIs.

Types
Urinary tract infections usually develop first in the lower urinary tract (urethra, bladder) and, if not treated, progress to the upper urinary tract (ureters, kidneys). Bladder infection (cystitis) is by far the most common UTI. Infection of the urethra is called urethritis. Kidney infection (pyelonephritis) requires urgent treatment and can lead to reduced kidney function and possibly even death in untreated, severe cases.

Incidence and Prevalence
Approximately 8 to 10 million people in the United States develop a UTI each year. Women develop the condition much more often than men, for reasons that are not fully known, although the much shorter female urethra is suspected. The condition is rare in boys and young men.

Twenty percent of women in the United States develop a UTI and 20% of those have a recurrence. Urinary tract infections in children are more common in those under the age of 2.

Causes and Risk Factors

Escherichia coli (E. coli) causes about 80% of UTIs in adults. These bacteria are normally present in the colon and may enter the urethral opening from the skin around the anus and genitals. Women may be more susceptible to UTI because their urethral opening is near the source of bacteria (e.g., anus, vagina) and their urethra is shorter, providing bacteria easier access to the bladder. Other bacteria that cause urinary tract infections include Staphylococcus saprophyticus (5 to 15% of cases), Chlamydia trachomatis, and Mycoplasma hominis. Men and women infected with chlamydia trachomatis or mycoplasma hominis can transmit the bacteria to their partner during sexual intercourse, causing UTI.

Sexual intercourse triggers UTI in some women, for unknown reasons. Women who use a diaphragm develop infections more often, and condoms with spermicidal foam may cause the growth of E. coli in the vagina, which may enter the urethra.

Urinary catheterization (small tube inserted into the bladder through the urethra to drain urine) can also cause UTI by introducing bacteria into the urinary tract. The risk for developing a UTI increases when long-term catheterization is required.

In infants, bacteria from soiled diapers can enter the urethra and cause UTI. E. coli may also enter the urethral opening when young girls do not wipe from front to back after a bowel movement.

Other risk factors include the following:

• Bladder outlet obstructions (e.g., kidney stones, BPH)
• Conditions that cause incomplete bladder emptying (e.g., spinal cord injury)
• Congenital (present at birth) abnormalities of the urinary tract (e.g., vasicoureteral reflux)
• Suppressed immune system
• Being uncircumcised

Certain blood types enable bacteria to attach more easily to cells that line the urinary tract, causing recurrent UTIs.

Signs and Symptoms

Symptoms of UTI in young children include the following:

• Diarrhea
• Excessive crying that cannot be resolved by typical measures (e.g., feeding, holding)
• Loss of appetite
• Fever
• Nausea and vomiting

Older children may experience the following symptoms with UTI:

• Flank or lower back pain (with a kidney infection)
• Frequent urination
• Inability to produce more than a small amount of urine at a time
• Incontinence
• Pain in the abdomen or pelvic area
• Painful urination (dysuria)
• Urine that is cloudy or has an unusual smell

Symptoms of lower UTI (e.g., cystitis, urethritis) in adults include the following:

• Back pain
• Blood in the urine (hematuria)
• Cloudy urine
• Inability to urinate despite the urge
• Fever
• Frequent need to urinate
• Painful urination (dysuria)
• Malaise (general discomfort)

Symptoms that indicate upper UTI (e.g., pyelonephritis) in adults include the following:

• Chills
• High fever
• Nausea
• Pain below the ribs
• Vomiting

Complications

Hormonal changes and shifts in the urinary tract during pregnancy increase the risk for kidney infection. Prenatal care includes regular urine testing because bacteria are often present without causing symptoms and UTI during pregnancy may result in complications (e.g., premature birth, high blood pressure) for the mother and fetus. Diseases that suppress the immune system (e.g., HIV) and debilitating diseases (e.g., cancer, sickle cell anemia) increase the risk for UTIs and complications.

Diagnosis

A clean-catch urine specimen is obtained to diagnose UTI. This test involves cleansing the area around the urethral opening and collecting a mid-stream urine sample, preventing bacteria in the genital area from contaminating the sample. Urinalysis is performed to determine the level of leukocytes (white blood cells that destroy harmful bacteria) in the urine. A large number of these cells may indicate bacterial infection. A culture and sensitivity (induced growth of the bacteria) may be done to determine the type of bacteria and how to treat the infection.

Treatment

UTIs are treated with antibacterial drugs. The type of drug used and the duration of treatment depend on the type of bacteria. Most UTIs are treated with trimethoprim-sulfamethoxazole (e.g., Bactrim®, Cotrim®, Septra®), amoxicillin (e.g., Amoxil®, Trimox®), or fluoroquinolones (e.g., Levaquin®, Cipro®). The infection may improve within a couple of days, but 1 to 2 weeks of medication is may be prescribed to prevent a kidney infection.

UTIs that are caused by bacteria such as chlamydia trachomatis and mycoplasma hominis require a longer course of treatment with tetracycline (e.g., Achromycin®), trimethoprim-sulfamethoxazole, or doxycycline (e.g., Periostat®).

Infections complicated by bladder outlet obstructions (e.g., kidney stone, BPH) and other risk factors (e.g., spinal cord injury) may require surgery to correct the cause of UTI. Kidney infections may require hospitalization and as many as 6 weeks of antibiotic treatment to prevent serious kidney damage.

Over-the-counter pain relievers (e.g., Tylenol®, Advil®) and a heating pad may be used to relieve discomfort caused by UTI. Drinking plenty of water helps to cleanse bacteria out of the urinary tract. Coffee, alcohol, and smoking should be avoided.

Frequent UTI (3 or more per year) may be treated with low-dose antibiotics for 6 months or longer or with a 1 to 2 day course when symptoms appear.

Follow up urinalysis is performed after treatment to make sure that the urinary tract is bacteria free.

Prevention

The following measures can reduce the risk for UTI:

• Avoid products that may irritate the urethra (e.g., bubble bath, scented feminine products).
• Cleanse the genital area before sexual intercourse.
• Change soiled diapers in infants and toddlers promptly.
• Drink plenty of water to remove bacteria from the urinary tract.
• Do not routinely resist the urge to urinate.
• Take showers instead of baths.
• Urinate after sexual intercourse.
• Women and girls should wipe from front to back after voiding to prevent contaminating the urethra with bacteria from the anal area.

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