Urinary tract infections (UTIs) account for about eight million visits to physicians each year in the United States. These infections are much more common in adults, particularly in women. Children account for one to two percent of all UTIs, but their infections are often more serious. About 40 percent of women and 12 percent of men have a UTI at some time in their life.

The urinary system or "tract" is composed of the kidneys, ureters, bladder and urethra. The kidneys produce urine that passes down the ureters to the bladder, where it is stored, before passing out the urethra. An infection can involve one or more parts of the urinary system.

Most UTIs are caused by bacteria that normally inhabit the bowel and live around the anus. The bacterium Escherichia coli (E. coli) is far and away the most common offender. Bacteria cause UTIs by making their way to the opening of the urethra where they can enter and start to grow anywhere in the urinary tract.

The two most common ways bacteria enter the urinary tract in women is through improper hygiene (wiping from back to front after a bowel movement), and sexual intercourse. Older men are also more prone to UTIs because their bladders may not empty completely due to enlargement of the prostate gland.

If the urethra is the only part of the urinary tract involved, the condition is called urethritis. This can be caused by colon bacteria, but may also be caused by sexually transmitted organisms. The infection can progress up the urinary tract causing infection of the bladder (cystitis) or one or both kidneys (pyelonephritis).

Urinary tract infections can be simple or complicated. Most are simple, responding rapidly to antibiotics. Complicated UTIs are caused by bacteria that are resistant to antibiotics, or that have become too numerous to treat effectively. Children may develop complicated infections because of anatomic abnormalities in their urinary tracts. As a general rule, the farther up the urinary tract an infection is, the more severe the infection.

UTI symptoms vary based on the location of the infection. Urethritis usually results in burning with urination (dysuria). This is usually described as "external" burning (i.e. not up in the pelvis). Cystitis irritates the wall of the bladder and results in frequent urination and possibly pelvic pain and cramping. It may also cause blood in the urine (hematuria). Children may present with fever, abdominal pain, vomiting, foul-smelling urine or loss of bladder control.

If the infection progresses up the ureters to the kidneys, it can cause back or flank pain as the kidney(s) become inflamed. This usually results in high fever, nausea and vomiting. Pyelonephritis, particularly in children, can lead to scarring of the kidneys and put the kids at increased risk of developing high blood pressure later in life.

Most UTIs can be treated effectively with oral antibiotics. Simple UTIs usually respond to a three to five day course of medication. Many bacteria are becoming resistant to antibiotics like sulfa (often due to inappropriate overprescribing of antibiotics), so another antibiotic may be needed.

For women who develop UTIs following sexual intercourse, it is helpful to urinate shortly after sex. Treatment with a single dose of a "post-coital" antibiotic is also a common way to combat this problem.

People who have UTIs that are either recurrent or unresponsive to treatment should have their urine sent to the lab to be tested (a culture and sensitivity) to see what antibiotics will kill bacteria causing the infection. Since UTIs are less common in younger men, it is usually recommended that they have cultures done as well.

Children under age five who develop UTIs should be evaluated carefully with possible imaging of their urinary systems to look for anatomic abnormalities. If they have had pyelonephritis, they should also have their blood pressure checked on a regular basis.

And no, recent scientific studies indicate that cranberry juice is not effective in preventing or treating UTIs.

Dr. John Roberts is a family physician. He is also one of the owners of The Paper of Montgomery County. Send him your question today by e-mail at thedoctor@thepaper24-7.com.