basics of urinary tract infection

Urinary tract infections result in nearly 10 million office visits, 1.5 million hospitalizations and $1 billion in health care costs, according to the National Kidney Foundation. Two-thirds of office visits are by women of childbearing age.
One in every five women will have at least one urinary tract infection in her life, and some women will have more. Luckily, most infections are not serious and can be easily treated with antibiotic medications. But a urinary tract infection can be stubborn, and sometimes recurs a few weeks after treatment. Nearly 20 percent of women who have a urinary tract infection will have another, and 30 percent of those who have had two will have a third. About 80 percent of those who have had three will have a fourth. If left untreated, urinary tract infections can lead to other more complicated health problems, so they should not be ignored.
Your urinary tract includes two kidneys, two ureters, the bladder and the urethra. Your kidneys remove waste and water from your blood to produce urine. Urine travels through muscular tubes, called the ureters, to the bladder. The bladder is a balloon-like organ composed of muscle, connective tissue and nerves that swells as it fills with urine. Urine is stored in the bladder until it is released from the body through another tube, called the urethra. Two muscle groups, the pelvic floor muscles and the urinary sphincters, control the activity of the urethra and bladder neck. These muscles must work together to hold urine in the bladder most of the time and allow the bladder to empty when appropriate.
Most urinary tract infections are caused by a variety of bacteria, including Escherichia coli (E. coli), found in feces. In younger women staph saphrophyticus is the most common organism causing UTIs. Because the openings of the bowel, vagina and urethra are very close together, it's easy for the bacteria to spread to the urethra and travel up the urinary tract into the bladder, and sometimes up to the kidneys.
Infection occurs when the bacteria cling to the opening of the urethra and multiply, producing an infection of the urethra, called urethritis. The bacteria often spread up to the bladder, causing a bladder infection. If the problem is not treated, the infection can continue spreading up the urinary tract, causing infection in the kidneys, called pyelonephritis. A kidney infection that is not treated can result in the bacteria entering the bloodstream (this is known as urosepsis), which can be a life-threatening infection requiring hospitalization and intravenous antibiotics.