A urine sample showing dead white blood cells indicating UTI, courtesy Bobjgalindo, via Wikimedia Commons
A urinary tract infection or UTI describes any bacterial infection that affects the tract leading from the kidneys through the bladder and urethra, usually the result of E. coli working its way into the urinary tract, often through the urethra. They usually affect the bladder and are not serious, but those that affect the kidneys are potentially more serious and cause more serious symptoms. However, such infections react well to antibiotics as all antibiotics pass naturally in urine without losing their antiseptic effect.
Another urine sample, this time showing bacteria along with the white blood cells, courtesy Steven Fruitsmaak, via Wikipedia
UTIs are more common in women because their urethra is shorter and the exit is closer to the anus. Sexual intercourse is the most usual cause of infection, and in many cases a UTI can result after a woman's initial sexual encounter. Men are somewhat protected because their urethra is longer and the prostate can actually block bacteria. However, as the sexes age, the incidence of infection is similar in both sexes.
Patients who are on a urinary catheter are at risk for UTI.
Many individuals suffer from frequent or recurring UTIs. In such cases, a long term course of antibiotics is recommended, although cranberry juice also appears to be an effective way to prevent recurrent infections.