Causes of Urinary Tract Infection

The vast majority of urinary tract infections in women are caused by bacteria entering the opening of the urethra and travelling up into the urinary bladder (cystitis) and the kidney (pyelonephritis). The most common bacteria involved, causing 90- 95% of UTIs, is Escherichia coli (E. coli).2 E. coli is a normal inhabitant of the colon (lower bowel), and, as such, is frequently found near the anal opening and the opening to the urethra. Women suffer more often than men from urinary tract infections because their urethras are shorter, making it easier for bacteria to reach the urinary bladder.

Most urinary tract infections in healthy, nonpregnant women are categorized as uncomplicated urinary tract infections. Complicated urinary tract infections occur in certain patient populations, including pregnant and diabetic women, and in people who have anatomic or functional abnormalities of their urinary tracts. This includes women with kidney stones, women with anatomical abnormalities of the kidneys present from birth, and women with bladder catheters.4