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Causes
By Mayo Clinic staffThe urinary system is composed of the kidneys, ureters, bladder and urethra. All play a role in removing waste from your body. Urinary tract infections typically occur when bacteria enter the urinary tract through the urethra and begin to multiply in the bladder. Although the urinary system is designed to keep out such microscopic invaders, the defenses sometimes fail. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.
The most common urinary tract infections occur mainly in women and affect the bladder and urethra.
- Infection of the bladder (cystitis) is usually caused by Escherichia coli (E. coli), a species of bacteria commonly found in the gastrointestinal tract. Sexual intercourse may lead to cystitis, but you don't have to be sexually active to develop it. All women are susceptible to cystitis because of their anatomy — specifically, the close proximity of the urethra to the anus and the short distance from the urethral opening to the bladder.
- Infection of the urethra (urethritis) can occur when gastrointestinal bacteria spread from the anus to the urethra. In addition, because of the female urethra's proximity to the vagina, sexually transmitted diseases (STDs), such as herpes, gonorrhea and chlamydia, also are possible causes of urethritis.
- Schaeffer AJ, et al. Infections of the urinary tract. In: Wein AJ, et al. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa.: Saunders; 2007. http://www.mdconsult.com/das/book/body/202281144-2/0/1445/0.html. Accessed May 21, 2010.
- Urinary tract infections in adults. National Institute of Diabetes and Digestive and Kidney Diseases. http://kidney.niddk.nih.gov/kudiseases/pubs/utiadult/index.htm. Accessed May 21, 2010.
- Lentz GM. Urogynecology: Physiology of micturition, diagnosis of voiding dysfunction, and incontinence: Surgical and nonsurgical treatment. In: Katz VL, et al. Comprehensive Gynecology. 5th ed. Philadelphia, Pa.: Mosby; 2007. http://www.mdconsult.com/das/book/body/202781245-2/0/1524/0.html. Accessed May 25, 2010.
- Urinary tract infections in children. UrologyHealth.org. http://www.urologyhealth.org/pediatric/index.cfm?cat=07&topic=146. Accessed May 25, 2010.
- McPherson RA, et al. Basic examination of urine. In: McPherson RA, et al. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/202781245-4/0/1393/0.html. Accessed May 25, 2010.
- Hooton TM. Recurrent urinary tract infection in women. http://www.uptodate.com/home/index.html. Accessed May 12, 2010.
- Guay DRP. Cranberry and urinary tract infections. Drugs. 2009;69:775.
- Cranberry. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed May 26, 2010.
- Jepson RG, et al. Cranberries for preventing urinary tract infections (review). Cochrane Database of Systematic Reviews. 2008;CD001321.
- Coumadin (prescribing information). Princeton, N.J.: Bristol-Myers Squibb; 2010. http://www.coumadin.com/for_hcp.aspx. Accessed May 26, 2010.
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