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Causes
By Mayo Clinic staffUrinary 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, these defenses sometimes fail. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.
The most common UTIs occur mainly in women and affect the bladder and urethra.
- Infection of the bladder (cystitis). This type of UTI is usually caused by Escherichia coli (E. coli), a type of bacteria commonly found in the gastrointestinal (GI) tract. Sexual intercourse may lead to cystitis, but you don't have to be sexually active to develop it. All women are at risk of cystitis because of their anatomy — specifically, the short distance from the urethra to the anus and the urethral opening to the bladder.
- Infection of the urethra (urethritis). This type of UTI can occur when GI bacteria spread from the anus to the urethra. Also, because the female urethra is close to the vagina, sexually transmitted infections, such as herpes, gonorrhea and chlamydia, can cause urethritis.
References
- Wein AJ, et al. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.mdconsult.com/das/book/body/208746819-6/0/1445/0.html. Accessed July 19, 2012.
- Urinary tract infection in adults. National Kidney and Urologic Diseases Information Clearinghouse. http://kidney.niddk.nih.gov/KUDiseases/pubs/utiadult/index.aspx. Accessed July 19, 2012.
- Lentz GM, et al. Comprehensive Gynecology. 6th ed. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/linkTo?type=bookPage&isbn=978-0-323-06986-1&eid=4-u1.0-B978-0-323-06986-1..C2009-0-48752-X--TOP. Accessed July 19, 2012.
- Urinary tract infections in children. American Urological Association Foundation. http://www.urologyhealth.org/urology/index.cfm?article=46. Accessed July 19, 2012.
- McPherson RA, et al. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa.: Saunders Elsevier; 2011. http://www.mdconsult.com/das/book/body/208746819-6/0/1393/0.html. Accessed July 19, 2012.
- Hooton TM. Recurrent urinary tract infection in women. http://www.uptodate.com/index. Accessed July 19, 2012.
- Wang CH, et al. Cranberry-containing products for prevention of urinary tract infections in susceptible populations. Archives of Internal Medicine. 2012;172:988.
- Cranberry. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed July 19, 2012.
- Jepson RG, et al. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD001321.pub4/abstract. Accessed July 31, 2012.
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