A UTI develops when microbes (pronounced MAHY-krohbs) enter the urinary tract and cause infection. Bacteria are the most common cause of UTIs, although fungi rarely can also infect the urinary tract. E. coli bacteria, which live in the bowel, cause most UTIs.
The female anatomy contributes to women's increased likelihood of contracting a UTI.1 A woman's urethra is shorter than a man's, allowing bacteria better access to the bladder. A woman's urethral (pronounced yoo-REE-thruhl) opening is also close to sources of bacteria from the anus and vagina. Sexual activity can move bacteria to the urethral opening.
Having bacteria in the bladder does not always mean there is an infection. Like the bowel, the bladder has bacteria and other microorganisms that help to keep it healthy and functioning properly.
Some forms of birth control also increase the risk of UTIs. Spermicides can cause skin irritations that allow bacteria to invade. Diaphragms may slow urinary flow, encouraging bacteria to multiply. Unlubricated condoms or spermicidal condoms may cause irritation, which can help bacteria grow.1
The following factors also may encourage bacteria to grow:1
For information about UTIs in children, visit http://kidney.niddk.nih.gov/KUDiseases/pubs/utichildren/index.aspx.
UI is caused by problems with the muscles and nerves that hold or release urine. These muscles include bladder muscles, which contract to force urine into the urethra, and sphincter muscles that surround the urethra, which relax to allow urine to pass from the body. Incontinence occurs if bladder muscles suddenly contract or sphincter muscles are not strong enough to hold back urine.
These muscles also help to hold the urinary tract in place, so if the muscles are weakened, they may not be able to keep the bladder or other structures in the right position in the body. These types of structural problems, such as when the bladder is out of position, can also cause UI.
UTIs, vaginal infections or irritation, and medications can temporarily cause or aggravate UI. Constipation and being overweight or obese put pressure on the bladder and its controlling muscles and can also cause or aggravate UI.
Other features and conditions that can contribute to UI in women include:2
For information about UI in men, visit http://kidney.niddk.nih.gov/KUDiseases/pubs/uimen/index.aspx.
For information about UI in children, visit http://kidney.niddk.nih.gov/KUDiseases/pubs/uichildren/index.aspx.
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