What causes urinary tract infections (UTIs)?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner
Bacteria, a type of germ that gets into your urinary tract, cause a UTI. This can happen in many ways:
  • Wiping from back to front after a bowel movement (BM). Germs can get into your urethra, which has its opening in front of the vagina.
  • Having sexual intercourse. Germs in the vagina can be pushed into the urethra.
  • Waiting too long to pass urine. When urine stays in the bladder for a long time, more germs are made, and the worse a UTI can become.
  • Using a diaphragm for birth control, or spermicides (creams that kill sperm) with a diaphragm or on a condom Anything that makes it hard to completely empty your bladder, like a kidney stone.
  • Having diabetes, which makes it harder for your body to fight other health problems.
  • Loss of estrogen (a hormone) and changes in the vagina after menopause. Menopause is when you stop getting your period.
  • Having had a catheter in place. A catheter is a thin tube put through the urethra into the bladder. It's used to drain urine during a medical test and for people who cannot pass urine on their own.

This answer is based on source information from the National Women's Health Information.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Urinary tract infections are a common ailment that affect women more often than men. Learn how to prevent them as Dr. Oz discusses the bladder and tips to ward off infections in this video.
Kevin W. Windom, MD
OBGYN (Obstetrics & Gynecology)
Urinary tract infections are caused by bacteria that occur in fecal material. This is the reason why women are told to wipe from "front to back". The most common bacteria seen in a urinary tract infection is E. coli, and this is also commonly seen in feces. Urinary tract infections can be caused by sexual intercourse, waiting too long to urinate, inadequate bladder emptying, and some forms of birth control such as spermicidal jelly and the use of diaphragms.  There are medical problems that can increase the risk of urinary tract infections, and the most common is diabetes. Diabetic patients can have inadequate bladder emptying and chronically have high residual volumes of urine in their bladder.  Lastly, women who go through menopause and have a lack of estrogen in the vaginal tissue can have an increased risk of bladder infections. The reason is that there are numerous estrogen receptors in the vagina, and a lack of estrogen can cause the vaginal tissue to become atrophic or dry, and this can cause the increase in bacteria from the rectum to flourish in the vagina and then it is very easy for the bacteria to go from the vagina to the urethra causing a bladder infection.
Michael T. Murray, ND
Naturopathic Medicine

Most urinary tract infections are caused by the E. coli bacterium. Many factors are associated with increased risk of urinary tract infections (UTI): pregnancy (twice as frequent); menopause; sexual intercourse (nuns have one tenth the incidence); mechanical trauma or irritation; and, perhaps most important, structural abnormalities of the urinary tract that block the free flow of urine, such as benign prostatic hyperplasia in men.

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Dr. Robin Miller, MD
Internal Medicine

Women who are sexually active are susceptible to urinary tract infection (UTI). Women have a short urethra (the tube between the bladder that allows flow of urine out of the body). This makes it easier for skin and fecal bacteria to make their way up into the bladder especially with sexual activity. 

Those who use a diaphragm, spermicide foam, or have partners who use condoms for birth control also are at increased risk of infection.

As women age, the urinary tract thins and this too can increase the chance of infection. In addition, loss of estrogen reduces the ability of the vagina to block bacteria from entering. Finally, women with skin allergies are at increased risk for UTI.

Dr. Michael Roizen, MD
Internal Medicine
Urinary tract infections (UTIs) are triggered by bacteria (and sometimes fungi and viruses). The old thinking was this: bugs enter the urethra (the tube that urine goes through) and colonize the bladder and kidney after sex or—for women—if you wipe wrong. It's true that those things can trigger UTIs, but both good and bacteria live in your bladder all the time. We don't really know what's going on in there, so the real remedy is prevention.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.