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Understanding Urinary Tract Infections (UTIs)

Most UTIs are caused by bacteria, although they may also be caused by viruses or fungi. Bacteria from the bowel are the most common source of infection. The infection may begin because of any of the following:

  • Sexual activity. During sex, germs can travel from the penis, vagina, or rectum into the urethra. 

  • Germs on the skin outside the rectum may travel into the urethra. This is more common in women since the rectum and urethra are closer to each other than in men. Wiping from front to back after using the toilet and keeping the area clean can help prevent germs from getting to the urethra.

  • Blockage of urine flow through the urinary tract. If urine sits too long, germs may begin to grow out of control.

An image of the woman's urinary tract system showing the ureter connects the kidney to the bladder. The urethra is the tube that carries urine out of the body. The vagina and rectum are also identified.

Image of a man's urinary tract system showing the ureter connecting the kidney to the bladder and the urethra leading out of the penis. the rectum and prostate are identified.

Parts of the urinary tract

The infection can occur in any part of the urinary tract.

  • The kidneys collect and store urine.

  • The ureters carry urine from the kidneys to the bladder.

  • The bladder holds urine until you are ready to let it out.

  • The urethra carries urine from the bladder out of the body. It is shorter in women, so bacteria can move through it more easily. The urethra is longer in men, so a UTI is less likely to reach the bladder or kidneys in men.

© 2000-2015 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.