We were told to wipe from front to back after using the toilet. Indeed, the urethra, the tube that carries urine from the bladder to the outside of the body, is located near the anus. Bacteria from the large intestine, such as E.coli, are in an ideal position to escape the anus and invade the urethra. From there, they can travel up to the bladder and, if the infection is left untreated, continue to infect the kidneys. Women may be particularly prone to UTIs because they have a shorter urethra, which allows bacteria to quickly access the bladder. Having sex can also introduce bacteria into the urinary tract.