How Do UTIs Begin?

Many types of bacteria live in the intestines and the genital area, but this is not true of the urinary system. In fact, urine is sterile. So when errant bacteria, such as the E. coli shown here, is accidentally introduced into the urinary system, it can start a UTI. Typically, bacteria travel up the urethra to the bladder, where an infection can take hold. Women are more susceptible than men, probably because they have shorter urethras.