A urinary tract infection (UTI) is an infection in any part of your urinary system including your kidneys, ureters, bladder, and urethra (the structures through which urine passes before being expelled from the body). Most infections involve the lower urinary tract (the bladder and the urethra). The further up in the urinary tract an infection occurs, the more serious the infection is.
UTIs usually occur when bacteria enter the urinary tract through the urethra and begin to multiply. When that happens, bacteria may take hold and grow into a full-blown infection in the urinary tract.
Urinary tract infections don't always produce symptoms, but when they do they may include: