A urinary tract infection (UTI) is an infection in any part of your urinary system—your kidneys, ureters, bladder, and urethra. Most infections involve the lower urinary tract — the bladder and the urethra. Your urinary tract is how your body gets rid of things it cannot use in the bloodstream, such as salts, toxins, and excess water. Your kidneys filter out these substances and convert them to urine. The urine travels down to your bladder through a pair of narrow tubes known as ureters. The urine then waits in your bladder until you’re ready to urinate. When you go to the bathroom, the urine leaves your bladder through a tube called the urethra and exits your body through the tip of your penis if you’re male, or just above the vaginal opening if you’re female.
You might think, that handling all that waste material, your urinary tract would be filled with germs—but your body’s natural defenses flush most bacteria out of your urinary tract before they cause any problems. However, there may be times when bacteria, viruses, or fungi can overwhelm your body’s normal defenses and cause a urinary tract infection (UTI).
UTIs can happen to anyone, but they are 4 times more common in women than in men. More than half of all women will have a UTI at some point in their lives. About 1 in 5 women who have UTIs when they are young will go on to have recurrent infections throughout their lives. UTIs in men are less common, but can be harder to treat when they do occur, and often lead to recurrent infections.
Most urinary tract infections occur in the bladder or the urethra. An infection in the bladder is known as cystitis. An infection of the urethra is urethritis. Sometimes a urinary tract infection can travel up the ureters and cause a kidney infection. This is known as pyelonephritis. Pyelonephritis is less common than other urinary tract infections, but it can be much more serious. It’s important to treat a urinary infection before it reaches your kidneys. But pyelonephritis can usually be treated successfully if it’s caught early.