A bladder infection or Urinary Tract Infection (UTI) is a bacterial infection that affects any part of the urinary tract. When bacteria get into the bladder and multiply in the urine, it causes a UTI.
The most common type of UTI is a bladder infection, which is also often called cystitis. Cystitis literally means an inflammation of the bladder. The other kind of UTI is a kidney infection, which is also known as pyelonephritis. This kind of infection can be serious, but if treated quickly, the kidney is not usually damaged permanently.