Urinary Tract Infection

organs of the renal system

urinary tract infection (UTI), in humans, inflammation of the renal system characterized by frequent and painful urination and caused by the invasion of microorganisms, usually bacteria, into the urethra and bladder. Infection of the urinary tract can result in either minor or major illness. For example, an attack of cystitis—inflammation of the bladder—may cause only a small amount of pain and discomfort, whereas infection that spreads into the upper urinary tract may lead to acute complications, such as obstruction of the ureter and kidney failure, or to chronic conditions, such as incontinence or kidney scarring that gradually progresses to kidney failure. Severe or recurrent UTI can result in lifelong discomfort and decrease in quality of life.