Urinary tract infections are caused by a variety of factors, which are related to the virulence of pathogenic bacteria and human resistance. The common causes are: first, factors existing in the urinary tract itself: such as the presence of stones, foreign bodies, tumors or after various medical operations, such as indwelling catheters or indwelling ureter or stent tubes, resulting in a decrease in the defense capacity of the bladder and urethra mucosa, which is conducive to the colonization and invasion of bacteria; second, urinary tract obstruction: the presence of symptoms of obstruction for different reasons, such as urethral obstruction caused by the prostate or obstruction of the ureter and bladder caused by stones and tumors, resulting in incomplete emptying of urine and retention in the body, which in turn causes bacterial infection; third, neurological damage: extensive surgery, such as pelvic and gynecological, leads to extensive damage to the muscles governing the urinary tract and the nervous system of the voiding function, causing difficulty in urination and subsequently infection. Of course, it is also related to the body’s resistance. In a normal state of immunity, there is a certain defense against bacterial infections, but when various pathogenic factors lead to a decrease in immunity, bacteria are more likely to colonize the urinary tract and urinary tract infections occur.