Cause urinary tract infection mainly consider the following reasons, such as urinary tract obstruction, gender and sexual life, pregnancy, medical treatment, urinary system structural abnormalities. 1. Urinary tract obstruction: various reasons lead to the urine can not be freely discharged, urethra bacteria is not easy to be flushed out, the local mass reproduction caused by infection, visible ureteral stones and stenosis, prostate hyperplasia, urinary tract tumors and so on. 2. Gender and sex life: female urethra is short and wide, close to the anus, when having sex, it is easy to squeeze the bacteria around the urethra and anus into the urethra and bladder to cause infection. The male circumcision is also the main reason for male urinary tract infections. 3. pregnancy: women’s ureteral peristalsis during pregnancy is weakened, as well as the uterus increases in size and presses the bladder and ureter, which may lead to poor urinary discharge, thus triggering urinary tract infections. 4. Medical treatment: such as catheterization, indwelling urinary catheter, cystoscopy and ureteroscopy, urinary tract surgery can cause urinary tract mucosal injury, bring bacteria into the urinary tract, causing urinary tract infection. 5. Abnormalities in the structure of the urinary system: such as renal hypoplasia, renal pelvis, ureteral malformation, polycystic kidneys, transplantation of kidneys, etc., which can easily reduce the resistance of the urethra to bacteria and thus cause infections. In addition, if the low immunity such as diabetes, long-term bedridden, the need to use immunosuppressants, or have a family history of genetic diseases, the usual bad habits of holding urine for a long time may cause urinary tract infections. There may be other causes of urinary tract infections, it is recommended that patients go to the regular hospital in time, after the cause of the disease is clear, under the guidance of the doctor to comply with the medical treatment.