Urinary tract infection is a common infectious disease of the urinary system. According to the location, urinary tract infection can be divided into upper urinary tract infection and lower urinary tract infection; upper urinary tract infection refers to inflammation of the kidney and ureter; while lower urinary tract infection refers to inflammation of the bladder and urethra. Lower urinary tract infections mainly refer to bladder and urethra infections. The main cause of lower urinary tract infections is retrograde infection, which means that bacteria enter the urethra and bladder retrogradely from the urethra, and the infection is caused by unclean sex, women with vaginitis or men with glansitis, as well as catheterization and cystoscopy without strict aseptic medical operation, resulting in bacteria entering the urethra and bladder from the This is caused by bacteria entering the urethra and bladder through the urethra. Upper urinary tract infections are mainly caused by inflammation of the kidney and ureter. The main causes of upper urinary tract infections are infection of the kidney by bacteria in the bloodstream or obstruction of the upper urinary tract, such as kidney tuberculosis, or kidney infection caused by hydronephrosis due to kidney stones. In summary, the main cause of lower urinary tract infections is retrograde bacterial infection, while the main cause of upper urinary tract infections is bloodstream infection or urinary tract obstruction.