In the human body, under normal conditions, there is a closed urethral pressure, so the urethra is closed and no retrograde bacterial infection occurs. However, during catheterization, as the urinary catheter can leave the human urethra in an open state, once this urinary tract infection is secondary, it can easily cause an upstream infection of the urinary system. Therefore, once a urinary tract infection occurs after catheterization, the patient should be treated promptly and, if necessary, the catheter should be removed and adequate anti-inflammatory and symptomatic treatment should be given before the urinary tract infection can be relieved. If a patient develops back pain, fever and percussion pain in the kidney area, it may be secondary to an upper urinary tract infection, such as pyelonephritis, which usually has more serious symptoms and should be treated promptly. If the treatment is not timely, it may cause the infection to enter the blood circulation and sepsis, or even the possibility of septic shock.