Indications for indwelling catheter: 1. When patients have acute difficulty in urination due to various reasons, indwelling catheter is needed as an emergency measure to achieve the purpose of relieving patients’ difficulty in urination, such as acute urinary retention caused by prostatic hyperplasia and urinary retention caused by obstruction due to urethral stones. 2. Intraoperative indwelling catheter is needed for various surgeries lasting more than one hour to facilitate the anesthesiologist to record the patient’s output. After surgery, patients are mostly bedridden and cannot go down to urinate. It is necessary to keep catheter after surgery. If a urinary catheter is not left in place after urethral surgery, the surgical scar may be stenosed again during the healing process and lead to surgical failure. Wait for the wound to heal completely locally and remove the urinary catheter after the completion of shaping to achieve good surgical results.