The length of male urethra insertion is about 15-20cm, and the length of normal adult male urethra is about 15-17cm. The urethra is divided into the anterior urethra and the posterior urethra. The anterior urethra is divided into the overhanging urethra of the penis and the bulbous urethra; the posterior urethra is divided into the membranous urethra and the prostatic urethra. The urethra seen is mostly the overhanging urethra of the penis, the rest is located behind the pelvic cavity and cannot be seen by the naked eye. In men, the urethra is still relatively long, and when a urinary catheter is left in place, in principle, urine must be seen to flow before it is considered to be inserted into the bladder. If you calculate purely on the basis of length, even if the insertion is about 15-20 cm, you still do not see urine flow. It is recommended to continue feeding the urethral tube forward until urine flow is seen to ensure that the tube is fully inserted into the bladder. The length should only be used as a reference value and not as an absolute standard.