In men, the inner urethral lumen is about 11 millimeters, the width of the membranous part of the urethra is about 9 millimeters, and the width of the outer urethral opening is about 7-9 millimeters, which varies from person to person. The male urethra has the function of ejaculation and urination, starting from the internal urethral opening in the bladder and ending at the external urethral opening in the penile area. The male urethra is divided into 3 main parts, which are the prostate, membranous, and corpus cavernosum. The length of the adult male urethra is generally about 18 cm, but the overall width is not uniform, the normal urethra has three narrow parts, of which the width of the internal urethral canal lumen belongs to the widest, probably around 11 mm, the membrane part refers to the part of the urethra that passes through the urogenital septum, the width of the urethral membrane is around 9 mm, the width of the urethral external orifice is around 7~9 mm. The male urethra as a whole presents S-shaped curvature, when doing endoscopic operation check, need to pay extra attention to the narrower parts of the male urethra, so as not to cause damage to the urethra.