Retrograde ejaculation usually refers to retrograde ejaculation. Retrograde ejaculation is when semen does not exit the body through the external urethral opening, but instead flows retrograde into the bladder. The sudden appearance of retrograde ejaculation may be related to urethral injury, prostate surgery, medications, and so on. 1. Urethral injury: for example, lower urinary tract stones or urethral tumors lead to urethral stenosis, when the patient ejaculates due to urethral stenosis, resulting in urethral pressure is too high to ejaculate semen normally into the urethra, leading to retrograde ejaculation of semen into the bladder. 2. After prostate surgery: prostate surgery may damage the urethral sphincter, there is an incomplete closure of the internal urethral sphincter, there will be a retrograde flow of semen into the bladder. 3. Drugs: drugs such as Serodosin capsules can relieve smooth muscle tension in the lower urinary tract tissues, so that when ejaculation occurs, semen does not ejaculate out of the body through the urethra normally, but flows into the bladder through the loose bladder neck, and retrograde ejaculation occurs. There may also be other reasons for sudden retrograde ejaculation, it is recommended to consult a doctor in time, with the help of the doctor to clarify the cause, and targeted treatment or therapy.