Semen loss in urine, possible causes: 1. If the patient has a history of urethral surgery, such as electrodesection of the prostate or bladder neck incision, it can cause retrograde ejaculation. After surgery, the pressure on the bladder neck is reduced, the posterior urethra is open, and semen can enter the bladder retrogradely during ejaculation. The typical presentation is that the patient has orgasm, but no semen is expelled. Semen can be seen in the urine in the subsequent urination, which is a common complication after urethral surgery.2. If the patient has had urethritis, urethral infection, or has urethral stones, polyps and other changes that cause elevated resistance in the urethra, there can also be no semen discharged from the urethra during ejaculation, but enters the bladder with urine discharge, accompanied by symptoms such as frequent urination, urinary urgency and painful urination. Routine urinalysis and urethroscopy are needed to further clarify the presence of urethra-related lesions.