The primary obstruction of the bladder neck is a condition which is diagnosed in many young people with symptoms of lower urinary tract, such as obstructive symptoms (difficulty in the initial phase of urination and urinary retention) and irritative symptoms (pollakiuria, dysuria and nocturia). These tests are needed for the diagnosis: uroflowmetry, urodynamics, rx urethrocystography. For the treatment are used alpha-blockers or surgery. The main diagnostic test is the urodynamic study. Even though the alpha-blockers are effective and safe drugs, sometimes the treatment is surgical. The gold standard is the transurethral incision of the prostate or bladder neck (TUIP), a technique with good results, but with some complications, including retrograde ejaculation, that is the most dangerous, and erectile dysfunction, that occurs in a lower percentage of patients. In this work was studied, in terms of forensic medicine, the case of a patient who is 35 years old and reported erectile dysfunction after an intervention of transurethral incision of the prostate or bladder neck. Although there is a limited possibility, documented in the literature, of erectile dysfunction as a result of TUIP, there is no sufficient evidence to confer the responsibility of patient's organic nature impotence to the health professional civil conduct which is directly related to the transurethral incision of the bladder neck, considering the presence of a lumbo-sacral disc disease in the patient, documented by CT two years before the surgery.