The inability to urinate or difficulty in urinating after an erection is related to the anatomy of the urinary system. It is simply caused by the congestion of the prostate gland compressing the urethra so that its pressure exceeds the internal bladder pressure.
The process of urination, specifically, is that the bladder forced urethral muscle undergoes contraction during urination, which increases the pressure inside the bladder, and the sphincter of the bladder neck and external urethral orifice diastole, which leads to a decrease in the pressure inside the urethra, and when the pressure inside the bladder continues to increase over the internal pressure of the urethra, the urine can be discharged.
And in the state of penile erection, due to the continuous congestion of the prostate gland, penile corpus cavernosum and other parts of the penis, it will compress the urethra, resulting in an increase in its pressure over the intravesical pressure. It will cause difficulty and effort to urinate.
Specific reasons for not being able to urinate, but also need to go to the regular hospital to do the relevant examination.