Do prostate diseases affect how men pee? how do they quantify their symptoms?

Yes they can.: Due to the location of the prostate at the outflow point of the bladder, diseases of the prostate often present as urinary problems. These symptoms are usually quantified by questionnaires which are scored. A common one used by urologists is the international prostate symptom score (ipss or auasi). This is based on 7 questions about urinary symptoms and bother.