Unfortunately, there can be some negative side affects to massaging the urethra. The urethra is highly sensitive and is easily irritated. Even normal intercourse can irritate a woman's urethra, resulting in painful urination and infection. This is especially true of virgins and women with tense pelvic muscles as they are too tight, resulting in there being too much friction between their vagina and the thrusting penis or dildo. Intentionally stimulating the urethra increases the chances of there being irritation and infection. To help prevent infections and reduce the chances of irritation, a woman should drink lots of water and urinate just before and right after urethral stimulation, or sex in general if you are prone to urinary tract infections. Just release a little bit of urine before sex if you are trying things with a full bladder. They also recommend women drink cranberry juice, or take a cranberry supplement, as its acidic level helps to ward off the bacteria that cause infections. If you experience irritation, painful urination, or infection, try using less pressure when massaging or stimulating the urethra. The urethra may become accustomed to the stimulation with time, but do not torture yourself, or inflict multiple infections. Have fun, but do not hurt yourself.