I have a black mark near exit area of bladder. It hasn t t faded yet. I had bladder ca this past year. Just recently had my four month check up with dr Patel at Kaiser. No ca and no ca in blood test. I always have burning bad. After they put lubricant on and it s still hurts . Still quite red there then this really black at near opening of bladder was there and still is after three weeks. I also had thyroid ca last year. And I also have m.s.. I take a lot of pills. Thanks for your input, I told dr and he said nurse will call me. But I missed her calls. And my dog. Got sick and I was cleaning up throw up of my dog.