I was concerned cuz the indentation under his tail and above the rectum was filled with black/brown pastey stuff, and not knowing what it was, I took him to vet and turns out it's yeast. I didn't even know boy dogs got yeast infections!! The skin looks 'elephant' like around the area. Poor guy!! No wonder he's always whining for us to itch his butt!! Got some Monistat 7. Hopefully it works! Any more suggestions??