Suggest Treatment For Having Opening In The Skin On Tailbone

My boyfriend is 6 feet 1 inch and 240 pounds. He went to the ER last night because his tailbone had been hurting very bad and then liquid was leaking from it. He forgot what it is called and I am curious what it is. The doctor said it is a disease and only surgery will make it go away. It's a disease where there is an opening in the skin on the tailbone, and it can get bigger and bigger if left untreated.