This is a surgical procedure. I don't feel "Remove Gallstone" as a domain is any more desirable than having "Remove Appendix", "Remove Spleen" ...unconvinced
People go to a local hospital or clinic. Those in this field aren't running under "Remove Gallstone" as a domain. Besides that, it is typical for surgeons to be qualified at doing more than just gallstone removal, in their profession, which limits it
Reg fee territory, sad to say ...in my opinion. Sorry