Probably a colorectal surgeon, but not necessarily, just a good place to start.
What type of surgery is expected? Laparoscopy? open abdomen? Resection? Strictureplasty? How many of the expected type of surgery has he/she done? How many does he/she usually perform in a year of this type of surgery? Does he/she have an assistant surgeon? What part of the surgery does the assistant do? How many of this type of surgery has the assistant assisted at?