Anytime when scar tissue and adhesions are cut off through surgery, new ones form after a period of time, because this is the body's reaction to injury. If this is not absolutely necessary - e.g. you have obstruction of bowel - I would not advise having it.
The Liver and the system in whole are dealing with detoxing while fasting, nutritious reserves are getting down, the heart has to adapt to different way of working. I do not think that either I or your doctor and anesthesiologist can predict how much toxins/challenge in the form of drugs and cutting/laser your body can withstand under fasting. Most probably you will have a serous crisis and very likely a misguided attempt by the hospital to bring you in balance afterwards, while not exactly understanding the root of the crisis or not having experience dealing with it.
Simple analogy: This why a person doesn't have a planned surgery for hernia while at the same time being treated for massive malnutrition. You need to give one or the other priority. It is like wanting to run a marathon, while at the same time you want to compete in ski-jumps. Physically it is extremely taxing, not to say impossible.