Question

I have a 3-year old Ragdoll, Fog, a neutered male, who had been the runt of the litter and has never grown to his expected size. One year ago, he lost a significant amount of weight-almost 2 pounds, bringing him down to about 8.5 pounds. He had been just over 10 pounds at his first well visit just after he had turned 1 year old. He was given every conceivable test-urine, blood, x-ray, ultrasound, and even a barium test to see if the problem lay in his esophagus. All tests have been normal. Prior to the ultrasound and barium test, we gradually changed his diet to Science Diet z/d under the assumption that he has a food allergy. (He had been eating Wellness hard food.) After 4-5 months on the z/d, he remained thin and continued to regurgitate. Vet suggests exploratory surgery next. Would it be okay to administer prednisone assuming it's IBS before preceding with surgery?