The ulceration by these drugs in the intestine, colon, rectum or anal canal followed by healing of the ulcers may lead to strictures or narrowing of the diameter of the lumen of the gut. On occasions, this narrowing can become significant enough to impede the movement of bowel contents downstream and require some type of therapeutic intervention. Lactose intolerance is a relative deficiency of the enzyme lactase which digests lactose present in dairy products. A cup of milk a day can be tolerated by most people. Yogurt although a dairy product is well tolerated even by lactose intolerant subjects.
Frozen yogurt is less well tolerated although it is better tolerated than milk.
Like someone said, Surgery is only minor so long as it is performed on someone else . Same is true for these procedures of endoscopy and liver biopsy. I have been involved with literally thousands of these procedures. In general, it is true that these are safe procedures. But safety is a relative term.