Why appendicectomy is protective factor in ulcerative colitis?
UC cause continuous ulcers starting from rectum and going backward to entire colon and can also involve ileum then(called backwash ileitis) . So if you create a barrier in between by doing appendicectomy it may prevent further disease spread .
Crohn’s on other hand cause skip ulcers which can involve from lips to anus so doing appendicectomy has no impact on disease course