Accutane can cause major disruption to the intestines/bowel etc. Ulcerative colitus can occur in people, especially for those prone to it through genetic heredetry. I know it's only a n extreme case, but the colon ( large intestine/gut) can become so inflammed an ulcerated, surgery to remove it can be an only option of drugs don't cure it, which means you'll have a bag strapped to your stomach for the rest of your days.