I read on PubMed that fruit and vegetable skins, especially tomato skins, often get stuck in the bile ducts and clog them.
After I read that I thought, aha! They really are tomato skins! Which makes sense, because if you look at pictures of flukes they look nothing at all like the pictures people are posting of what is coming out of them. The flukes are fat and juicy like slugs, and the other things just look like skins. It's still good to flush them out, of course!