When I had my GB removed and my liver opened, I had a total meltdown in my digestive system and I spent a lot of time on my throne. The doctor told me to eat salad and fat free or low fat foods. I had a LOT of trouble keeping the food down, and when I did, I noticed that I was not digesting the lettuce at all. Since then, I have been on Curezone and inspecting what happens to what I eat when it comes out, and I've noticed that lettuce and some other leafy greens do come out that way. I think you might be right about it being old lettuce. I really don't think there are any parasites that look like that. They are usually cylindrical or pod-like or seedy looking.