Hi, I am sorry to hear about this happening to your son. I have had the same symptoms and string looking things in my stool as well as in my pleghm for almost a year now. It's very disconcerting that these things could possible be in my lungs. Did you guys ever recieve a diagnosis? I've been to countless doctors and all have sent me home and laughed me out the door saying that I am just overreacting. :( It sucks and I really hope you were able to get some answers because I know how it feels! I feel like I've aged 10 years because of my constant worrying!