I have seen this come out of me. It IS the lining of your sMall intestine being shed.
This means you have Celiac Sprue.
You can get tested for it. There is a blood test that is then followed by a biopsy of your small intestine.
I didn't do the testing because it is not 100% accurate and I did not want to suffer any longer. There are several web sites dedicated to Celiac disease you can read up on it.
You can not tolerate gluten. Genetically your body attacks itself when you consume gluten. You can't abdorb nutrients that are suppose to be absorbed in the small bowel. You must stop eating anything with gluten immediately. This is not easy as it is not just bread. Gluten is in everything.
This disorder nearly killed me before I finally got it under control. The final key was taking large amount of folate (do not take folic acid)and B12 to compensate for the damaged intestine that wasn't absorbing nutrients.
I kept going into denial and then getting sick as hell over and over. I've finally fully accepted it and I have never felt better.
Read up. It can kill you but deaths are rare.
Celiacs are at increased risk of lymphoma.
Doctors are so stupid.
They should have at least done a blood test for gluten antibodies. It sucks but it is what it is. Good Luck. It takes years of gluten free eating to completely heal.
Doctors roll their eyes when you tell them you think you have Celiac Sprue because they think its a fad.
Sorry, pooping my intestinal lining was the clincher for me.