It's incredibly hard to do a necropsy without hitting something...especially if it's your first time. I think you did a fine job with good pics.I believe that was just the sloppiness of my dissection and poop spilling out. It wasn't there when I opened her up.
I will take a look at the links Wickededchicken6 thank you.

I'm sorry we were talking about your hen in such a way. I think we're a bit stumped about the stones.