I would think maybe this would be good for a quick fix, but I wouldn't recommend leaving it in there for more than a short period or it could irritate the inside of their rectum and start to break down the surrounding tissue. Even though the balloons on the rectal tubes look big they are specifically made to sit properly and not cause breakdown on the inside.
We use them in my trauma icu all the time. They are great! The stool has to be liquid, duh, but it helps keep their skin intact. Heck I had a pt with an upper GI bleed who was A&O x 4 who was mortified to have to get onto a bedpan (was on bedrest). I suggested the trumpet, she said she'd try and she loved it! Very helpful when your pt has black watery stool. We have to have an order for it, but usually day shift gets it for us, docs would have our heads for calling for one in the middle of the night!