Having just had ileostomy surgery, I remembered seeing this thread. A couple of days after my surgery, I passed a solid stool. The next couple of days, this bloody black mess. In the following days, I passed completely clear mucus, a few times a day. It would give me the same urge as if I needed to have a bowel movement, but required no straining (I used to have to strain a lot, even with diarrhoea), as soon as I sat on the toilet and relaxed my muscles, it would slip out.
The nurses, doctors and stoma nurse all told me this is all completely normal. The past four or five days, I've passed nothing from the back passage at all - it seems the mucus has stopped. It's such a huge relief knowing I'm never going to have to pass anything that way again!
The advice I was given, though, was that usually, mucus clears up after several weeks (it seems I've stopped passing it now, but I'm bearing in mind this might just be a temporary absence at the moment) - they said it almost always reduces to nothing or next to nothing. I'm guessing the type of ostomy you've had and where you have active disease still may be a feature though.