mucoid plaque: true or not true?

I've read that from the conventional medicine stand point, doctors don't believe in 'mucoid plaque' - can someone explain to me: if there is mucoid plaques in the colon, why can't you (or your doctor) see it during colonoscopy or sigmoidoscopy? The colon wall color is just pink - not black like the built up plaque that's claimed to be the mucoid.

I've done my own bowel cleansing with Bentonite and psyllium, and juice fast for a week. All I consumed as sort of 'solid' intake was the Bentonite and psyllium.- and YES I passed lots of this "mucoid plaque" and they look pretty nasty - And when I did go (you know), all that came out was just the this mucoid plaque (dark grey nasty thing).
I wonder if that's just the result of Bentonite and psyllium being digested?

Thanks for enlighten me about this.