O.K. I did some looking around, and it turns out that many people who have parasitic, bacterial, or "other" types of infection in the bowel {or are overly acidic} will cause the production of 'mucin' a type of polyprotein of some sort. Anyway, it's basically mucus which is designed to protect the bowel-lining. After many years it can build up to the point where many patients can suffer from chronic and painful constipation. It "hardens" like a thick rubber. This phenomenon is not always understood by the mainstream medical guys. I would think a colonoscopy whould reveal it. It must depend on the experience of the oncologist to spot this. I think you are right, that so many people have this, and it is difficult to see how thick it really is. So there you have it. As this stuff picks up debris and candida and whatever else over the years, it becomes a thick hard coating.
It is good that you are removing it, but remember you are also exposing fresh tissue. I would look into what is recomended for treating the suface of these tissues. You are on the right track, but I would slow down the cleansing for a while.