In years past I have had each a colonoscopy and a sigmoidoscopy performed at different times. The sigmoidoscopy only went as far as the sigmoid portion of the intestine, as I understand it.
The colonoscopy, however, did run the entire length of the colon (and certainly cost a lot more than the sigmoidosocopy, I might add), pretty much up to the appendix area close to where the small and large intestines merged. This was especially important to me at that time since my mother had been recently diagnosed with colon cancer in that area and I was concerned about myself due to my history of chronic constipation.
I also know the colonoscopy covered that tract because the doctor performing it kept rousing me to either turn my body to accomodate the bends in the colon (and man, do I remember feeling it make those turns!), and he was also excited and wanted me to watch the camera monitoring the intestinal trip. I later regretted that I had asked so many questions before the exam, because he seemed hellbent on giving me, in my very drowsy state, a running show-and-tell lecture about my colon, inch
(it seemed). btw, my intestines were a "pretty" pink, which I thought was neat until I later learned the pinkness is not natural for that area and the color was due mainly to the irritation from the laxatives and the device inserted for the exam.
I didn't see any plaque, nor do I remember any mention of the plaque ever being brought to my attention, although I can pretty much guarantee I had (and still have) mp. There is some explanation for the plaque being undetected in these exams, although I can't recall exactly what it is (sorry). I think it has something to do the body's process of continually laying down more and more mucus to neutralize the toxins continually being run through the colon, which is why a person tends to become increasingly constipated or having problems due to the multiple layers of plaque that have built up over the years. This information came from a discussion with a colon specialist like PTree (although not her) who had been working with this stuff for years and was knowledgeable of alternative healing methods (certainly not the doctor!).
I would imagine, though, as Zule suggested, that there is plenty of material or plaque in the pockets of the colon alone to make a p&b cleanse warranted, in my opinion. This is just my experience and understanding, but hopefully open to change the more I learn. Hopefully someone can further explain this process.