Gut contents were obtained from two sudden-death victims...The wet weight of colonic contents, in subjects 1 and 2 respectively, were: caecum, 71.9 and 18.2 g; ascending colon, 86.5 and 11.9 g; transverse colon, 125.7 and 25.3 g; descending colon, 3.68 and 126.9 g and sigmoid/rectum, 56.6 and 6.1 g. Total wet weights of colonic contents were 344.4 and 188.4 g.
Those Ads were popular on TV years ago. They all claim some permanent build-up of "extra poop" which only a cleanse can remove. I found a lovely 2018 quote from a skeptic medical office of McGill University from the head, a Chemistry instructor. The lead-up to it is quite funny and mentions earlier Ads. This part makes one embarrassed to have even considered lingering poop:
Now let’s get real here. Have pathologists who have carried out
thousands of autopsies seen pounds of goo encrusted in intestines? No.
Have colo-rectal surgeons who have operated on colons thousands of
times seen such sludge? No. Have radiologists who have perused
thousands of x-rays of the colon noted the buildup of “mucoid plaque?”
No. Why? Because it doesn’t exist. The term itself was the invention
of naturopath Richard Anderson who created Arise and Shine, a popular
Not a proof, but he's reminding us of what we should know: the colon isn't some obscure part of the body no one has ever looked at before.
A search on Mucoid Plaque leads to a Wikipedia entry, funny but not as funny as the article above, with:
While colonic irrigation enjoyed a vogue in the early 20th century as
a possible cure for numerous diseases, subsequent research showed that
it was useless and potentially harmful [...] ( Ernst, E (June 1997). "Colonic irrigation and the theory of autointoxication: a triumph of ignorance over science". Journal of Clinical Gastroenterology. 24 (4): 196–198).
Then later directly addressing the "pounds of stuck poop":
claims that waste material can adhere to the colon, Douglas
Pleskow, a gastroenterologist at Beth Israel Deaconess
Medical Center, stated, "that is the urban legend. In
reality, most people clear their GI tract within three
days." (Foreman, Judy (June 30, 2008). "Beware of colon cleansing claims". Los Angeles Times).
So there's no extra poop. Food goes in, and at most 3 days later it's all out.