Colon polyps more frequently in the lower part: Why?

From some cursory browsing, I think I have gathered that polyps are more common in the lower part of the colon than upper, but I’ve been missing why that’s the case, or if it is known. Anyone???

I’ve been told it’s because it’s closer to the muscles, and thus more likely to have been affected by straining. I don’t know if it’s accurate, but I don’t like seeing a GQ with no replies.

Maybe that’s a theory based on the fact (?) that the lower intestine is as far as the endoscopes go. My polyps were way up there.

Apparently polyps are linked with vitamin D deficiency. IANAD, but this is a theory from some casual reading I did: the lower down the colon you go, the less vitamin D would be left to be absorbed (if you don’t have enough of it, you’d run out before the stool is excreted). Also, less water remains the lower stool gets. It’s plausible that, due to a combination of drier, more abrasive stools, and less vitamin D to be absorbed, the lower half of the colon is more likely to deteriorate first.

It could also, more simply, be due to the fact that the lower intestine is narrower than the upper. Maybe polyps form in the upper just as often, but cause problems more rarely because they take up less space (as a percentage of intestinal width), meaning they get abraded less.

Any answer is likely to be speculative, since it’s not definitively known what causes polyps in the first place.

Colonoscopes (the ones they use for colon-cancer screening) go all the way to the connection of the small intestine to the large intestine, so they see the whole mess. I just spent a day watching 8 of them!

SWAG: any carcinogens in the contents are concentrated in the distal end of the colon as residual water gets absorbed.