I’ve had a colonoscopy (without pain relief) where they took biopsies. The doctors said the biopsies wouldn’t hurt because the colon couldn’t feel pain, and they were indeed painless. The amount of air they pumped in was horrifically painful however.
Trapped gas sounds trivial, but can also be extremely painful. Ulcerative colitis also hurts. So does diarrhoea.
So how do these pain mechanisms work? What causes the pain, if the interior of the colon is unfeeling?
In: Biology
You ever stub your toe really hard and have the thought, “crap, this is really gonna hurt.” The reason you “know” you stubbed your toe before you feel any pain is because the nerves that carry the sensory information that tells you where your foot is in space, what your foot is touching and that you just bumped it are different nerves than the nerves that tell your brain that there is pain. The first type send a signal much much faster than the pain type (the ELI5 for nerve conduction speed is a completely different conversation but also fascinating).
In short, different nerves send different signals and the nerves that send the signal for “pain” in the traditional sense (eg, cutting your finger) simply aren’t present in the bowel.
For more info, you can explore topics like: somatic vs. autonomic nerves, autonomic nervous system, enteric nervous system, referred pain, proprioception. I also recommend writing by Oliver Sacks and VS ramachandran if this type of stuff is interesting to you. Enjoy!!
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