@toby77 Thanks Colleen for inviting me to this discussion. Toby, What stands out in my mind is that you have have several abdominal surgeries, and all surgery creates scar tissue, and internal scar tissue in the connective tissue and fascia. There can be adhesions in the connective tissue that supports the colon. It is tied in there normally and can move a bit, but is not loose to roam around like a bowl of noodles. If you get the GI tract moved and stuck in an unusual position it can cause problems. The other thing that affects the colon is when the hip flexors get tight from sitting too much, it compresses the area where the colon is on the way to the exit. It gets overly tight right on the inside of the pelvis hip bones. You would be able to tell this if it's tender there, and if your walking strides are shorter and your leg doesn't extend backward enough, or if stretching it back while standing like in a lunge position is tight.

What I think could help is physical therapy with a PT who understands myofascial release which is a way to stretch out tight fascia and connective tissue. That sometimes can help a posture related kyphosis a little bit, and it can release tightness in the chest. I have breathing issues related to chest muscle tightness because of thoracic outlet syndrome, and MFR work does help that. Frequently my PT releases the diaphram and elevated first ribs when I start using my neck muscles for accessory breathing. It's common that the front of the chest can be too tight as we do so much forward with our head and arms, and forget to stand up straight and stretch. I have had chest tightness and spasms that caused chest pain and I don't have heart disease (confirmed by doctors).

Here is our discussion on MFR
– Myofascial Release Therapy (MFR) for treating compression and pain https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/

and there is a provider search at https://www.mfrtherapists.com/ .

That could be a place to start, and a PT is also a good source to help identify and narrow down issues. A PT can also work on your neck. The phrenic nerve exits the spine up around C3 traveling downward toward the lungs and there could be tightness in the neck or chest compressing it. That is where myofascial release may help by loosening a tight neck and chest. If the phrenic nerve is paralyzed and non functioning, there is a surgeon who does nerve graft surgery to replace the phrenic nerve. I don't have experience in that, but other members have posted the information so I can share the website here.
https://www.advancedreconstruction.com/
Have you heard of myofascial release therapy before? Does that sound like something you would like to try?