Is it possible that a full colon impinges on the sciatic nerve? Is there anything that physically separates the sciatic nerve from the colon?
Sciatic nerve pain cannot be caused by a full colon.
The sciatic nerve runs at the back of the pelvis down the the leg. The sciatic nerve exits the spine from the lumbar spine to S3 in the sacrum (Fig. 1).
Fig.1. Left: sciatic nerve overview. Right: Sacral plexus. Source: Manchester Bedford Clinic
Hence the sciatic nerve does not come into contact with the bowel and intestines located ventrally in the abdominal cavity (Fig. 2).
Pain in the sciatic nerve (sciatica) is often caused by compression or entrapment by muscles, tendons, and other soft tissues along the nerve path Manchester Bedford Clinic.