Lower back pain can interfere with bowel habits without compression of the central canal (cauda equina syndrome which is highly searched for but rarely occurs). Increased intraabdominal pressure (required to create a bowel movement) will also increase lower back pain in certain situations. This can be misinterpreted as cauda equina syndrome.
Your mother may also have a bowel disorder. The specialists I am sure have looked for rectocele as one of the sources of your mother’s bowel problems.
Dr. Corenman