In a patient who had pelvic radiation for prostate cancer, which mechanism for bowel continence is most likely disrupted?

In a patient who had pelvic radiation for prostate cancer, which mechanism for bowel continence is most likely disrupted?

• A. Functioning of the pelvic floor musculature.
• B. Compliance of the rectum.
• C. Integrity of neural pathways.
• D. Quality of internal anal sphincter.

Answer: (B)

Radiation to the pelvis often damages the rectal wall and causes fibrotic stiffening. The important point is how the rectum serves as a compliant reservoir that can stretch to hold stool between defecations. When fibrosis reduces this distensibility, the rectum cannot accommodate as much content, so stool reaches the rectum with less warning and continence is more easily lost. This loss of rectal compliance is the mechanism most likely disrupted after pelvic radiation. Pelvic floor muscles contribute to containment and support, and neural pathways or the internal anal sphincter play roles in tone and sensation, but the change most directly linked to radiation is reduced rectal compliance due to fibrotic stiffening.

Radiation to the pelvis often damages the rectal wall and causes fibrotic stiffening. The important point is how the rectum serves as a compliant reservoir that can stretch to hold stool between defecations. When fibrosis reduces this distensibility, the rectum cannot accommodate as much content, so stool reaches the rectum with less warning and continence is more easily lost. This loss of rectal compliance is the mechanism most likely disrupted after pelvic radiation.

Pelvic floor muscles contribute to containment and support, and neural pathways or the internal anal sphincter play roles in tone and sensation, but the change most directly linked to radiation is reduced rectal compliance due to fibrotic stiffening.