What level of SCI would cause severe constipation?

What level of SCI would cause severe constipation?

• A. T-12.
• B. S-2.
• C. C-5.
• D. L-2.

Answer: (B)

Defecation relies on reflex pathways that originate in the sacral spinal cord, specifically the parasympathetic fibers from S2 to S4 that stimulate distal colon motility and relax the internal anal sphincter. When the injury involves these sacral segments, the reflex defecation loop is disrupted. An injury at S2 interrupts the pelvic parasympathetic outflow to the distal bowel, reducing peristalsis in the rectum and hindering the sensation of stool filling. Without that reflex-driven propulsion and guidance, stool accumulates and evacuation becomes difficult, producing severe constipation. Injuries higher up the cord still affect voluntary control but leave the sacral reflex pathways intact, so patients often retain some reflex defecation and may manage with stimulation or bowel programs, though constipation can still occur.

Defecation relies on reflex pathways that originate in the sacral spinal cord, specifically the parasympathetic fibers from S2 to S4 that stimulate distal colon motility and relax the internal anal sphincter. When the injury involves these sacral segments, the reflex defecation loop is disrupted. An injury at S2 interrupts the pelvic parasympathetic outflow to the distal bowel, reducing peristalsis in the rectum and hindering the sensation of stool filling. Without that reflex-driven propulsion and guidance, stool accumulates and evacuation becomes difficult, producing severe constipation.

Injuries higher up the cord still affect voluntary control but leave the sacral reflex pathways intact, so patients often retain some reflex defecation and may manage with stimulation or bowel programs, though constipation can still occur.