Pathophysiology of Bowel Dysfunction in Patients with Motor Incomplete Spinal Cord Injury: Comparison with Patients with Motor Complete Spinal Cord Injury

Purpose: Bowel dysfunction is a major problem in patients with spinal cord injury. Previous work has provided partial information, particularly about motor incomplete lesions. The purposes of this study were to evaluate the pathophysiologic features of neurogenic bowel in patients with motor incomplete spinal cord injury and to compare them with those in patients with motor complete lesions.

Methods: Fifty-four patients (59% men; mean age, 43 years) with chronic spinal cord injury and fecal incontinence and/or constipation were evaluated; 32 had motor incomplete lesions, and 22 had motor complete lesions. Clinical assessment, colonic transit time, and anorectal manometry were performed.

Results: Colonic transit time was delayed similarly in patients with motor complete lesions and those with motor incomplete lesions. Anal squeeze pressure was present in most patients with motor incomplete lesions and absent in all patients with motor complete lesions. The cough-anal reflex was less frequent in patients with motor complete lesions with a neurologic level above T7 (P < 0.05). Rectal sensitivity was less severely impaired in those with motor incomplete lesions (P < 0.05). Most patients in both groups did not show anal relaxation during defecatory maneuvers. Rectal contractions and anal sphincter activity during distention of the rectum were detected more often in patients with motor complete lesions (P < 0.05).

Conclusion: Many severe pathophysiologic mechanisms are involved in neurogenic bowel, affecting patients with motor incomplete spinal cord injury similarly to those of patients with motor complete lesions with spinal sacral reflexes. The pathophysiologic mechanisms of constipation are obstructed defecation, weak abdominal muscles, impaired rectal sensation, and delayed colonic transit time; the mechanisms of fecal incontinence are impaired external anal sphincter contraction, uninhibited rectal contractions, and impaired rectal sensation. However, specific evaluation is required in individual cases.