PHILADELPHIA — Patients with low back pain had a significantly greater prevalence of bowel motility disorders, compared with patients with chronic shoulder pain in a study with 98 patients.
“Our findings suggest that nervous pathways involved in relaying pain in the lumbar spine affect the transmission of sensations from the bowels, causing bowel motility disorders” such as diarrhea, constipation, or bloody stools, Sergio A. Mendoza-Lattes, M.D., reported in a poster at the annual meeting of the North American Spine Society.
The findings suggest that patients with low back pain should be assessed for bowel motility disorders, concluded Dr. Mendoza-Lattes and his associates at the Uni- versity of Iowa in Iowa City.
A link between low back pain and bowel motility disorders was suspected because many symptoms of gastrointestinal disorders result from altered sensory perception in the bowels.
Somatic afferent neurons firing in the spinal cord can inhibit viscerosomatic neurons in the dorsal horn from responding to stimuli. A prolonged somatic irritant, such as low back pain, that acts on afferent fibers from the gastrointestinal tract might inhibit sensations of visceral pain and lead to bowel motility disorders.
This hypothesis was tested by studying 59 patients with low back pain and 39 patients with shoulder pain who were seen at the orthopedic clinic at the University of Iowa. The study excluded patients with a history of lumbar spine or abdominal surgery.
The average duration of low back pain in these patients was 22 months, and the average duration of shoulder pain was 23 months. The two groups were similar in demographics and comorbid conditions, and in the frequency they used analgesics and muscle relaxants for their pain.
The patients with low back pain were 2.2 times more likely to have bowel motility disorders than the patients with shoulder pain, a statistically significant diff- erence, reported Dr. Mendoza-Lattes, an orthopedic surgeon at the University of Iowa.
The patients with low back pain were also 2.3 times more likely to use antidepressive, antianxiety, or mood-altering medications, but the use of these medications showed no correlation with the prevalence of bowel motility disorders.
Among the patients with low back pain, the use of opiates was linked with a significantly reduced prevalence of bowel motility disorders. Among those using narcotics, 25% had bowel disorders, compared with a 62% prevalence among those not using opiates. This finding suggests that the link between low back pain and bowel disorders is reduced by using opiates.