Assessment of the influence of dermatomal stimulation of the perception of rectal distension in healthy subjects with the irritable bowel syndrom

Research project P 13515 Perception of rectal distension during dermatomal stimulation Johann HAMMER 28.06.1999 Mechanical distension of the bowel evokes perception that becomes increasingly intense when the degree of distension is increased. For instance, in the rectum, sensation of stool and, when further dilated, urgency and pain, can be mimicked by distending a balloon in the lumen. Thus mechanostimulation with concurrent assessments of symptoms and measurement of distensibility are being employed increasingly in the evaluation of intestinal symptoms such as the irritable bowel syndrome (IBS). Up to 94% of patients with IBS have a lowered perception threshold to balloon distension in the rectum. The neural pathways underlying rectal hypersensitivity to balloon distension are not known, however it has been shown that central perception mechanisms are altered in patients with IBS. I want to assess whether a central mechanism of perception, that is spatial summation, which has been shown to be present on the skin and in the small intestine, plays a role in rectal mechanoreception in healthy subjects and in the altered perception threshold in patients with IBS. I also aim to include an assessment of the effect of dermatomal stimulation by electroacupuncture on rectal mechanoreception in healthy subjects and patients with IBS. Rectal tone and sensory thresholds for rectal distension will be measured in healthy subjects and in patients with IBS using two different sizes of polyurethane bags and a dual barostat. The effect of electroacupuncture of adjacent and distant acupuncture points on rectal tone and sensory thresholds for rectal distension will also be evaluated. Cutaneous referral of rectal symptoms will be determined in healthy subjects and patients with IBS. This study will give new insights into the neurophysiology of normal rectal sensation and into the pathophysiology of IBS in general and into the pathophysiology of rectal symptoms in patients with IBS in particular. In addition, the effect of dermatomal stimulation by electroacupuncture on rectal physiology will be investigated and thus the therapeutic role of electroacupuncture in IBS will be investigated.

Acupuncture in dermatomes has an effect on rectal sensation by increasing sensation thresholds Patients with the irritable bowel syndrome (IBS) often receive acupuncture although no scientific data exist to support this therapy. In our study we were able to show that both electroacupuncture and placebo-acupuncture did, compared to the protocol arm, where no acupuncture was applied, increased thresholds for sensations arising from the rectum. However, objectively measurable parameters, such as distensibility of the rectum, were not changed by acupuncture.