Table 2

Alterations in colorectal motility and sensation in irritable bowel syndrome (IBS), and other functional bowel disorders

MeasurementMajor findings
Myoelectric activityIncreased long spike bursts in IBS diarrhea; irregular short spike burst activity in IBS constipation; myoelectric activity similar in IBS and “psychologic” controls and reported increase in 3 cycles/minute activity in IBS not confirmed.
Contractile activity and toneIncreased colonic phasic contractions postprandially in patients with IBS with prominent gastrocolonic reflex; increased colonic contractions in IBS constipation, reduced contractions in IBS diarrhea; lower rectosigmoid motility index in IBS diarrhea than controls, fasting and postprandially; increased rectosigmoid response to distension in IBS diarrhea > IBS constipation > controls; increase in high amplitude propagated (>35 mm Hg) contractions in functional diarrhea; fasting and postprandial colonic (descending) tone normal in IBS; impaired adaptive relaxation of the rectum in IBS in response to chronic distension.
ComplianceRectal and colonic compliance normal overall in IBS.
TransitAccelerated and delayed whole gut transit in IBS diarrhea and IBS constipation respectively; more rapid emptying of right hemi-colon in IBS diarrhea than in controls, related to stool weight; delayed colonic transit in severe functional constipation.
Colorectal sensitivity
 Conscious perceptionReduced threshold for pain and discomfort in rectum and colon in IBS; unusual somatic referral pattern.
 Cerebral blood flowIncreased dorsolateral prefrontal cortex blood flow in anticipation of rectal pain in IBS.
  • Modified from Drossman et al,14 with permission.

  • For references to relevant studies, see Chapter 3, tables 6 and 7. In: Drossman D, ed. Rome II: The functional gastrointestinal disorders. McLean, VA: Degnon, 2000 (in press).