Physiological correlates of colonic motility in patients with irritable bowel syndrome

Irritable bowel syndrome is frequently encountered in clinical practice, and it has been repeatedly suggested that abnormal colonic motor activity is one of the major pathophysiological mechanisms responsible for the origin of symptoms in such disorder. If this statement is true, then high-amplitude propagated colonic contractions (HAPCs), i.e. the mass movements, may play an important role. To test this hypothesis, we conducted an investigation by recording colonic motility for a prolonged (24 h) period in 25 patients with irritable bowel syndrome and in 18 healthy volunteers, to compare the number of mass movements over 24 h in patients (constipation-predominant, alternating bowel habits) and controls. The overall amount of motility was also assessed in twelve patients and 13 controls. We also looked for the possible changes in mass movements and motility which may occur with defecation and after a meal. The results showed that 1) with respect to HAPCs and motility index, neither group was significantly different from controls; 2) HAPCs and the motility index were significantly reduced during sleep in all groups tested; 3) HAPCs were significantly more common before as compared to after defecation and after as compared to before meals; 4) HAPCs are not independent from the segmental contractile activity; 5) the motility index/24 h was lower in the constipation-predominant group of patients with respect to controls. We conclude that in patients with irritable bowel syndrome colonic motility per se may play a pathophysiological role in the genesis of the symptoms, although other mechanisms are likely to concur, or to be responsible for the complaints of these patients. However, colonic prolonged recordings are very useful for studying physiological and pathophysiological correlates of sleep, eating, and defecation.