Increased segmental activity and intraluminal pressures in the sigmoid colon of patients with the irritable bowel syndrome.

Intraluminal pressure activity has been recorded in the unprepared true sigmoid colon of seven normal controls (mean age 37 years, range 22-55, three men) and seven patients with irritable bowel syndrome (IBS) (45 years, 24-75, four men) for 30 minutes before and 100 minutes after a standard 1000 kcal meal. Results differ from previously published data by showing much higher indices of pressure activity with amplitudes up to 490 mmHg in IBS, and 450 mmHg in controls. Study segment activity index and mean pressure wave amplitudes were significantly (p less than 0.015 and p less than 0.01) higher in IBS than controls, but per cent duration of activity was similar for the whole period of study. During the basal period in controls mean amplitudes recorded from the proximal sigmoid (40 cm from anus) were significantly (p less than 0.01) higher than those in the descending colon (50 cm), distal sigmoid (30 cm) and rectum (15 cm). This study shows that the increased colonic activity in IBS is characterised by increased amplitude, but not duration of pressure waves. In the basal state there is a high pressure zone in the proximal sigmoid colon of controls. Pressures in the unprepared colon of controls and IBS were higher than those measured under other experimental conditions.