Rectal hyperreactivity to distention in patients with irritable bowel syndrome: role of distention rate

Rectal motor hyperreactivity to distention may be involved in the pathophysiological course of defecatory symptoms in patients with irritable bowel syndrome (IBS), but results of patient studies are conflicting, possibly because of differences in the applied distention rate. Because a fast rate of distention increases the rectal motor response in healthy subjects, it also may show hyperreactivity in patients with IBS. The aim of this study is to compare the effects of 2 distention rates on rectal motor responses and sensations in 16 patients with IBS and 12 healthy subjects.

Rectal distensibility and the frequency of rectal contractions and sensations were recorded during volume-controlled rectal distentions at 2 distention rates (10 and 100 mL/min).

Recta of patients with IBS were significantly less distensible than those of healthy subjects during fast distention (P = 0.0006), but this difference was not statistically significant during slow distention (P = 0.07). The frequency of rectal contractions and sensations, the majority of which were sensations of gas and a desire to defecate, were significantly greater in patients with IBS during both slow and fast distentions (both P < 0.025).

Recta of patients with IBS are hyperreactive to distention, and fast distention magnifies this abnormal motor response. A greater frequency of sensations during a fixed-time distention period may help to characterize the patients.