Acute diarrhoea induces rectal sensitivity in women but not men.

Abstract

Some patients with diarrhoea predominant irritable bowel syndrome have increased rectal sensitivity. It is uncertain, however, whether the diarrhoea is a consequence of the rectal sensitivity or if it is sensitising the rectum in some way. The aim of this study was to assess whether inducing diarrhoea in normal healthy volunteers can sensitise the rectum and therefore be a potential or partial cause of the sensitive rectum seen in some patients with diarrhoea predominant irritable bowel syndrome. The anorectal responses to balloon distension were measured in 20 healthy volunteers (aged 20-43 years, 10 female) eight hours after laxative induced diarrhoea or under control conditions. Ingestion of an isoosmotic laxative increased stool output from 1.1 (0.7-2.3) (median (range)) to 8 (5-19) bowel movements per day with no significant differences between men and women. In women rectal sensitivity was significantly increased after diarrhoea compared with control conditions (vol to induce discomfort (ml): 116 (96, 136) v 153 (137, 168), mean (95°/O CI); p<0.001). This was associated with a reduction in the volume to induce internal anal sphincter relaxation (16 (12, 20) v 28 (21, 36); p<0.005), and volume to induce sustained internal anal sphincter relaxation (70 (56, 84) v 90 (67, 113); p<0.03), but no significant change in rectal compliance (ml/cm H20 at 100 ml) 4.8 (3.5, 6.1) v 4.1 (3.0, 5. 1) or distension induced motility (motility index) 994 (341, 1647) v 735 (46, 1424). Conversely, in men diarrhoea had no significant effect on anorectal physiology and their control values were not significantly different from those of the women. In conclusion, the results of this study taken with the finding that irritable bowel syndrome is more common in women, suggests that the male or female sex hormonal environment may be an important factor in allowing the gut to be sensitised to noxious stimuli. (Gut 1995; 37: 270-273)

The role of psychological and biological factors in postinfective gut dysfunction

“…There is some support for this from a recent study which showed that experimental induction of acute diarrhoea by laxative ingestion could sensitise the rectum in normal volunteers 42. However, the finding of these physiological changes in the asymptomatic group (IBS−) questions their relation to the experience of IBS symptoms by our IBS+ patients.…”

A role for inflammation in irritable bowel syndrome?

“…Sex differences have so far generally been neglected which is an unfortunate omission given that IBS is more frequently observed in females, 53 and that visceral hypersensitivity following episodes of acute diarrhoea can be induced in female but not in male patients. 54 The stimulus for further studies may come from recent data in patients with severe impairment of intestinal motor function which suggest that the inflammatory changes may involve neuromuscular tissue as well as the mucosa. [55][56][57] Preliminary data from patients with severe IBS symptoms indicated that an inflammatory infiltrate can sometimes be found in the myenteric plexus.…”

The menstrual cycle affects rectal sensitivity in patients with irritable bowel syndrome but not healthy volunteers

“…24 As an acute episode of diarrhoea induced by ingestion of an osmotic laxative is associated with an increase in rectal sensitivity in women (but not men), 25 and IBS patients seem to be more susceptible to sensitising events, [14][15][16][17][18] this may be the mechanism of the increased rectal sensitivity seen in IBS patients at menses. Alternatively, prostaglandins have been shown to induce afferent nerve sensitisation, 26 27 and as the gut of IBS patients may already be hypersensitive, prostaglandin release may be enough to trigger a further increase in this sensitivity.…”