Somatostatin analog inhibits afferent response to rectal distention in diarrhea-predominant irritable bowel patients

Abstract

Irritable bowel syndrome (IBS) patients exhibit enhanced sensitivity to rectal distention. The somatostatin analog reduces perception of rectal distention in healthy volunteers without modifying rectal resistance. We evaluated whether octreotide has similar effects on rectal perception and resistance in diarrhea-prone IBS patients. Octreotide (100 micrograms s.c.) and placebo were injected in double-blind fashion in eight IBS patients. Rectal balloons measured volumes that evoked increasing levels of perception and intrarectal pressures. After placebo, threshold perception, pressure, urgency and maximal tolerated volume were reported at 18 +/- 5, 46 +/- 8, 72 +/- 7 and 102 +/- 10 ml by the IBS patients, values less than we have observed in healthy volunteers. With octreotide, these sensations were perceived at higher volumes (40 +/- 10, 89 +/- 16, 167 +/- 20 and 202 +/- 25 ml, P < .05) that approximated responses in healthy volunteers. IBS patients exhibited higher rectal pressures at each volume and showed a trend to higher rectal resistance (0.13 +/- 0.02 mmHg/ml) than we have observed in healthy volunteers. These abnormalities were normalized by octreotide. Octreotide did not block the rectoanal inhibitory reflex confirming a lack of effect on local rectal reflex arcs. As with healthy volunteers, IBS patients with diarrhea experience reduced perception of rectal distention after octreotide. Octreotide also reduces elevated rectal pressures in IBS patients, in contrast to healthy volunteers. Thus, octreotide shows potential therapeutic benefit in IBS via dual effects on visceral afferent pathways and rectal wall stiffness.