Intrarectal injection of glycerol induces hypersensitivity to rectal distension in healthy subjects without modifying rectal compliance

Background Rectal sensory thresholds are lowered in patients with irritable bowel syndrome (IBS), reflecting visceral hyperlagesia, which might be rel ated to subclinical inflammation. Aim To evaluate the effects of an intraluminal injection of glycerol, a muc osal irritant, on rectal tone and perception of distension in 12 healthy su bjects. Methods Rectal tone was evaluated with a barostat. First sensation, need to defecate and pain thresholds were evaluated during isobaric phasic distens ions, before and 20 and 120 min after injection of 10 mi glycerol in the re ctum. Results Baseline bag volume (97.9 +/- 56.2 ml) significantly decreased 20 m in (49.7 +/- 42.2 mi; P = 0.026) and 120 min (66.5 +/- 38.3 mi; P = 0.050) after injection of glycerol, indicating its hypertonic effect. The pressure defining sensory thresholds was decreased significantly 20 min after glyce rol injection: first sensation, 14.6 +/- 2.9 versus 18.3 +/- 7.2 mm Hg (P = 0.01); need to defecate, 19.6 +/- 3.7 versus 26.0 +/- 6.9 mmHg; pain, 23.8 +/- 4.5 versus 35.6 +/- 9.5 mm Hg (P = 0.001). This effect was maintained for 120 min after injection of glycerol. Slopes of the compliance curves di d not differ before and after injection of glycerol. Conclusions Intraluminal injection of glycerol significantly increases rect al tone and sensitizes healthy volunteers to rectal distension, since they show significantly lower thresholds after glycerol. This could constitute a model of visceral hypersensitivity in healthy volunteers. for J Gastroente rol Hepatol 13:573-580 (C) 2001 Lippincott Williams & Wilkins.