Bloating and Distension in Irritable Bowel Syndrome: The Role of Gastrointestinal Transit

OBJECTIVES: Patients with irritable bowel syndrome and constipation (IBS-C) show more abdominal distension than do those with diarrhea. Because constipation is often associated with delayed gastrointestinal transit, this study aimed at establishing whether patients with delayed transit show more distension and bloating than do those with normal transit. METHODS: Abdominal girth was recorded for 24 h using abdominal inductance plethysmography (AIP) in 30 IBS-C (Rome II criteria) patients (aged 18-68 years; 27 women) and in 30 healthy volunteers (21-58 years of age; 26 women). Within 2 weeks of this recording, orocecal and colonic transits were assessed. Orocecal transit was determined from the increase in breath hydrogen after a standard meal, and colonic transit from the number of radio-opaque markers identified on a plain abdominal X-ray. Bloating severity was assessed hourly during AIP recording using a 0-5 scale. RESULTS: IBS-C patients showed more bloating and distension than did healthy volunteers (P<0.001). They also had prolonged colonic (P<0.001) and orocecal (P=0.05) transits than did healthy volunteers, such that 47 and 17%, respectively, had colonic and orocecal transit times greater than the normal reference range. Those with delayed colonic (P=0.025) and orocecal (P=0.13) transits had greater distension but not bloating (P=0.63 and P=0.48, respectively) compared with those with normal transit. Moreover, distension directly correlated with orocecal (r=0.40;P=0.03) and colonic (r=0.51; P=0.004) transit times and inversely with stool consistency (r=-0.43; P=0.07). CONCLUSIONS: IBS-C patients with delayed transit show greater abdominal distension than do those with normal transit. Therefore, drugs that accelerate transit may be expected to alleviate this troublesome problem.