Objectives: Abdominal bloating and distension are common symptoms of irritable bowel syndrome (IBS). The postulated pathophysiological mechanisms underlying these symptoms include increased production, retention, or perception of gas or luminal contents. The aims of this study were to prospectively compare the prevalence of, and clinical factors related to, bloating and distension in an IBS patient population.
Methods: A total of 714 consecutive patients who met Rome I criteria for IBS were prospectively surveyed, and were classified as having bloating alone (B) or bloating and distension (B+D) based on a comprehensive bowel symptom questionnaire. GI, extraintestinal, and psychological symptoms, as well as health-related quality of life measures were also assessed using validated survey instruments.
Results: A total of 542 IBS patients (76%) who reported abdominal bloating were studied. Of these, 132 patients fulfilled criteria for the B group, whereas 410 patients fulfilled criteria for the B+D group. There was a significantly different gender distribution in the B and B+D groups (female:male ratios, 1.4:1 and 2.8:1, respectively p < 0.02). There was also a significantly different bowel habit subgroup distribution, with a greater predominance of constipation in B+D group and of diarrhea in the B group (p < 0.03). Both groups were similar in other clinical parameters, including progressive worsening of symptoms during the day, and relief by passing stool or gas. Both bloating and distension worsened when other abdominal symptoms worsened. Abdominal distension was associated with greater symptom severity and less diurnal variation in symptoms, and was less often perceived as associated with food intake.
Conclusions: Bloating and visible abdominal distension may arise from two distinct but interrelated physiological processes. Although the sensation of bloating may be related to enhanced sensitivity to visceral afferent stimulation, abdominal distension in more severely affected patients may be related to triggering of a visceromotor reflex affecting the tone of abdominal wall muscles.