Although the terms bloating and distension often are used synonymously, evidence now suggests that these are distinct conditions that may overlap but do not necessarily coexist, as discussed in a recently published review by Lesley Houghton, MD, and colleagues in Neurogastroenterology and Motility. The authors provide support for defining abdominal bloating as a subjective sensation and distension as a physical parameter that refers to an actual increase in abdominal girth. They note that bloating accompanied by visible distension is more common in patients with irritable bowel syndrome (IBS) than in healthy participants. The underlying cause of these symptoms remains unclear.
Novel studies suggest that IBS patients may process gas abnormally, even in the absence of excessive production. Furthermore, patients with constipation retain more gas than those with diarrhea, suggesting that processing of gas may be related to differences in gastrointestinal (GI) motility. IBS patients also have been shown to have lower sensory thresholds than healthy individuals. Clinical studies with tegaserod, a 5-HT4 receptor agonist, have demonstrated significant reductions in bloating in patients with IBS with constipation and chronic constipation. These studies suggest that bloating and distension, at least in some individuals, may be related to impaired GI motility, altered visceral sensation, or both.