Bloating and Distension in Functional GI Disorders

Although the terms bloating and distensionoften are used synonymously, evidence nowsuggests that these are distinct conditions thatmay overlap but do not necessarily coexist, asdiscussed in a recently published review byLesley Houghton, MD, and colleagues in Neurogastroenterologyand Motility. The authorsprovide support for defining abdominal bloatingas a subjective sensation and distensionas a physical parameter that refers to an actualincrease in abdominal girth. They note thatbloating accompanied by visible distension ismore common in patients with irritable bowelsyndrome (IBS) than in healthy participants.The underlying cause of these symptomsremains unclear.

Novel studies suggest that IBS patientsmay process gas abnormally, even in theabsence of excessive production. Furthermore,patients with constipation retain moregas than those with diarrhea, suggesting thatprocessing of gas may be related to differencesin gastrointestinal (GI) motility. IBSpatients also have been shown to have lowersensory thresholds than healthy individuals.Clinical studies with tegaserod, a 5-HT⁴ receptoragonist, have demonstrated significantreductions in bloating in patients with IBS withconstipation and chronic constipation. Thesestudies suggest that bloating and distension,at least in some individuals, may be related toimpaired GI motility, altered visceral sensation,or both.