Editing Flatulence (section)

===Bloating and pain===
Patients may complain of bloating as [[abdominal distension]], discomfort and pain from "trapped wind". In the past, functional bowel disorders such as [[irritable bowel syndrome]] that produced symptoms of bloating were attributed to increased production of intestinal gas.

However, three significant pieces of evidence refute this theory. First, in normal subjects, even very high rates of gas infusion into the small intestine (30{{nbsp}}mL/min) is tolerated without complaints of pain or bloating and harmlessly passed as flatus per rectum.<ref name="Azpiroz 2005" /> Secondly, studies aiming to quantify the total volume of gas produced by patients with irritable bowel syndrome (some including gas emitted from the mouth by eructation) have consistently failed to demonstrate increased volumes compared to healthy subjects. The proportion of hydrogen produced may be increased in some patients with irritable bowel syndrome, but this does not affect the total volume.<ref name="King 1998">{{cite journal |last=King |first=TS |author2=Elia, M |author3=Hunter, JO |title=Abnormal colonic fermentation in irritable bowel syndrome |journal=[[The Lancet]] |date=October 10, 1998 |volume=352 |issue=9135 |pages=1187–9 |pmid=9777836 |doi=10.1016/S0140-6736(98)02146-1|s2cid=1750363 }}</ref> Thirdly, the volume of flatus produced by patients with irritable bowel syndrome who have pain and abdominal distension would be tolerated in normal subjects without any complaints of pain.

Patients who complain of bloating frequently can be shown to have objective increases in abdominal girth, often increased throughout the day and then resolving during [[sleep]]. The increase in girth combined with the fact that the total volume of flatus is not increased led to studies aiming to image the distribution of intestinal gas in patients with bloating. They found that gas was not distributed normally in these patients: there was segmental gas pooling and focal distension.<ref name="Azpiroz 2005" /> In conclusion, abdominal distension, pain and bloating symptoms are the result of abnormal intestinal gas dynamics rather than increased flatus production.