Editing Flatulence (section)

==Signs and symptoms==

Generally speaking, there are four different types of complaints that relate to intestinal gas, which may present individually or in combination.

===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.

===Excessive volume===
The range of volumes of flatus in normal individuals varies hugely (476–1,491&thinsp;mL/24&thinsp;h).<ref name="Tangerman 2009" /> All intestinal gas is either swallowed environmental air, present intrinsically in foods and beverages, or the result of gut fermentation.

Swallowing small amounts of air occurs while eating and drinking. This is emitted from the mouth by eructation (burping) and is normal. Excessive swallowing of environmental air is called [[aerophagia]], and has been shown in a few case reports to be responsible for increased flatus volume. This is, however, considered a rare cause of increased flatus volume. Gases contained in food and beverages are likewise emitted largely through eructation, e.g., carbonated beverages.

Endogenously produced intestinal gases make up 74 percent of flatus in normal subjects. The volume of gas produced is partially dependent upon the composition of the intestinal microbiota, which is normally very resistant to change, but is also very different in different individuals. Some patients are predisposed to increased endogenous gas production by virtue of their gut microbiota composition.<ref name="Azpiroz 2005" /> The greatest concentration of gut bacteria is in the colon, while the small intestine is normally nearly sterile. Fermentation occurs when unabsorbed food residues arrive in the colon.

Therefore, even more than the composition of the microbiota, diet is the primary factor that dictates the volume of flatus produced.<ref name="Azpiroz 2005" /> Diets that aim to reduce the amount of undigested fermentable food residues arriving in the colon have been shown to significantly reduce the volume of flatus produced. Again, increased volume of intestinal gas will not cause bloating and pain in normal subjects. Abnormal intestinal gas dynamics will create pain, distension, and bloating, regardless of whether there is high or low total flatus volume.

===Odor===
Although flatus possesses an odor, this may be abnormally increased in some patients and cause social distress to the patient. Increased odor of flatus presents a distinct clinical issue from other complaints related to intestinal gas.<ref name="Bailey 2009">{{cite journal |last=Bailey |first=J |author2=Carter, NJ |author3=Neher, JO |title=FPIN's Clinical Inquiries: Effective management of flatulence |journal=[[American Family Physician]] |date=June 15, 2009 |volume=79 |issue=12 |pages=1098–100 |pmid=19530642}}</ref> Some patients may exhibit over-sensitivity to bad flatus odor, and in extreme forms, [[olfactory reference syndrome]] may be diagnosed. Recent informal research found a correlation between flatus odor and both loudness and humidity content.<ref>{{cite web|last=Brain|first=Monkey|date=October 8, 2020|title=Bimodal Farts|url=https://flatology.com/bimodal-farts/|website=The Invisible College of Experimental Flatology}}</ref>

===Incontinence of flatus===
"Gas incontinence" could be defined as loss of voluntary control over the passage of flatus. It is a recognised subtype of [[faecal incontinence]], and is usually related to minor disruptions of the continence mechanisms. Some consider gas incontinence to be the first, sometimes only, symptom of faecal incontinence.<ref name="ASCRS textbook">{{citation |editor=Bruce G. Wolff |editor2=James W. Fleshman |editor3=David E. Beck |editor4=John H. Pemberton |editor5=Steven D. Wexner |title=The ASCRS textbook of colon and rectal surgery |year=2007 |publisher=[[Springer Publishing]] |location=New York |isbn=978-0-387-24846-2}}</ref>