gastrointestinal disorders
Gas Related Complaints
Etiology of Gas Related Complaints
There are 3 main gas-related complaints: excessive belching, distention (bloating), and excessive flatus, each with a number of causes ( see Table: Some Causes of Gas-Related Complaints ). Infants 2 to 4 months of age with recurrent crying spells often appear to observers to be in pain, which in the past has been attributed to abdominal cramping or gas and termed colic. However, studies show no increase in H2 production or in mouth-to-cecum transit times in colicky infants. Hence, the cause of infantile Belching (eructation) results from swallowed air or from gas generated by carbonated beverages. Aerophagia occurs normally in small amounts during eating and drinking, but some people unconsciously swallow air repeatedly while eating or smoking and at other times, especially when anxious or in an attempt to induce belching. Excessive salivation increases aerophagia and may be associated with various gastroesophageal (GI) disorders (eg, gastroesophageal reflux disease), ill-fitting dentures, certain drugs, gum chewing, or nausea of any cause. Most swallowed air is eructated. Only a small amount of swallowed air passes into the small bowel; the amount is apparently influenced by position. In an upright person, air is readily belched; in a supine person, air trapped above the stomach fluid tends to be propelled into the duodenum. Excessive eructation may also be voluntary; patients who belch after taking antacids may attribute the relief of symptoms to belching rather than to antacids and may intentionally belch to relieve distress. A rare cause of excessive belching is supragastric belching. In supragastric belching, a rapid entry of air into the esophagus is expelled after tensing the abdomen. It may occur under volition or unconsciously and can severely affect quality of life ( Etiology reference ). Abdominal bloating may occur in isolation or along with other GI symptoms in patients with functional disorders (eg, aerophagia, nonulcer dyspepsia, gastroparesis, irritable bowel syndrome) or organic disorders (eg, ovarian cancer, colon cancer). Gastroparesis (and consequent bloating) also has many nonfunctional causes, the most important of which is autonomic visceral neuropathy due to diabetes; other causes include postviral infection, drugs with anticholinergic properties, and long-term opiate use. However, excessive intestinal gas is not clearly linked to these complaints. In most healthy people, 1 L/hour of gas can be infused into the gut with minimal symptoms. It is likely that many symptoms are incorrectly attributed to “too much gas.” On the other hand, some patients with recurrent GI symptoms often cannot tolerate small quantities of gas: Retrograde colonic distention by balloon inflation or air instillation during colonoscopy often elicits severe discomfort in some patients (eg, those with irritable bowel syndrome) but minimal symptoms in others. Similarly, patients with eating disorders (eg, anorexia nervosa, bulimia) often misperceive and are particularly stressed by symptoms such as bloating. Thus, the basic abnormality in patients with gas-related symptoms may be a hypersensitive intestine. Altered motility may contribute further to symptoms. There is great variability in the quantity and frequency of rectal gas passage. As with stool frequency, people who complain of flatulence often have a misconception of what is normal. The average number of gas passages is about 13 to 21/day. Objectively recording flatus frequency (using a diary kept by the patient) is a first step in evaluation. (First printed in the 14th Edition of THE MANUAL) Flatulence, which can cause great psychosocial distress, is unofficially described according to its salient characteristics: The “slider” (crowded elevator type), which is released slowly and noiselessly, sometimes with devastating effect The open sphincter, or “pooh” type, which is said to be of higher temperature and more aromatic The staccato or drumbeat type, pleasantly passed in privacy The “bark” type (described in a personal communication) is characterized by a sharp exclamatory eruption that effectively interrupts (and often concludes) conversation (aromaticity is not a prominent feature) Rarely, this usually distressing symptom has been turned to advantage, as with a Frenchman referred to as “Le Petomane,” who became affluent as an effluent performer who played tunes with the gas from his rectum on the Moulin Rouge stage. Flatus is a metabolic byproduct of intestinal bacteria; almost none originates from swallowed air or back-diffusion of gases (primarily nitrogen) from the bloodstream. Bacterial metabolism yields significant volumes of hydrogen, methane, and carbon dioxide. Hydrogenis produced in large quantities in patients with malabsorption syndromes and after ingestion of certain fruits and vegetables containing indigestible carbohydrates (eg, baked beans), sugars (eg, fructose), or sugar alcohols (eg,sorbitol). In patients with disaccharidase deficiencies (most commonlylactasedeficiency), large amounts of disaccharides pass into the colon and are fermented to hydrogen. Celiac disease, tropical sprue, pancreatic insufficiency, and other causes of carbohydrate malabsorption should also be considered in cases of excess colonic gas. Methaneis also produced by colonic bacterial metabolism of the same foods (eg, dietary fiber). However, about 10% of people have bacteria that produce methane but not hydrogen. Carbon dioxideis also produced by bacterial metabolism and generated in the reaction of bicarbonate and hydrogen ions. Hydrogen ions may come from gastric hydrochloric acid or from fatty acids released during digestion of fats—the latter sometimes produces several hundred mEq of hydrogen ions. The acid products released by bacterial fermentation of unabsorbed carbohydrates in the colon may also react with bicarbonate to produce carbon dioxide. Although bloating may occasionally occur, the rapid diffusion of carbon dioxide into the blood generally prevents distention. Diet accounts for much of the variation in flatus production among individuals, but poorly understood factors (eg, differences in colonic flora and motility) may also play a role. Despite the flammable nature of the hydrogen and methane in flatulence, working near open flames is not hazardous. However, gas explosion, even with fatal outcome, has been reported during jejunal and colonic surgery and colonoscopy, when diathermy was used during procedures in patients with incomplete bowel cleaning. 1.Koukias N, Woodland P, Yazaki E, Sifrim D: Supragastric belching: Prevalence and association with gastroesophageal reflux disease and esophageal hypomotility.J Neurogastroenterol Motil21(3):398–403, 2015. doi: 10.5056/jnm15002 