4 Belching, Bloating, and Flatulence
Belching is not a symptom of organic disease. The only cause of belching is the swallowing of air (aerophagia). Air is swallowed or, more accurately, sucked into the stomach and released in the form of a belch. Air swallowing may occur with eating or drinking; more air is swallowed with liquids than with solids. Aerophagia also occurs as a conscious or, more often, an unconscious nervous habit unassociated with food ingestion. It can also be associated with mouth breathing, gum chewing, orthodontic appliances, and poorly fitting dentures. Chronic, repetitive, unintentional belching is usually caused by repetitive inhalation of air and its regurgitation from the stomach or esophagus in the form of a belch. Some patients who demonstrate these findings consciously or unconsciously relax the upper esophageal sphincter during inspiration. Belching occurs in patients with dyspepsia and may be an uncommon sign of gastroesophageal reflux. It cannot be used to differentiate between them.
Excessive belchers tend to be nervous, anxious, and tense. Belching is often normal in infants, although excessive belching may be the result of excessive air swallowing during feeding. If the seal of the infant’s lips is inadequate around the real or artificial nipple, air may be ingested during nursing. This may be exaggerated if during feeding the child is held in a position that is too horizontal.
Some patients with gastric or biliary disorders develop a habit of trying to relieve abdominal discomfort by swallowing (sometimes unconsciously) air and belching it up again; they believe that this provides some relief from their abdominal discomfort.
If associated pathology can be confidently ruled out, patients must be reassured that nothing serious is wrong. It may help to describe how a patient with a laryngectomy can be trained to swallow air; accordingly, a patient with a belching problem can be untrained. Simply instructing some patients not to belch when they feel the urge to do so may gradually stop their habit of swallowing air and belching it back. Antifoaming agents have not been particularly helpful. Instead, patients should be instructed to avoid chewing gum, eating quickly, smoking, and drinking carbonated beverages.
The most common associated symptom is abdominal distention, representing gas in the stomach. Most swallowed air that is not belched up is reabsorbed in the small intestine. Usually, intestinal gas is derived by fermentation of intestinal contents. Some patients who swallow large amounts of air may experience or perceive abdominal discomfort until they belch. An urge to belch accompanied by chest pain on belching is a rare finding that may indicate an inferior wall myocardial infarction.
The most common precipitating factor is air swallowing and subsequent relaxation of the esophageal sphincter to produce a belch. Nervous concern about belching can initiate a vicious circle of unconscious air swallowing and more belching. For some individuals, a supine position prevents swallowed gastric air from escaping into the esophagus, and an upright position facilitates belching. Emotional stress increases the likelihood of air swallowing. Ingestion of carbonated beverages, gum chewing, and poorly fitting dentures may also aggravate belching.
Although belching is invariably caused by swallowing air, this fact does not rule out coexisting unrelated pathology. If other symptoms warrant further tests, cholecystography, upper gastrointestinal (GI) studies, and chest radiography should be considered.
Oral eructation of intestinal gas rarely occurs. In patients with this condition, the odor is offensive, resembling that of methane or hydrogen sulfide. It suggests fermentation in stagnating gastric contents secondary to gastroparesis, vagotomy, or pyloric obstruction from an ulcer or tumor.
Bloating and flatulence are two common complaints reported to physicians. The problem has been recognized since the time of Hippocrates, who taught that “passing gas is necessary to well-being.” In the days of early Rome, it was noted that “all Roman citizens shall be allowed to pass gas whenever necessary.” Because swallowed air is reabsorbed in the small bowel, most of the gas in the distal small bowel and colon is produced within the bowel by fermentation. Small-bowel bacterial overgrowth can lead to malabsorption syndrome characterized by flatulence, diarrhea, chronic abdominal pain, and bloating; symptoms are often seen in patients with irritable bowel syndrome. In most instances, flatulence is not of any clinical significance, but because various pathologic conditions may be associated with it, their presence should be investigated if the flatulence is excessive.
Bloating may be caused by gaseous distention of the stomach, small bowel, or colon. This condition occurs more frequently in patients with gastroparesis, malabsorption of various sugars and fat, and colonic bacterial fermentation of unabsorbed foods. In some patients, disturbed visceral motility and increased sensitivity to normal luminal distention may cause the sensation of bloating.
Flatulence is usually caused by excessive production of gas (in the large bowel and less frequently in the small bowel) in an otherwise normal individual or increased discomfort from normal amounts of abdominal gas in healthy individuals. If bloating and flatulence have persisted for several years without the development of signs of serious organic pathology (e.g., weight loss, ascites, jaundice), the patient can be reassured that the flatulence is not of great clinical significance. However, it must always be remembered that some patients with gallbladder disease, colon carcinoma, irritable bowel syndrome, diverticulitis, and diverticulosis may present with a chief complaint of abdominal discomfort, bloating, and, occasionally, flatulence. Patients with colon carcinoma may present with vague abdominal discomfort or distention.
Flatulence is particularly common in infants up to age 3 months. This condition, referred to as 3-month colic, is caused by immature nervous control of the gut, which permits gas to become trapped in bowel loops.
Malabsorption may lead to excessive fermentation of unabsorbed nutrients; this may produce an increase in flatulence. It can occur in patients with pancreatic insufficiency, pancreatic carcinoma, biliary disease, celiac disease, or bacterial overgrowth in the small intestine.
Native Americans and other patients, particularly of African or Mediterranean descent, who complain of excessive bloating or flatulence may have malabsorption and subsequent fermentation due to lactose intolerance. Lactose intolerance does not usually occur in infants or preschool children unless a lactase deficiency develops secondary to other disorders, such as bacterial or viral infections of the small bowel, giardiasis, or sensitivity to cow’s milk or gluten (celiac disease). This diagnosis is confirmed if diarrhea develops or if the bloating or flatulence is exacerbated after ingestion of a lactose load (found in milk, ice cream, and other dairy products).