Involuntary postprandial belching
Magenblase syndrome
Aerophagia (e.g. from gum chewing, smoking, oral irritation)
Gastroesophageal reflux
Biliary colic

Bacterial overgrowth
Intestinal or colonic obstruction
Diverticula of the small intestine
Hypochlorhydria
Chronic intestinal pseudo-obstruction
Cologastric fistula
Coprophagia

Functional bowel disorders
Irritable bowel syndrome
Nonulcer dyspepsia
Idiopathic constipation
Functional diarrhea

Carbohydrate malabsorption
Lactase deficiency
Fructose, sorbitol, and starch intolerance
Bean and legume ingestion

Gas-bloat syndrome
Postfundoplication

Miscellaneous causes
Hypothyroidism
Medications (e.g. anticholinergics, opiates, calcium channel antagonists, antidepressants)

Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth may result from mechanical obstruction of the gut from postoperative adhesions, Crohn’s disease, radiation enteritis, ulcer disease, or malignancy. Other organic abnormalities that predispose to bacterial overgrowth include small intestinal diverticula and gastric achlorhydria. Motor disorders of the gut are associated with overgrowth because of an impaired ability to clear organisms from the gut; 43% of cases of diabetic diarrhea are attributable to bacterial overgrowth. Disorders that increase bacterial delivery to the upper gut (e.g. cologastric fistulae and coprophagia) can overwhelm normal defenses against infection.

Dysmotility syndromes

Conditions that alter gut motor function produce prominent gas and bloating. Bloating is reported by patients with gastroparesis and by those with fat intolerance and rapid gastric emptying. A consequence of fundoplication for gastroesophageal reflux disease is an inability to belch or vomit secondary to an unyielding wrap of gastric tissue around the distal esophagus. In the initial months after fundoplication, up to 70% of patients experience bloating, upper abdominal cramping, and flatulence, a constellation of symptoms known as gas-bloat syndrome. Intestinal pseudo-obstruction leads to gaseous symptoms because of delayed small bowel transit of gas and development of bacterial overgrowth. Bloating also is reported by patients with chronic constipation.

Functional bowel disorders

Irritable bowel syndrome and functional dyspepsia may manifest with symptoms of gas and bloating. The pathogenesis is likely multifactorial and although some studies illustrate increased gas production and objective abdominal distension in irritable bowel syndrome, others do not. Abnormal gut motor and sensory function contribute to the symptoms of gas and bloating.

Miscellaneous causes

Aerophagia during gum chewing, smoking, or oral irritation produces significant gas symptoms, especially eructation. Patients who have undergone laryngectomy experience eructation from swallowing air for esophageal speech. Patients with intestinal obstructions may infrequently present only with symptoms of gas and bloating. Small bowel malabsorptive conditions including celiac disease may produce gaseous manifestations that may predominate or be part of a larger constellation of symptoms. Individuals with peptic ulcer, gastroesophageal reflux, or biliary colic may belch to relieve their other symptoms. Gaseous complaints may be reported as consequences of endocrinopathies such as hypothyroidism. Many medications (e.g. anticholinergics, opiates, calcium channel antagonists, and antidepressants) produce gas by retarding gut transit.