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Bacterial Overgrowth Syndrome

Bacterial Overgrowth Syndrome

Excessive belching, abdominal bloating, and flatulence caused an 89-year-old woman to seek medical attention. She reported that these previously mild and intermittent symptoms of 20 years’ duration had worsened during the last 2 years. Because of the patient’s history of anxiety, the GI symptoms had been attributed to anxiety-induced aerophagia. The medical history also included depression, early-stage macular degeneration, and Alzheimer’s dementia. There was no nausea, vomiting, early satiety, diarrhea, or weight loss. The patient was taking vitamin E, donepezil, and paroxetine. She had no allergies. Despite the constant burping, the patient was in no distress. Her short-term memory was poor, and central vision in both eyes was decreased. Examination findings were unremarkable; the abdomen was normal. Rectal sphincter tone was good; stools were brown and heme-negative. An upper GI series revealed a 3-cm duodenal diverticulum with multiple small intestinal diverticula. Diverticula are potential sources of bacterial overgrowth. Excessive bacterial fermentation of carbohydrates causes increased gas production. A breath test showed abnormally high levels of hydrogen. Drs Mubashir Shah, Khalid Aziz, and Joel Levine of Farmington, Conn, diagnosed bacterial overgrowth syndrome with excessive gas production. The patient was given antibiotics, and her symptoms resolved. The sole source of hydrogen in the gut is the bacterial metabolism of exogenous fermentable substances, such as undigested oligosaccharides from fruits and vegetables— particularly legumes—and incompletely digested polysaccharides from wheat, oats, potatoes, and corn.1 Hydrogen-producing bacteria are normally limited to the colon; however, patients who have severe bacterial overgrowth syndromes produce hydrogen in the small bowel as well as the colon. Persons with intestinal disorders who cannot completely absorb carbohydrates and proteins also produce increased amounts of colonic hydrogen.2 Fecal bacteria produce hydrogen during fermentation of mucoproteins. The high fasting hydrogen excretion observed in some persons with bacterial overgrowth of the small bowel or untreated celiac sprue has been attributed to the increased availability of mucus.3,4 Chronic belching usually is a functional disorder. Patients under emotional stress or those who have thoracic or abdominal discomfort from any cause may complain of frequent, involuntary belching. Belching apparently transiently relieves the patient’s distress. However, if some of the swallowed air enters the stomach and intestines, discomfort may occur and a vicious cycle can develop. Reserve radiographic evaluation and laboratory studies for patients who have additional complaints that suggest thoracic or abdominal pathology. If no associated disease is present, counsel the patient and thoroughly explain the aerophagia-belching mechanism. This knowledge can break the vicious cycle; although belching may continue, distress is diminished when the benign origin of their eructation is understood. Recommend that patients chew rather than gulp food, eat and drink slowly, and avoid chewing gum.

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