Excessive Gas

Introduction

Gastrointestinal (GI) gas comes in two forms, that from the upper GI tract and that from the lower GI tract.  Though the gases from each location are different in chemical composition, the path gas takes through the GI tract is really one of a continuum, being modified by the gut and bowel flora along the way.  Only occasionally does excessive gas indicate significant disease, usually in clinically apparent scenarios.  Most of the time it is associated with benign conditions.

Stomach gas usually arises from swallowing air during eating, particularly while eating quickly or gulping.  Chewing gum and smoking can also increase stomach gas.  The composition is mostly N2 and O2, the composition of air.   Stomach gas may pass retrograde through the esophagus and mouth, leading to a belch or eructation.  Alternatively it may pass into the small intestine, where gut bacteria begin to exert effects on nutrients as well as the gas itself.  This changes the chemical composition of the gas.

In the small and large bowel, CO2, H2, and methane, in addition to N2 and O2, become the major constituents of intestinal gas.  These arise from digestion of nutrients, bacterial fermentation of gut contents, and other chemical reactions that occur in the bowel lumen.  These gases do not possess odor.  The odor of flatus comes from components in much lesser concentrations, such as sulfur-containing compounds, short-chain fatty acids, ammonia, and others. 

Most of the time, excessive gas is related to dietary practices and specific foods.  In certain situations flatus may be related to antibiotics, which alter the balance of bowel flora, malabsorption syndromes, bowel obstruction and bacterial overgrowth, other bowel infections, motility disorders, and psychiatric conditions.  Abdominal distension is a common co-complaint of excessive gas even though studies indicate the amounts of intestinal gas are similar in those that do and do not complain of associated distension.

History

Determine the dietary practices of the patient:

• What foods are commonly eaten and which seem to be associated with excessive gas?  
• How rapidly are meals eaten?  
• Does the patient gulp food? 
• Does the patient smoke or chew gum regularly?  
• Is there associated acid reflux or emesis, indicating possible GERD or motility problems?  
• In those patients who are lactose intolerant, dairy products often lead to exacerbation of symptoms along with abdominal cramping and bloating. A
• ssess for the possibility of malabsorption and/or inflammatory bowel disease.  
• Are there abnormal bowel movements, foul or greasy stools that are difficult to flush, bloody bowel movements, weight loss, fevers, night sweats? 

Ask about previous bowel procedures or surgeries:

• Could obstruction or adhesions be present?  

What medications is the patient taking and are any associated with increased gas production?  

Ask about camping in the past and drink mountain water since Giardia infections may present with excessive gas.

Irritable bowel syndrome is a condition of unclear etiology characterized by chronic abdominal pain and altered bowel habits without organic cause

Physical Exam

Examine the abdomen and assess for bowel sounds, areas of tenderness, and mass lesions.  If indicated, do an anal exam looking for fissures or fistulas indicative of Crohn’s disease.  Assess the psychiatric state of the patient for the possibility of anxiety or depression. 

Labs and Other Tests

If available and warranted, consider stool studies for occult blood, stool culture, fecal leukocytes, ova and parasites, or fecal fat (often present in malabsorption or pancreatic insufficiency) as indicated.  If considering bowel obstruction, a flat and upright KUB is warranted.  

Plan

Tailor treatment to the suspected cause.  

• Encourage patients that gulp their food to slow down.  
• Discontinue foods or drinks that aggravate symptoms as well as chewing gum and smoking.  
• Simethicone is a popular treatment of excessive gas and bloating though it has not been proven to be of benefit.  
• Lactose restriction or ingestion of lactase often provides benefit for lactose-intolerant persons.  
• If acid reflux is present, consider antacids or H2-blockers.  
• Consider discontinuing offending medications.  
• If bacterial overgrowth or Giardia infection is suspected, a 2 week course of metronidazole can be tried.  
• If inflammatory bowel disease or malabsorption is suspected, a discussion with a gastroenterologist is indicated since the definitive diagnosis of these conditions involves endoscopy.  
• Bowel obstruction should be discussed with a gastroenterologist or general surgeon with plans for possible medevac.  If bowel obstruction is present, bowel decompression with a nasogastric tube should be performed.   
• If anxiety, depression, or irritable bowel syndrome is the etiology, then reassurance, education, and other counseling are appropriate.  
• In addition to dietary modification and behavioral therapy, several medical treatments have been used for irritable bowel syndrome including bulking agents, anti-cholinergic agents (dicyclomine, hyoscyamine), and anti-depressants.

This section provided by LT Arthur S. Pemberton, MC, USNR

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*This web version is provided by The Brookside Associates, LLC.  It contains original contents from the official US Navy NAVMED P-5139, but has been reformatted for web access and includes advertising and links that were not present in the original version. The medical information presented was reviewed and felt to be accurate in 2001. Medical knowledge and practice methods may have changed since that time. Some links may no longer be active. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the US Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense.

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