Flatulence (gas)

• Definition
• Causes
• Assessment
• Treatment

Flatulence refers to the passage of gastrointestinal gas (flatus) under pressure via the rectum and anus (back passage). In colloquial terms this is referred to as ‘farting.’ Excess gastrointestinal gas is most commonly caused by air-swallowing (aerophagia) which occurs in patients who ingest food too quickly or are overly anxious. Rarely flatulence may be secondary to a serious underlying gastrointestinal disorder so it is worth having this symptom investigated by a doctor. In addition, flatulence can be a potentially embarrassing disorder and be quite socially disabling for patients. Management concentrates on lifestyle measures as drug treatments have shown little benefit to date.

Definition

Flatulence is the release of a mixture of gases (flatus) from the rectum under pressure. Flatus consists of methane, nitrogen, hydrogen and carbon dioxide gases and is often accompanied by a sound and smell. The ratio of the constituent gases varies depending on your diet which subsequently alters the odour of the flatus. Normally flatus is passed 10-20 times per day, equating to 400-1300 mL of gas passed via the rectum. However, the normal amounts of flatus varies largely between people so it is more important to take note of changes in the amount and other associated symptoms such as belching (which is the passage of gastrointestinal gas via the mouth, commonly referred to as ‘burping’) and abdominal bloating.

You may therefore notice you have flatulence due to the following symptoms:

• Passing wind often
• Smelly flatus
• Loud flatus
• Abdominal distension and discomfort
• Rumblings in the lower abdomen.

Causes

Production of intestinal gas is a normal part of the digestive process caused by reactions of enzymes and the breakdown of food by bacteria. Normally most of this gas produced will be reabsorbed and enter the bloodstream. However, if a large amount is produced it will remain in the intestines and travel along to be later expelled. The following conditions may lead to an increase in gas expulsion:

• Air swallowing- A small amount of air is normally swallowed when you eat or drink. If you eat quickly, gulp foods, drink through straws or chew gum you may swallow increases amounts of gas. In addition, anxiety can cause excessive air swallowing. Air swallowing is the most common cause of flatulence.
• High-fibre diets- Fibre is difficult to breakdown in the intestine. This leads to bacteria in the colon working overtime to further digest food. These bacteria are one of the key sources of gas leading to flatulence. Common high fibre foods such as bread, are imaged below.
  
• Irritable bowel syndrome– Patients with this disorder have alternating episodes of constipation and diarrhoea which are often accompanied by flatulence and bloating.
• Lactose intolerance– Inability to absorb the sugars present in milk leads to gas production as these have to be broken down by bacteria via the process of fermentation. Dairy foods such as milk, cheese and cream (displayed below) can exacerbate symptoms as they contain a high concentration of lactose.
  
• Medications- Some antibiotics and other drugs can cause flatulence.
  
• Rarely flatulence may be a symptom of a serious underlying disease such as coeliac disease or pancreatic insufficiency which can lead to malnutrition

Assessment

Your doctor will take a thorough history to determine the likely cause of your symptoms. This will include questions such as:

• What is your diet like?
• Any recent changes to your diet (particularly an increase in fibre)?
• How fast do you normally eat, chew and swallow your food?
• How severe are your symptoms? Do they impact on your daily life?
• Does your gas seem to be related to eating milk products or other specific foods?
• Are you taking any current medications?
• Do you have other symptoms?

Following this your doctor will carefully exmine you focussing on the abdomen for any signs of abnromality. Occasionally further tests may be ordered such as endoscopy (can help find ulcers or reflux), blood tests, sigmoidoscopy or colonoscopy, barium enema and so on, to identify possible causes.

Treatment

Management of excessive gas can be quite difficult and does not always work in all patients. You can help relieve this symptom by adopting the following lifestyle measures:

• Eat more slowly.
• Chew your food thoroughly.
• Relax whilst you eat.
• Avoid carbonated drinks and chewing gum.
• Limit foods associated with large amounts of flatus such as legumes, beans, lentils, raisins, foods high in insoluble fibre, artificial sweeteners and vegetables of the cabbage family.
• Quit smoking.
• Reduce milk consumption if lactose intolerance has been identified as the problem.
• Add probiotics (such as yoghurt) to your diet to replenish the normal good bacteria in the bowel.

Relaxation techniques have been shown to be helpful. Unfortunately the medical treatments currently available such as simethicone, antacids, activated charcoal and beano have failed to produce favourable results.

References

1. Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine. 15th Edition. McGraw-Hill. 2001.
2. Price KR, Lewis J, Wyatt GM, Fenwick GR. Flatulence – causes, relation to diet and remedies. Molecular Nutrition and Food Research. 2006; 32(6): 609-26.
3. Kumar, Clark. Clinical Medicine. 5th Edition. Saunders. 2002.
4. Longmore, Wilkinson, Rajagopalan. Oxford Handbook of Clinical Medicine. 6th Edition. Oxford University Press. 2004.
5. Medline Plus- Medical Encyclopedia. Gas- Flatulence. US National Library of Medicine, 2004. Available [online] at URL: http://www.nlm.nih.gov/medlineplus/ency/article/003124.htm
6. Szarka L, Levitt M. Belching, bloating and flatulence. American College of Gastroenterology. 2006. Available [online] at URL: http://www.acg.gi.org/patients/gihealth/belching.asp