Abdominal bloating is felt by patients as a feeling of fullness, tightness or distension in the abdomen. Bloating is different to abdominal swelling, where the abdomen is actually increased in size, although both of these features may be present.
Abdominal bloating is quite common and in the majority of cases will not be caused by anything serious. Excessive gas due to dietary factors, irritable bowel syndrome (IBS) or difficulty absorbing certain foods are amongst the most common causes. If your abdominal bloating is prolonged, severe, or if you have other worrying symptoms (e.g. diarrhoea, constipation, weight loss or bleeding) it is extrememly important you see your doctor so they can exclude serious conditions (e.g. cancer).
Abdominal bloating refers to a sensation of fullness or a sense of abdominal enlargement. It is often due to disturbance in the normal function of the gastrointestinal tract, causing an increase in intestinal gas.
Gas in the intestine is a mixture of numerous different components which can be increased by swallowing too much air, excess production, or impaired absorption due to obstruction. Excess gas causes bloating as well as other gas symptoms such as flatulence or burping.
If the abdomen is visibly distended in association with bloating, it is more likely that there is an organic, rather than functional, cause of the symptom. Bloating is frequently associated with abdominal pain that may be relieved by passing gas or bowel motions.
Abdominal bloating may be a feature of a number of disorders, the majority of which are not serious and result from changes in gastrointestinal function. Possible common causes are:
Your body takes a long time to break down and expel fat from the body. Too much fat in your diet can cause episodes of bloating. Other foods can cause bloating due to the formation of extra gas. These foods include cabbage, cauliflower, baked beans and salads.
A number of disorders exist where the body cannot break down and absorb certain components of food. In these cases, the remaining food products can produce extra gas due to certain chemical reactions, or due to the good bacteria in the bowel trying extra hard to break these foods down. Lactose intolerance, coeliac disease and other food intolerances are examples of disorders that cause bloating by these mechanisms.
If you swallow large amounts of air, your bowel has trouble absorbing or removing it all from the body fast enough. This means more will stay within the bowel lumen and cause the sensation of a full bowel. Anxiety or nervousness, eating quickly, gulping food or beverages, drinking through straws and chewing gum can all cause you to swallow increased amounts of air.
Irritable bowel syndrome
Irritable bowel syndrome is a common disorder where patients have alternating episodes of constipation and diarrhoea. Abdominal bloating is one of the key features of this diagnosis.
Partial bowel obstruction
A blockage at some point in the intestines will impair the mechanical transit of food and may lead to bloating.
Constipation is characterised by a reduction in the frequency of bowel motions, and may cause bloating.
Very rarely, your bloating may be due to a more serious condition, so it often pays to discuss your symptoms with a doctor. The following conditions are less common but don’t want to be missed:
- Ascites: Sometimes you may feel bloated due to the accumulation of fluid within the abdominal cavity, called ascites. This is often the result of liver disease.
- Tumours: Very occasionally, you may feel bloated because there is a tumour present within your abdomen, of the ovaries, liver, stomach or elsewhere. The present of a lump or swelling should alert you to the possibility of a tumour or cancer.
- Infection: Certain parasitic disorders can cause abnormal dilatations of the colon (megacolon) associated with symptoms of bloating.
If you experience abdominal bloating, it is important to see your doctor to make sure there is nothing serious present. In particular, if you have symptoms of diarrhoea, constipation, weight loss or bleeding from anywhere in the gastrointestinal tract (vomiting blood or bloody or dark stools), there is a greater possibility that something more serious is present rather than just a functional problem.
When you see your doctor, you should be prepared to answer detailed questions about:
- Duration of the bloating
- Your diet
- The relationship of the bloating to certain foods
- If you’re a female, any change in bloating during the menstrual cycle
- Any other associated symptoms
- Any past medical history
- Current medications
Your doctor will then examine you, paying particular attention to palpating your abdomen for any masses or swelling. Your doctor will also tap your belly to identify any fluid present. Listening to bowel sounds can help your doctor determine if there is an obstruction. The doctor may perform a rectal examination if you have other bowel symptoms.
If your bloating is due to a functional problem, such as an inability to tolerate dairy products or wheat, examination is likely to be normal. Your doctor may suggest trials of certain diets to determine if it is a particular food triggering your symptoms.
Investigations are needed in some patients, particularly when the other serious symptoms are present. Your doctor may refer you for the following:
- Radiography: Plain x-rays of your abdomen can tell if it is blocked in certain places.
- Ultrasound or CT scans: May be done if the doctor suspects ascites (fluids) or a mass.
- Colonoscopy: Involves inserting a long tube (with a light and a camera on the end of it) into the rectum (back passage). The doctor can then look at the inside of the bowels to make sure there are no tumours (e.g. colon cancer).
- Barium enema
If a specific cause is suggested (e.g. lactose intolerance), special trial diets or further diagnostic testing (e.g. lactose tolerance test) may be required. Coeliac disease may be diagnosed by a series of blood tests looking for certain antibodies.
The treatment of bloating mainly depends on the underlying cause of the symptom. Your doctor would have performed a number of necessary tests to exclude serious problems. Treatment then focuses on a number of diet and lifestyle changes:
- Avoid carbonated beverages.
- Avoid chewing gum as this predisposes to air swallowing.
- Avoid foods that are difficult to digest or that cause increased amounts of gas (e.g. brussel sprouts, cabbage, beans and lentils).
- Be careful of your sources of fibre. Patients with IBS often need increased amounts of fibre to relieve their symptoms, however, some types of fibre such as psyllium (in Metamucil) can exacerbate bloating. You should discuss your choice of fibre supplements with a pharmacist.
- Eat small, frequent meals at a reasonable pace (slowly).
- Drinking fennel tea may help your symptoms.
In some patients, over-the-counter medications such as simethicone, beano and activated charcoal can help gas symptoms. Your doctor may suggest a trial of some of these, but unfortunately they have only modest benefits and do not work in all patients.
For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
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