Diagnosing Gas In The Intestinal Tract

Gas Is Most Often Caused By Eating Gassy Foods Or Swallowing Air

Doctor testing stomach of young woman
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Gas in the intestinal tract is normal, and everyone passes a certain amount of gas in the form of flatulence or belching. Most often, gas is a product of eating certain foods or from swallowing air. Many people think they pass too much gas, when the amount that they have is actually normal. However, in some cases, excessive gas might truly need further investigation.

Seeing Your Doctor About Excess Gas

If you think you're having too much gas, you'll want to see your primary physician.
On the first visit to a physician about the problem of excess gas, being able to describe symptoms in detail will help in narrowing down the cause. Some questions a physician might ask about gas are:
  • Are you experiencing belching, or is it flatulence?
  • Is there a change in how much gas you have?
  • Has the odor of your gas changed?
  • Are you experiencing actual belching or flatulence, or more bloating or a feeling of being full?

If your physician is unable to determine the cause of your problems with gas, you might be referred to a gastroenterologist for further evaluation.

Tests To Evaluate Gas

Some tests that might be done to further determine what is causing excess gas or bloating include:
  • Abdominal X-Ray: An x-ray of the abdomen will show if there is any gas in the intestinal tract, as well as its location. Both of these pieces of information will help your physician to make a diagnosis.
  • Upper GI Series: This test is done with barium, and can illuminate any problems in the small intestine.
  • CT Scan: A computed tomography (CT) scan, which is sometimes done with contrast dye that is given by mouth or by enema, gives a more complete picture of the abdomen than a flat x-ray.
  • Stool Tests: If milk sugar or alcohol sugars are suspected of causing the gas, tests that show if there is too much fat in the stool might be ordered.
  • Breath Tests: Breath tests can determine if hydrogen is being produced in the small intestine, which could be a sign of small intestine bacterial overgrowth.

A physician might order other tests to determine the cause of gas or bloating.

Food And Symptom Diary

A physician may ask a person who is experiencing too much gas to record their diet and any symptoms, such as belching, bloating, and flatulence. By analyzing diet and timing of symptoms, it might become clear that a particular food or activity is leading to the excess gas. If such a diary does not help to pinpoint the source of the gas, other tests might be used to help diagnose the problem.

Swallowing Excess Air

One possible cause of frequent belching is swallowing excess air. There is no test to diagnose this problem, but the solution is in taking measures to prevent the swallowing of air. Not chewing gum or sucking on hard candy, and eating more slowly, can help reduce swallowed air. Sitting upright after eating can help prevent flatulence, and is especially helpful for people who have heartburn or gastroesophageal reflux disease (GERD).

Lactose Intolerance

Lactose intolerance is the inability to digest the sugar found in milk (lactose) and can either be congenital or acquired.
Rarely, an infant is born unable to digest milk sugar, which can lead to feeding problems early in life. More commonly, lactose intolerance develops after about the age of 2 years. When lactose passes into the digestive tract undigested, it can lead to symptoms of gas, bloating, and diarrhea.

Diagnosing lactose intolerance could be as simple as abstaining from eating or drinking milk products for a time and observing if the symptoms improve. If there is no change in the symptoms of gas, diarrhea, or bloating, then milk products are probably not the cause. There are also several tests that can be used to diagnose lactose intolerance, although they are not commonly used:

  • The lactose tolerance test, which is done by measuring blood glucose.
  • The hydrogen breath test, which tests a person's breath for hydrogen after they drink a solution containing lactose.
  • The stool acidity test, which is done by testing a person's stool for substances that may be a result of undiagnosed lactose.

If lactose intolerance is diagnosed, the treatment is avoiding all foods, medications, and beverages that contain lactose.

Sugar Alcohols

Sugar alcohols are sweeteners added to many foods in order to lower their calorie content, or to make them suitable to be consumed by people who have diabetes. Sorbitol, maltitol, mannitol, and xylitol are a few of the food additives that can cause gas and other digestive symptoms.

Sugar alcohols are not digested fully in the small intestine, and may pass into the large intestine, where they ferment and lead to symptoms of gas and diarrhea. Sorbitol is a sugar that is found naturally in certain fruits (apples, apricots, avocados, blackberries, cherries, nectarines, pears, and plums), and is created synthetically for use as a sugar substitute. Sorbitol and the other sugar alcohols can commonly be found in gum, candy, and other "sugar-free" foods.

Conditions That Cause Excess Intestinal Gas

In more rare cases, symptoms of gas, bloating, and pain might be caused by a disease or condition in the colon or in the abdomen.

Celiac disease: Celiac disease is the inability of the body to digest gluten, which is the protein found in wheat. When a person who has celiac disease ingests gluten, a host of symptoms can occur, including excess gas and abdominal bloating. Testing for the presence of celiac disease is a process that includes blood testing, endoscopy with an intestinal biopsy, and sometimes genetic testing. The treatment for celiac disease is avoiding eating gluten.

Diabetes: One complication of diabetes is the slowing down of the process of digestion. Slow digestion could cause food to pass through the small intestine not fully digested and consequently fermenting in the large intestine. Improper digestion could also cause small bowel bacterial overgrowth (see below).

Scleroderma: Some forms of scleroderma can adversely affect the gastrointestinal tract. A number of intestinal dysfunctions can lead to symptoms of abdominal distention or bloating, and gas. Scleroderma can also be associated with small bowel bacterial overgrowth (see below).

Small Bowel Bacterial Overgrowth: Small bowel bacterial overgrowth is caused when bacteria from the large intestine back up into the small intestine and grow out of control. Too much bacteria in the intestines can result in gas and bloating. Digestive conditions that put someone at risk for small bowel bacterial overgrowth include short bowel syndrome, irritable bowel syndrome (IBS), scleroderma, diabetes, and celiac disease.


Goldfinger SE. Patient information: Gas and bloating (Beyond the Basics)." UpToDate 19 Jul 2007. 9 April 2012.

National Digestive Diseases Information Clearinghouse (NDDIC). Gas in the Digestive Tract." National Institutes of Health (NIH). Jan 2008. 9 April 2012.

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