Accordingly, it is known by different names: water vapor and clouds in the sky; seawater and icebergs in the ocean; glaciers and rivers in the mountains; and aquifers in the ground. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units. X-rays of the small intestine, in which barium is used to fill and outline the small intestine, are particularly useful for determining whether there is an obstruction of the small intestine. Fructose, on the other hand, may be digested normally but may pass so rapidly through the small intestine that there is not enough time for digestion and absorption to take place. Of course, some types of fiber may lead to increased production of gas because they are digested to some extent by colonic bacteria. Thus, as already described, lactose and sorbitol may be poorly digested by the pancreatic enzymes and small intestine.

An obstruction in the small bowel, which is most commonly due to adhesions (scarring that kinks the intestines) from previous surgery, is another cause of intermittent abdominal distention. Imaging studies, including ultrasound examination, computerized tomography (CT), and magnetic resonance imaging (MRI), are particularly useful in defining the cause of distention that is due to enlargement of the abdominal organs, abdominal fluid, and tumor. Specific tests can be done for maldigestion of individual sugars that are commonly maldigested, including lactose (the sugar in milk) and sorbitol (a sweetener in low-calorie foods). Often, a dietitian can be of great help in dealing with specialized diets and identifying foods that can be most at fault. For example, the problem may be the foul odor of the gas (often due to ingestion of sulfur-containing foods), the lack of ability to control (hold back) the passing of gas, or the soiling of underwear with small amounts of stool when passing gas. Dietary fat reaching the small intestine causes the transport of digesting food, gas, and liquid within the intestines to slow.

Some people appear to be very sensitive (hypersensitive) to the distention of their intestines, and they may feel bloated even with normal amounts of digesting food, gas, and fluid in the intestine after a meal. It is normal to pass gas up to 20 times a day. When individuals complain of flatulence, it may be useful for them to count the number of times they pass gas for several days. When the obstruction is incomplete, the food, air, and fluid eventually pass into the intestines and the bloating/distention resolves. This can promote the accumulation of food, gas, and liquid, and lead to bloating and/or distention. A delay in emptying of the radioactivity from the stomach can be caused by any condition that reduces emptying of the stomach (for example, pyloric stenosis, gastroparesis). To make matters worse, the distention that is caused by the physical obstruction stimulates both the stomach and intestines to secrete fluid, which adds to the distension. A functional obstruction is not caused by an actual physical blockage, but rather by the poor functioning of the muscles of the stomach or intestines that propel the intestinal contents. Fats in food affect the intestine which mimics a functional obstruction.

Then, during the next hour or two, the stomach secretes acid and fluid, which mix with the food and assist indigestion. As a result, the stomach distends further. For example, if the air is in the stomach, emptying the stomach is likely to be the problem. If an individual complains of excessive gas but passes gas less than 20 times per day, the problem is likely to be something other than too much gas. If the bloating or distention is associated with increased flatulence, then bacteria and excessive gas production are likely factors. Dietary fiber or fiber used for treating constipation can cause bloating without increasing the production of gas in the intestine. Simple X-rays of the abdomen, particularly if they are taken during an episode of bloating or distention, often can confirm air as the cause of the distention, since large amounts of air can be seen easily within the stomach and intestine.