Abdominal distension (enlargement of the abdomen) is most commonly due to one of the following :

  • Fat
  • Fluid
  • Feces
  • Flatus
  • Fetus

Bloating that is transient and may come on suddenly and pass just as quickly is more likely due to gas accumulation within the gut. While fluid may also cause bloating, often the term ‘bloat’ is associated with gas while abdominal swelling is attributed to fluid accumulation (ascites).

Causes of Abdominal Gas Bloating

Abdominal bloating refers to a clearly visible distension of the abdomen. This is in contrast to the feeling of being bloated which is a sensation of fullness in the abdomen, usually in the upper parts of the abdomen.

Gas production within the alimentary tract is a normal occurrence. It arises as a result of gas being produced during chemical digestion, the byproduct of bacteria consuming nutrients within the gut and decomposition of waste. Two very common and non-pathological causes of gas bloating is the swallowing of air, which is known as aerophagia, and the consumption of carbonated beverages like fizzy soda, beer and sparkling wine.

The gut contains less than 200 milliliters of gas although anywhere between 1 to 2 liters of gas is passed out in a day. In most cases associated with abdominal gas bloating, excessive belching or flatulence, the volume of gastrointestinal gas is not larger than normal.

Although rare, gas outside the bowels but within the abdominal cavity is known as pneumoperitoneum. It is a result of perforation of the stomach or intestines, as gas escapes from the gut into the peritoneal cavity. This is usually very painful and considered as a medical emergency as microorganisms from the gut will enter the sterile peritoneal cavity and result in a serious, even life-threatening, infection (peritonitis).

Signs and Symptoms of Abdominal Gas Bloating

Abdominal bloating as a result of gas accumulation within the gut may result in a number of signs and symptoms apart from the visible enlargement of the abdomen. This includes :

Changes in bowel movement, like loose stool to diarrhea or constipation, and a general sense of feeling unwell or lethargic may also be present. These signs and symptoms may occur independently as concomitant features of the cause or may be a result of gas accumulation within the gut.

The enlargement is usually generalized throughout the abdomen as a result of gas accumulation. Rarely pockets of gas are trapped in one section of the bowel, usually the colon, where it will cause a visible and palpable bulge in one quadrant of the abdomen.

Conditions that Cause Abdominal Gas Bloating

A number of conditions may result in abdominal bloating due to gas accumulation within the gut. These causes are discussed further under :

Irritable bowel syndrome (IBS)

Abdominal bloating is one of the features of IBS, although the gas volume within the bowel does not appear to be greater than normal. Gas bloating may occur very suddenly and can severe to the extent that the abdominal distension can become painful due to stretching of the abdominal wall and even alter the usual clothing sizes.

Infections

Some of the following infectious conditions may result in abdominal bloating due to gas accumulation.

Food Intolerance and Malabsorption

The inability to digest or absorb the following substances may provide additional nutrition for the the naturally occurring intestinal bacteria to consume. Gas is often produced as a byproduct by these bacteria. In addition, the decomposition of these nutrients will also contribute to gas accumulation.

Maldigestion

The ability to digest certain or all foods may be compromised as a result of inactivation of digestive enzymes or a lack of these enzymes. The control mechanisms involving the digestive hormones or nerve supply to the gut may also be compromised.  This is discussed further under Digestive Problems.

Gastrointestinal Motility

The rapid or slow transit of food and chyme through the gastrointestinal tract may impair both digestion and absorption. This may be due to weak muscle activity or lack of coordination in peristalsis, obstructions or resection or strangulation of the bowels.


Article reviewed by Dr. Greg. Last updated on November 16, 2010