Abdominal Distention
Update October 17, 2018
Abdominal distension is the outward expansion beyond the normal girth of the abdomen or waist.
Patients may note increasing abdominal girth on the basis of increased clothing or belt size.
The causes of abdominal swelling can be remembered conveniently as the six Fs: flatus, fat, fluid, fetus, feces, or a “fatal growth” (often a neoplasm).
Flatus
Abdominal swelling may be the result of increased intestinal gas.
The normal small intestine contains gas made up of nitrogen, oxygen, carbon dioxide, hydrogen, and methane. Nitrogen and oxygen are consumed (swallowed), whereas carbon dioxide, hydrogen, and methane are produced intraluminally by bacterial fermentation.
Increased intestinal gas can occur in a number of conditions. Aerophagia, the swallowing of air, can result in increased amounts of oxygen and nitrogen in the small intestine and lead to abdominal swelling. Aerophagia typically results from gulping food; chewing gum; smoking; or as a response to anxiety, which can lead to repetitive belching. In some cases, increased intestinal gas is the consequence of bacterial metabolism of excess fermentable substances such as lactose and other oligosaccharides, which can lead to production of hydrogen, carbon dioxide, or methane.
Fat
Weight gain with an increase in abdominal fat can result in an increase in abdominal girth and can be perceived as abdominal swelling. Abdominal fat may be caused by an imbalance between caloric intake and energy expenditure associated with a poor diet and sedentary lifestyle; it also can be a manifestation of certain diseases, such as Cushing’s syndrome. Excess abdominal fat has been associated with an increased risk of insulin resistance and cardiovascular disease.
Fluid
The accumulation of fluid within the abdominal cavity (ascites) often results in abdominal distention and is discussed in detail below.
Fetus
Pregnancy results in increased abdominal girth. Typically, an increase in abdominal size is first noted at 12–14 weeks of gestation, when the uterus moves from the pelvis into the abdomen. Abdominal distention may be seen before this point as a result of fluid retention and relaxation of the abdominal muscles.
In the setting of severe constipation or intestinal obstruction, increased stool in the colon leads to increased abdominal girth. These conditions are often accompanied by abdominal discomfort or pain, nausea, and vomiting and can be diagnosed by imaging studies.
Neoplasms, abscesses, or cysts can grow to sizes that lead to increased abdominal girth. Enlargement of the intraabdominal organs, specifically the liver (hepatomegaly) or spleen (splenomegaly), or an abdominal aortic aneurysm can result in abdominal distention. Bladder distention also may result in abdominal swelling.