Abdominal swelling is a manifestation of numerous diseases. Patients may complain of bloating or abdominal fullness and may note increasing abdominal girth on the basis of increased clothing or belt size. Abdominal discomfort is often reported, but pain is less frequent. When abdominal pain does accompany swelling, it is frequently the result of an intraabdominal infection, peritonitis, or pancreatitis. Patients with abdominal distention from ascites (fluid in the abdomen) may report the new onset of an inguinal or umbilical hernia. Dyspnea may result from pressure against the diaphragm and the inability to expand the lungs fully.
The causes of abdominal swelling can be remembered conveniently by the six Fs: flatus, fat, fluid, fetus, feces, or a “fatal growth” (often a neoplasm).
Abdominal swelling may be the result of increased intestinal gas. The normal small intestine contains approximately 200 mL of 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 leads to repetitive belching. In some cases, increased intestinal gas is the result of bacterial metabolism of excess fermentable substances such as lactose and other oligosaccharides that can lead to production of hydrogen, carbon dioxide, or methane. In many cases, the precise cause of abdominal distention cannot be determined. In some persons, particularly those with irritable bowel syndrome and bloating, the subjective sense of abdominal pressure is attributable to impaired intestinal transit of gas rather than increased gas volume. Abdominal distention, an objective increase in girth, is the result of a lack of coordination between diaphragmatic contraction and anterior abdominal wall relaxation in response to an increase in intraabdominal volume loads. Occasionally, increased lumbar lordosis accounts for apparent abdominal distention.
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 the result of an imbalance between calorie intake and energy expenditure associated with a poor diet and sedentary lifestyle and 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 within the abdominal cavity, or ascites, often results in abdominal distention and is discussed in detail below.
Pregnancy results in increased abdominal girth. Typically, an increase in abdominal size is first noted at 12 to 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.
Increased stool in the colon, in the setting of severe constipation or intestinal obstruction, also leads to increased abdominal girth. These conditions often are accompanied by abdominal pain, nausea, and vomiting and can be diagnosed by imaging studies.
An abdominal mass can result in abdominal swelling. 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. In addition, malignancies, abscesses, or cysts can grow to sizes that lead to increased abdominal girth.
History and Physical Examination
Determining the etiology of abdominal swelling begins with history-taking and a physical examination. Patients should be questioned regarding symptoms suggestive of malignancy, including weight loss, night sweats, and anorexia. Inability to pass stool or flatus together with nausea or vomiting suggest bowel obstruction, severe constipation, or an ileus (lack of peristalsis). Increased eructation and flatus may point toward aerophagia or increased intestinal production of gas. Patients should be questioned about risk factors for or symptoms of chronic liver disease, including excessive alcohol use and jaundice, which suggest ascites. Patients should also be asked about other symptoms of medical conditions, including heart failure and tuberculosis, which may cause ascites.
Physical examination should assess for signs of systemic disease. The presence of lymphadenopathy, especially supraclavicular lymphadenopathy (Virchow's node), suggests metastatic abdominal malignancy. Care also should be taken during the cardiac examination to evaluate for elevation of jugular venous pressure (JVP); Kussmaul's sign (elevation of the JVP during inspiration); or a pericardial knock, which may be seen in heart failure or constrictive pericarditis, as well as a murmur of tricuspid regurgitation. Spider angiomas, palmar erythema, dilated superficial veins around the umbilicus (caput medusae), and gynecomastia suggest chronic liver disease.
The abdominal examination should begin with inspection for the presence of uneven distention or an obvious mass. Auscultation should follow. The absence of bowel sounds or the presence of high-pitched localized bowel sounds point toward an ileus or intestinal obstruction. An umbilical venous hum may suggest the presence of portal hypertension, and a harsh bruit over the liver is heard rarely in patients with hepatocellular carcinoma or alcoholic hepatitis. Abdominal swelling caused by intestinal gas can be differentiated from swelling caused by fluid or a solid mass by percussion; an abdomen filled with gas is tympanic, whereas an abdomen containing a mass or fluid is dull to percussion. The absence of abdominal dullness, however, does not exclude ascites, because a minimum of 1500 mL of ascites is required for detection on physical examination. Finally, the abdomen should be palpated to assess for tenderness, a mass, enlargement of the spleen or liver, or presence of a ...