Eduardo E. Baravalle

Abdominal circumference may increase, permanent or temporary, progressive, stationary or transitory, evidenced by the need to give more width to the belt or by an increase in the size of clothing, is a frequent and common reason for consultation. It can be the initial manifestation of a systemic disease.

Intestinal gas. Abdominal bloating can be caused by increased intestinal gas, by the accumulation of fluid in the abdominal cavity, or by the presence of tumors. The existence of  pregnancy, rarely, should be considered.

The volume of gas present in the intestinal tract at any given time can be measured by plethysomography and by a technique that uses rapid infusion of argon to flush out the gas in the intestine. Normal subjects contain less than 200 ml of gas, both fasting and after meals. Intestinal gas comes from three different sources: swallowed air, intraluminal gas production, and diffusion from the bloodstream.

The gas present in the stomach comes from the swallowed air, and in this sector the intraluminal production is minimal. With each inspiration a small amount of air reaches the stomach, and so do a few milliliters when each bolus of saliva or food is swallowed. Most of the gastric air is removed by regurgitation. The fraction of air going into the duodenum is influenced by position.

Three gases, carbon dioxide, hydrogen, and methane are produced in the intestinal lumen in appreciable quantities. Hydrogen and methane derive from bacterial metabolism. Hydrogen-producing bacteria are in the colon and require fermentable substrates from the diet (carbohydrates and proteins). A fraction of the hydrogen released in the colon is absorbed and then excreted by the lungs. In this sense, there is a good correlation between the hydrogen from respiration and the excretion of hydrogen produced in the colon, measured by gas infusion techniques. An increase in breath hydrogen after carbohydrate intake is a good test for carbohydrate malabsorption.

Methane originates from the metabolism of colonic bacteria, and may have more to do with environmental than genetic factors. Recently, a higher than expected prevalence of methane production has been suggested in patients with colon cancer.

Colon gas has good lipid and blood solubility, and diffuses passively, determined by the partial pressure of each gas, with a bidirectional flow.

Ascites.  Is the  accumulation in the peritoneal cavity, is caused by: 1) an increase in the permeability of the peritoneal capillaries induced by inflammatory or neoplastic diseases of the serosa; 2) decrease in plasma osmotic pressure of any origin, and 3) increase in capillary pressure in the liver sinusoids, caused by liver cirrhosis, obstruction of the suprahepatic veins or of the inferior cava, heart failure, constrictive pericarditis. In addition, the state of renal function is important in the genesis of ascites.


The main causes of abdominal bloating are classified in the following table.

Abdominal bloating due to increased intra-abdominal gas (without ascites)

  • Aerophagia
  • Irritable colon
  • Malabsorción
  • Intestinal subocclusion
  • Intestinal occlusion
  • Posquirurgical 

Abdominal bloating with ascites (transudate)

  • Hepatic cirrhosis
  • Congestive heart failure
  • Nephrotic syndrome
  • Budd-Chiari syndrome
  • Obstruction of the portal veins or inferior cava
  • Proteinoretic gastroenteropathy

Abdominal bloating due to increased size of the viscera 


Abdominal bloating can be subjective and is generally described as a feeling of fullness; it usually corresponds to functional disorders of the gastrointestinal tract when not accompanied by clinical findings on physical examination.

Accompanying symptoms

Abdominal bloating can be noticed after weeks or months, due to a gradual and insidious development, or due to the presence of coexisting factors (obesity, pregnancy). The presence of pain is related to the involvement of an abdominal organ. The pain will be localized in the liver of stasis, colonic neoplasms and splenomegalies and diffuse in peritonitis, pancreatitis, and intestinal occlusion. Pain is rare in cirrhotic patients, so when  is present, hepatoma or peritonitis should be considered. Patients with lower limb edema and bloating may have Ascites. If the swelling appeared before in the limbs, heart failure should be considered, and if it did later, cirrhosis and constrictive pericarditis are posible.

Presentation forms

If the abdominal distension is intermittent, the most common cause is the irritable colon. If it is permanent, it is usually due to the development of ascites or the presence of an intra-abdominal mass. If it has presented insidiously, ascites should be considered; if development has been rapid, ascites, intestinal obstruction, or abdominal mass should also be considered. Pleural effusion can aggravate dyspnea, tachypnea, and orthopnea caused by abdominal tumors or tension ascites.

Patients with ascites should be questioned about their alcohol intake, previous episodes of hematuria, or jaundice, or a history of past rheumatic disease.

Findings on physical examination

A careful and complete physical examination can provide important data for the diagnosis of bloating.

Inspection:  Collateral circulation, palmar erythema, gynecomastia, arachnid nevi, and parotid hypertrophy are clinical signs that accompany liver disease.

A tense abdomen, with thinned skin and an everted navel, is characteristic of the existence of ascites. An asymmetric enlargement of the abdomen suggests intestinal obstruction or abdominal tumor. A metastatic liver may be visible upon inspection as a nodular mass in the right hypochondrium, which is mobilized by respiration. Likewise, an epigastric mass showing peristaltic movements from left to right should lead to suspicion of pyloric obstruction.

Auscultation: In intestinal obstruction, high-pitched noises or sucking sounds may be heard due to increased fluid and gas in the large intestine. A venous murmur in the navel, due to increased perihepatic flow, should suggest portal hypertension; a murmur in the liver area will force one to think of hepatocarcinoma.

Percussion: The existence of tympanism or its increase is characteristic of gas distension; tympany in flanks and hypogastrium, with central dullness, of the ovarian cyst.

The presence of liquid wave and the sign of unevenness, together with dullness in flanks and hypogastrium, is suggestive of ascites. In obese subjects, small amounts of fluid can be difficult to demonstrate. When in doubt, paracentesis is the maneuver of choice.

Loss of liver dullness may be due to the interposition of intestinal gas, the presence of free gas in the abdominal cavity, or massive liver necrosis.

Palpation: Palpation of the abdomen with tension ascites presents difficulties. Splenomegaly associated with ascites may be a physical examination finding that suggests cirrhosis. When there is portal hypertension, the presence of a soft liver should suggest portal obstruction; if the liver is firm, in cirrhosis; and if it is hard and not * dular, in a primary or metastatic tumor with ascites. Palpation of a pulsatile liver associated with ascites leads one to think of tricuspid regurgitation. The presence of a hard periumbilical ganglion suggests metastasis of a gastrointestinal or pelvic tumor, while a hard left supraclavicular lymphadenopathy raises the suspicion of a metastasis of a gastrointestinal or pancreatic tumor.

Rectal and pelvic examination can demonstrate the presence of masses produced by neoplasms or infections at that level

Study methodology

Complementary examinations are essential to confirm or extend the information obtained in the interrogation or in the physical examination.

Paracentesis or ultrasonography can be useful to demonstrate the presence of ascites. The paracentesis, or abdominal puncture for the extraction of ascitic fluid, is used to determine whether it was from an exudate (protein content greater than 2.5 g / 100 ml) or a transudate (protein content less than 2.5 g / 100 me). The number of leukocytes and their type are determined in the ascitic fluid: less than 250 (transudate: cirrhosis, nephrotic syndrome); less than 1000 with predominance of mesothelial cells (heart failure); greater than 1000, of variable type, in neoplasms; greater than 1000 with predominance of lymphocytes, in tuberculous peritonitis; greater than 1000 with polymorphonuclear predominance, in bacterial peritonitis. Glucose decreases in bacterial and neoplastic ascites.

Cytological study can demonstrate neoplastic cells in intra-abdominal tumor processes. Gram stains, Ziehl-Nielsen stains, and cultures are important in peritoneal infections.

Functional liver tests are used to detect liver cirrhosis. The CBC may reveal anemia in malignant processes, and if it is macrocytic, it may suggest liver disease or malabsorption. Amylase will be increased, in pancreatitis.

Ultrasonography and computerized axial tomography are useful to determine the presence of masses or to assess the size of the liver and / or spleen.

Plain abdominal radiography can show bloating of the colon and also give information about the size of the liver and spleen. An elevated and irregular right diaphragm may suggest a liver tumor or abscess at that level. Occasionally, balitable studies of the gastrointestinal tract are needed to locate the primary tumor, esophageal and / or gastric varices, malabsorption pattern, intestinal occlusion, which orient towards the disorder that produces abdominal distension.

Laparoscopy and liver biopsy are used for the histological demonstration of liver cirrhosis, hepatomas, and intra-abdominal neoplasms.