Distended Stomach and Causes of Enlarged Abdomen

In common terms, people tend to refer to the entire abdominal area as the stomach. However, the stomach is only one of the many organs that are contained within the abdominal cavity. Due to the interchangeable way in which the terms “stomach” and “abdomen” are used in ordinary conversations, the term “distended stomach” may refer either to a distension of the stomach or a distension of the abdomen.

For accurate descriptions, the entire abdominal area is usually subdivided into four quadrants. Based on their location, these four quadrants are referred to as the upper left quadrant, upper right quadrant, lower left quadrant, and lower right quadrant. The stomach is a stretchable, hollow organ that lies within the upper left quadrant of the abdomen. When empty, the stomach occupies less space within the abdominal cavity.

How does the stomach stretch?

Consumption of food or drink expands or distends the stomach to varying degrees. This distension of the stomach is usually not visible from the outside because the abdominal cavity has ample space to accommodate the normal expansion of the stomach. In some pathological cases, the distension of the stomach may be large enough to cause a visible swelling on the outer surface of the abdomen.

The abdominal cavity is enclosed by the abdominal wall. From inside to outside, the abdominal wall consists of an inner membranous covering known as the peritoneum, abdominal muscles, subcutaneous fat, and skin. No skeletal support is present within the abdominal wall. Organs are in close contact and press against each other.

Therefore, the abdomen is free to expand whenever there is an accumulation of gas, fluid, fat, or tissue mass within the abdominal cavity. When people refer to a distended stomach, they usually mean a distended abdomen. Abdominal distension may either span the entire abdomen or be localized to a certain region of the abdomen.

Distension vs. bloating

People may refer to abdominal distension in several ways. Distended stomach, swollen stomach, swollen abdomen, and abdominal bloating are some of the terms used to describe abdominal distension. Both swelling and distension refer to a visible increase in the girth of the abdomen.

However, the term bloating does not always mean a visible swelling. Bloating may also be used to refer to the sensation of fullness in the abdomen, rather than a visible increase in the girth of the abdomen. Overeating and indigestion are often associated with abdominal bloating.

Read more on abdominal fluid retention.

Causes of distended stomach (abdomen)

Distension of stomach or abdomen may affect either the entire abdomen or only a localized region of the abdomen. The following are the main causes of a generalized distension of the entire abdominal area:

  • Ascites: Ascites refers to accumulation of fluid within the abdominal cavity.
  • Peritonitis: Peritonitis refers to an inflammation of the peritoneal lining inside the abdominal cavity.
  • Intra-abdominal abscess: Intra-abdominal abscess refers to accumulation of pus inside the abdominal cavity.
  • Internal bleeding: Intra-abdominal bleeding can occur due to rupture of blood vessels within the abdominal cavity. Abdominal aortic aneurysm and trauma are possible causes of intra-abdominal bleeding.
  • Functional bloating: Functional bloating refers to a condition in which abdominal distension occurs for no known reason. Functional gastrointestinal disorders such as irritable bowel syndrome (commonly abbreviated as IBS) may be characterized by functional abdominal bloating.

Read more on excessive intestinal gas.

Localized distension

Localized distension can occur in any of the four abdominal quadrants. Some factors may be capable of causing abdominal distension in any abdominal area. For example, trauma to the abdominal wall or hernia involving abdominal organs can results in localized distension in any region of the abdomen. In other cases, the cause of abdominal distension may be specific to the abdominal area where the distension occurs.

Causes in the upper right quadrant

The following are some of the potential causes of distension that may occur in the right upper quadrant of the abdomen:

  • Hepatomegaly: Hepatomegaly refers to an enlargement of the liver, which lies within the upper right quadrant of the abdomen. In case of massive hepatomegaly, the liver may even expand into the upper left quadrant of the abdomen. The main causes of hepatomegaly include cirrhosis, alcoholic liver disease, viral hepatitis, autoimmune hepatitis and liver cancer (primary hepatocellular carcinoma).
  • Heart failure: Heart failure refers to a condition in which the heart is unable to carry out its normal function of pumping blood. A variety of factors can cause heart failure, including high blood pressure, defects in heart valves, coronary artery disease, congenital heart defects, inflammation of cardiac muscles, cardiomyopathy, and irregular heartbeats (arrhythmias).
  • Gallbladder: The main gallbladder diseases include formation of gallstones, inflammation of the gallbladder (cholangitis), and gallbladder cancer.
  • Right kidney: Hydronephrosis, polycystic kidney disease, and renal carcinoma of the right kidney can cause distension of the upper right quadrant of the abdomen.
  • Colon: Diseases that affect the upper part of the colon in the right abdominal quadrant (such as the upper region of the ascending colon, hepatic flexure and first half of the transverse colon) can cause abdominal distension in the upper right quadrant. Examples of colon diseases include colitis, diverticulosis, blocked colon and colon cancer.

Causes in the upper left quadrant

  • Massive hepatomegaly: Massive hepatomegaly may cause distension of both upper left and upper right quadrants of the abdomen.
  • Splenomegaly: Enlargement of spleen can occur in lymphoma, leukemia, hemolytic anemia, blood-borne infections, myelofibrosis, cirrhosis, thrombosis in splenic or portal vein, polycythemia rubra vera, and heart failure.
  • Hepatosplenomegaly: Both liver and spleen can become enlarged in conditions such as lymphoma, cirrhosis, amyloidosis, and myeloproliferative diseases.
  • Left kidney: Diseases affecting the left kidney can occur due to the same reasons that cause right kidney disease.
  • Stomach: Stomach polyps, stomach cancer, and delayed gastric emptying in conditions such as gastroparesis or pyloric stenosis can cause distension of the upper left abdominal quadrant.
  • Pancreas: Pancreatic diseases include pancreatic pseudocyst, pancreatitis, pancreatic abscess, and pancreatic cancer.
  • Colon: Diseases that affect the left part of the transverse colon, splenic flexure, and first part of the descending colon can cause abdominal distension in the upper left quadrant.
  • Aorta: Aortic aneurysm of the abdominal aorta is more likely to cause distension in the middle part of the abdomen. Rupture of aorta and accumulation of blood in the abdominal cavity can also cause generalized abdominal distension.

Causes in the umbilical region

Massive splenomegaly, massive hepatomegaly, paraumbilical hernia, Crohn’s disease, and intestinal obstruction are some of the causes of abdominal distention in the umbilical region.

Causes in the suprapubic region

Diseases of the prostate gland, urinary bladder and uterus can result in abdominal distension in the suprapubic region between the navel and the external genitalia.

Causes in the lower abdominal quadrants

Abdominal distention in the lower left and lower right quadrants can be caused by appendicitis, tumors (both benign and malignant), abscess, intestinal obstruction, gas accumulation, fecal impaction, constipation, ovarian cysts, ovarian tumors, and ectopic pregnancies.

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