Abdominal enlargement may be due the presence of abdominal fat, feces within the bowel, fluid accumulation, fetus in the pregnant uterus or flatus (intestinal gas). These are the most common causes although there are a number of other causes that may cause generalized distension of the abdomen or bulging within a specific abdominal quadrant as discussed under Abdominal Distension.
Various terms, both common and medical, are used to describe different types of abdominal distension. Abdominal bloating often refers to distension due to gas accumulation mainly within the bowels. Abdominal swelling refers to fluid accumulation within the abdominal cavity or organs lying within the abdominal cavity (both intraperitoneal and retroperitoneal). The medical term for abdominal swelling due to fluid accumulation is known as ascites.
The visceral peritoneum is a thin sheet that covers the organs like the liver, spleen, stomach, gallbladder, small intestine, transverse and sigmoid colon, uterus, fallopian tubes and ovaries. These organs, known as the intraperitoneal organs, can move freely in the area contained by the visceral peritoneum and do not rub against the abdominal wall. There is little or no intraperitoneal fluid, although some women may have as much as 20 ml of fluid in this area, which can vary with the menstrual cycle.
Another peritoneal layer known as the parietal peritoneum lines the abdominal wall. Between the visceral and parietal peritoneum is the potential space known as the peritoneal cavity which contains a thin layer of fluid to prevent friction during movement. The peritoneal membranes attach these organs to the abdominal wall. Some organs are partly covered by the peritoneum or lie between the peritoneum and abdominal wall and are known as extraperitoneal or retroperitoneal organs. Refer to the article on the Peritoneal Cavity for more information on the peritoneum, mesentery and omentum.
Signs and Symptoms Associated With Abdominal Swelling
While a minute amount of fluid in the peritoneal cavity is necessary for lubrication, a large collection of the fluid will cause visible abdominal swelling. Small amounts of fluid, less than 500 milliliters, may only cause moderate abdominal distension if any but can be detected on an ultrasound. In severe cases, up to 20 liters of serous fluid can accumulate in the peritoneal cavity. Apart from the massive abdominal swelling, the umbilicus (belly button) will appear flat or everted (protrude outwards).
While pain may be a localised feature of the diseases organ, in peritonitis, widespread abdominal pain is reported. Fever may be present is the swelling is due to infectious causes or less commonly with cancer and autoimmune conditions. Family Mediterranean fever may present with a fever and abdominal swelling that is of unknown origin and chronic. Other signs and symptoms of peritonitis may include :
- Changes in bowel movement (usually diarrhea)
- Change in appetite, usually loss of appetite
- Nausea and/or vomiting
Causes of Abdominal Swelling
Many pathological process that may or may not involve the peritoneal layers can result in fluid accumulation within the peritoneal cavity. This can be a result of excess serous fluid, known as ascitic fluid, in ascites. When blood accumulates within the peritoneal cavity in cases of mechanical trauma then this is known as a hemoperitoneum or hematoperitoneum.
The process behind ascites is explained under the Pathophysiology of Edema.
Some of the more common causes of abdominal swelling involves a number of liver and/or cardiac conditions that may result in ascites as a result of portal hypertension. The more common causes in these cases include :
- Hepatic cirrhosis
- Congestive heart failure
Other causes may include :
- Alcoholic hepatitis or liver disease
- Liver failure
- Constrictive pericarditis
- Liver cancer
- Tricuspid regurgitation (heart valve insufficiency)
- Hepatic vein obstruction (Budd-Chiari syndrome)
Low levels of albumin in the blood, known as hypoalbuminemia, may also cause ascites. This may be seen in:
- Nephrotic syndrome
- Protein-losing enteropathy
- Severe malnutrition
Another cause of ascites is water and salt retention. Some of the causes include :
- Kidney failure
- IV fluid administration
- Excess ADH – syndrome of inappropriate ADH secretion (SIADH)
Ascites may arise as when certain abdominal organs, particularly intraperitoneal organs, are diseased although the peritoneum may be unaffected. This includes pathology of the :
- Pancreas (pancreatic ascites)
- Gallbladder or bile ducts (bile ascites)
- Lymphatic vessel (chylous ascites)
- Bladder and/or ureter (urinary ascites)
- Ovaries (ovarian ascites)
Advanced cancer of abdominal organs may also result in ascites (malignant ascites), can spread to the peritoneum (peritoneal carcinomatosis) or originate in the peritoneum (primary mesothelioma).
Peritonitis is the inflammation of the peritoneum as a result of :
- Infections – bacterial, fungal, tuberculous, human immunodeficiency virus (HIV)
- Cancer – peritoneal carcinomatosis, primary mesothelioma
- Chemical irritation – bile, blood or barium
- Renal dialysis
- Endocrine disorders
- Autoimmune conditions like SLE (systemic lupus erythematosus), vasculitis
Other causes of abdominal swelling are listed under Abdominal Distension.
- Ascites. Emedicine
Article reviewed by Dr. Greg. Last updated on November 19, 2010