The abdomen contains many of our vital organs (liver, spleen, stomach), is lined with membranes and contains a fluid called peritoneal or ascitic fluid. This fluid provides lubrication to the organs and reduces friction between tissues. In a healthy adult, the volume is fairly small (around 75 mls) and there is constant production and absorption of the fluid. If an imbalance between production and absorption occurs, accumulation of fluid results. This condition is known as ‘ascites’.
In severe cases, excess fluid can reach volumes of up to 10 liters and will be clearly visible from abdominal swelling. The large volume of fluid can result in increased pressure within the abdomen, resulting in impaired organ function. In milder cases, volumes of accumulated fluid may be relatively small and will only be visible under ultrasound examination. There are numerous diseases that can result in ascites and diagnosis can be difficult, requiring a detailed examination and knowledge of a patient’s medical history.
Ascites can be classified medically as being a transudate or exudate. Transudates are usually due to an increased pressure in blood vessels, the most common causes being liver and heart disease. An exudate is usually due to inflammation or malignancy. Transudates and exudates show different composition; for example transudates are low in protein whilst exudates are high in protein. Therefore laboratory analysis of the fluid can help point to the underlying causes of ascites.
Causes of Ascites
Cirrhosis of the liver: ascites occurs in around half of patients suffering from cirrhosis of the liver. The most common cause of this condition being sustained alcohol misuse. Damaged liver cells are replaced with fibrotic material, the process sometimes being described as ‘scarring of the liver’. One of the effects of this is an increase in the amount of fluid and protein passing from blood vessels into the liver. When this fluid exceeds a level that the abdominal lymphatics can deal with, fluid accumulates.
Heart disease: one of the effects of severe cardiac failure on the right side of the heart is a build up of fluid in the liver. This fluid can pass into the abdominal cavity and hence cause ascites.
Cancer: Several malignancies that arise in the abdominal cavity can result in ascites. These include ovarian cancer, malignant mesothelioma, peritoneal angiosarcoma and lymphoproliferative disorders. More commonly however, tumors originating outside the abdominal cavity cause ascites. For example, tumors from the breast, endometrium and colon often spread to the peritoneum and cause an accumulation of ascitic fluid.
Tuberculosis: the pathogenic organism that causes tuberculosis, mycobacterium, can spread from the lungs to the peritoneum and cause ascites.
Less common causes: in rare cases, ascites is seen in patients with pancreatic disease, endometriosis and fungal infections.
Treatment of Ascites
Treatment of the underlying cause: for example, surgery to remove a tumor followed by chemotherapy will be required to treat malignant ascites. Anti-microbial therapy is used to treat infectious ascites caused by T.B. In severe cases of cirrhosis, liver transplant is the only treatment option.
Drainage: excess ascitic fluid can be drained via insertion of a needle into the peritoneal cavity. This procedure, known as parecentesis, is relatively straight forward. The fluid can be examined for protein content, blood cells and infectious organisms in order to aid diagnosis.
Diuretics: these drugs encourage the production of urine, and hence loss of fluid from the body, and can be effective at alleviating symptoms in some patients.
Low sodium diets: in some cases sodium retention by the kidneys can exacerbate ascites, and therefore reduction of dietary salt can be helpful.
Management of Ascites, F.A. Rochling & R.K. Zetterman, Drugs 2009,69(13) P1739-1760