What is Ascites

The organs of the abdomen are contained in a sac or called the peritoneum. Normally the peritoneal cavity contains no fluid, although in women a small amount of about 20ml exists. Ascites is the term used to denote a fluid collection in the peritoneal cavity, a situation that is not normal.

There are a variety of diseases that can cause the fluid to accumulate and the reasons ascites occurs may be different for each disease. Cancer that spreads to the peritoneum can cause direct leakage of fluid, while other illnesses cause excess accumulation of water and sodium in the body. This fluid can eventually leak into the peritoneal cavity.

Most commonly, ascites is due to liver diseases and the inability of that organ to produce enough protein to retain fluid in the bloodstream. Normally, water is held in the bloodstream by oncotic pressure. The pull of proteins keeps water molecules from leaking out of the capillary blood vessels into surrounding tissues. As liver disease advances, its ability to manufacture proteins is decreased, so oncotic pressure decreases because of the lack of  protein in the body, and water leaks into the surrounding tissues.

1.      Cirrhosis describes a form of liver failure in which liver tissue that is damaged is replaced by scar tissue. As more liver tissue is lost,  progressive liver failure occurs.

2.      Acute liver failure can result in ascites. This may be due to any acute injury to liver cells including adverse reactions to medications or drug abuse.

3.      Budd-Chiari syndrome is caused by the blockage of the hepatic veins (those that drain the liver).

Other causes of ascites include:

1.      Heart failure is the inability of the heart muscle to adequately pump the fluid within the blood vessels. This can cause a variety of problems, but most notably, fluid backs up into the lungs and other organs causing them to fail. This water overload can cause leakage into the peritoneal cavity and the formation of ascites.

2.      Nephrotic syndrome, in which kidney damage causes protein to leak into the urine, decreases oncotic pressure and may result in ascites.

3.      Direct irritation of the peritoneum can cause it to leak fluid as part of the inflammation process. This irritation may be due to a malignancy (cancer) or infection.

4.      Diseases of the ovary can be associated with ascites.

There is a distinction between patients who develop ascites because of liver disease and cirrhosis, and those who develop it because of inflammation of the peritoneum because of cancer. Liver disease tends to be relatively painless, while cancer patients experience significant amounts of pain.

Otherwise, the symptoms are similar. There is swelling of the abdomen to accommodate the fluid build up. This may make it difficult for the diaphragm (the flat muscle that separates the chest form the abdomen) to assist with breathing, causing shortness of the breath.

While a tense abdomen filled with fluid is easy to recognize, initially, the amount of ascites fluid may be small and difficult to detect. As the amount of fluid increases, the patient may complain of fullness or heaviness in the abdomen. It is often the signs of the underlying disease that initially brings the patient to seek medical care.

In cirrhosis of the liver, not only does fluid accumulate in the abdominal cavity, but there may be leg swelling, easy bruising, enlargement of the breasts, and confusion..

If the ascites is due to heart failure, there may be shortness of breath as well as leg swelling (edema). Patients with cancer may complain of pain, weight loss, and  fatigues in association with the abdominal distention.

In general, unexplained abdominal swelling for any cause is a reason to seek medical care. For those who have known ascites, fever and abdominal pain should be a warning that the fluid may be infected and care should be accessed immediately.