Ascites is an accumulation (effusion in medical terms) of liquid in the peritoneum, a normally empty space which covers the abdominal organs. Ascites is painless and is only diagnosed once a large volume of liquid is accumulated. The main causes of ascites are liver diseases notably cirrhosis and cancer of the peritoneum or the digestive tract. A sample of the liquid is often taken for analysis which gives information about its origin. The presence of cancerous cells in ascites signals a tumor as the cause, notably liver, digestive, or ovarian cancers, that would then have to be identified.