Ascites occurs when fluid accumulates in the abdomen. This buildup occurs between two membrane layers that together make up the peritoneum, a smooth sac that contains the body's organs. It is usual to have a small amount of fluid in the peritoneum cavity.
This fluid buildup causes swelling that usually develops over a few weeks, although it can also happen in just a few days. Ascites is very uncomfortable and causes nausea, tiredness, breathlessness, and a feeling of being full. Liver disease is the most common cause of ascites. Other causes typically include cancer and heart failure.