Ascites can be a symptom of many types of cancer. The types of cancer that are more likely to cause ascites are cancer of the breast, lung, large bowel (colon), stomach, pancreas, ovary and the lining of the womb (endometrium).

There may be several reasons for the build-up of ascites:

If cancer cells have spread to the lining of the abdomen, they can irritate it and cause fluid to build up.
If the liver is affected by cancer cells, this may block the circulation of blood through the liver, which can lead to a build-up of fluid in the abdomen.
If the liver is damaged, it may produce less blood protein. This may upset the body's fluid balance, which causes fluid to build up in the body tissues, including the abdomen.
Cancer cells can block the lymphatic system. The lymphatic system is a network of fine channels which runs throughout the body. One of its functions is to drain off excess fluid, which is eventually got rid of in the urine. If some of these lymphatic channels are blocked, the system cannot drain efficiently and fluid can build up.