There is no difference between ascites and peritoneal effusion; ascites is a colloquial term and peritoneal effusion is a written term. Clinically, there are leaking fluid and exudate in common peritoneal fluid. The so-called leaking fluid mainly refers to the fluid caused by the increase of intra-abdominal pressure due to portal hypertension, cirrhosis, etc. The so-called exudate is often caused by inflammatory infection due to mesenteric lymphadenitis and peritonitis. Of course, for some cases of tumors in the abdomen, such as gastric cancer, colorectal cancer or gynecological tumors, they can also manifest as peritoneal fluid, and most of these cases are bloody ascites, and in this kind of bloody ascites, when the examination of ascites is completed and the tumor cells are looked for, obvious cancer cells can be found.