Fluid dark areas refer to pleural effusion, abdominal effusion, pelvic effusion, and pericardial effusion. There are many causes of fluid dark areas, such as pericardial effusion caused by heart failure; pericardial effusion caused by tuberculous pericarditis; carcinomatous pericardial effusion caused by cancerous invasion of the pericardium; pleural effusion caused by tuberculous pleurisy caused by tuberculous invasion of the pleura; carcinomatous hydrothorax caused by metastatic tumors that invade the pleura; and hemorrhagic pleural cavity caused by thoracic trauma. Effusion. Peritoneal effusion caused by cirrhosis of the liver; peritoneal effusion caused by fulminant hepatitis and primary hepatocellular carcinoma. Carcinomatous peritoneal effusion caused by abdominal malignant tumor invading the peritoneum, e.g., ascites caused by ovarian cancer invading the peritoneum; bloody effusion caused by ectopic pregnancy. Organ rupture, such as bloody effusion caused by splenic rupture, hepatic rupture and so on.