To determine whether the pleural and abdominal fluid is exudate or leakage fluid, it is necessary to extract an appropriate amount of fluid to improve the routine examination, cytological examination, and biochemical examination and comprehensive judgment. 1. Routine examination. Including color (leakage fluid is mostly yellowish; exudate fluid is dark yellow, bloody, milky white, etc.), transparency (leakage fluid is clear, exudate fluid is turbid), specific gravity (leakage fluid & lt;1.018, exudate fluid & gt;1.018), coagulability (leakage fluid is not easy to self-coagulation, exudate fluid is easy to self-coagulation). 2. Cytologic examination. Leaky fluid less than 100/ul, mainly lymphocytes and mesothelial cells; exudate>500/ul, neutrophils, lymphocytes or erythrocytes can be seen. 3. Biochemical examination. Including protein (leakage fluid mucin test is negative, total protein more <25g/L; exudate mucin test is positive, total protein >30g/L), glucose, lactate dehydrogenase and other items.