The excretion of waste and excessive water in the body is often carried out according to different physiological needs. Some is sent, by the lung's function of activating the flow of body fluid, to the surface of the body and, is there turned into sweat. Some is changed into urine by the kidney's function of separating the clear from the turbid and removed by the urinary bladder's function of storing and excreting urine. Others are transformed into nasal mucus, saliva and tears and are removed from the nose, mouth, eyes by the functions of the corresponding organs. Also, the air exhaled by the lung bikes away some moisture.

In short, the formation, distribution and excretion of body fluid is a complicated process which needs the coordinated work of many organs. Therefore, the pathological changes in many viscera and bowels may all affect the normal metabolism of Body Fluid. For instance, an excessive loss of Body Fluid will result in its perishing. Disturbances in the transportation, distribution and excretion of " Body Fluid may cause the stagnation of water, which is manifested by phlegm retention diseases and edema. Pathological changes of Body Fluid will also affect the functions of inane viscera and bowels. For example, damage of Body Fluid and dryness of the lung cause dry cough; heart trouble caused by the retention of water is marked by palpitation; the pathological accumulation of fluid in the lung leads to dyspnea or cough. In the treatment of the above disorders, TCM always pays much attention to recuperating the lung, the spleen and the kidney, for it believes that they are key organs in maintaining the normal metabolism of water.