A positive nystagmus suggests that the patient has around 3,000-4,000 ml of ascites. The fluid wave tremor is a common method of checking for abdominal fluid and can be detected during a physical examination. During the examination, the patient lies flat on the hospital bed, the doctor puts the palm of one hand on the patient’s abdomen, and the other hand knocks on the opposite side of the abdomen. If there is a large amount of fluid in the abdominal cavity, the hand put on the abdominal wall will feel the fluctuation of the fluid and the impact of the sensation of fluctuation, and the fluid in the abdominal cavity can be detected when it reaches more than 3,000-4,000 ml. Positive fluid tremor, common diseases are liver disease, kidney disease, cardiovascular disease and so on. After the physical examination doctors need to carry out other tests and perform puncture and fluid extraction, laboratory tests on ascites, to find out the cause of symptomatic treatment.