Fluid dark zone refers to the ultrasound examination, found that the local fluid volume has increased phenomenon, ultrasound shows liquid hypoechoic. Liquid dark area is generally the result of ultrasound examination, indicating that the amount of local liquid increased, most commonly seen in the local fluid, pus, blood and other phenomena, the specific situation is to be based on the patient’s own symptoms, as well as the size of the liquid dark area, the emergence of the time period and other comprehensive analysis and judgment. If the ultrasound detects the fluid dark area, it can not directly determine the cause, we need to further improve other auxiliary examination, under the guidance of professional doctors, combined with the comprehensive analysis of the condition, choose the appropriate treatment.