Describing the anechoic area in the ultrasound report is a diagnostic term specific to ultrasonography, where anechoic is used to describe the echogenic condition of tissues or lesions that are fluid in nature, such as water, blood, bile, cystic fluid, and leaky and exudative fluids. In ultrasound diagnosis, the most common anechoic areas are various cystic pathological changes such as hepatic cysts, renal cysts, liver abscesses, splenic abscesses, and splenic cysts. And the most common anechoic areas are pleural effusion and pericardial effusion appearing in tuberculous pleurisy, ascites appearing in advanced cirrhosis, and then there are normal fluid tissues such as cerebrospinal fluid, blood, urine, and amniotic fluid of pregnant women.