Ultrasound examination of kidneys is mainly to exclude kidney stones, kidney tumors, hydronephrosis, polycystic kidneys and to determine whether the kidneys are enlarged or shrunken, ultrasound examination is a frequently used examination method in nephrology, which is particularly effective in determining the structure, size and whether there are any long lesions in the kidneys. Kidney stones can be seen as strong echoes under ultrasound, while hydronephrosis can be seen as dilated renal pelvis and separated collecting system through ultrasound, and polycystic kidney can be shown as non-echoic and multiple in ultrasound. The normal kidney length is 9-12cm, and if it is smaller than 9cm, it is called shrinkage, and if it is larger than 12cm, it is called enlargement. The former is mainly seen in renal atrophy, while the latter is mainly seen in acute nephritis, acute nephritis, polycystic kidney, etc. Therefore, it is recommended to have an ultrasound examination when the above mentioned lesions are suspected in the kidney.