The normal kidney is 9-12cm in length, 3-4cm in width and 5-6cm in height. the kidney looks like a fava bean, although the shape is not very regular, but it is generally regarded as a rectangle, and its length, width and height are used to roughly estimate the size of the kidney, of course, the long diameter is a little more significant. The normal long diameter is 9-12cm, if it is smaller than 9cm, it is called a reduced kidney, which is seen in chronic kidney disease, such as chronic kidney failure. And greater than 12cm is called enlargement, which is more common in various acute kidney diseases, such as acute nephritis and acute progressive nephritis. Of course, some chronic kidney diseases can also cause kidney enlargement, such as diabetic nephropathy and polycystic kidney. Whether the kidney enlarges or shrinks is an abnormal state and the cause should be actively sought and intervened. Left unchecked, it may develop into chronic kidney disease or even uremic syndrome.