Kidney atrophy may mean the decline of kidney function, but it does not mean it is completely useless. To know the excretory function of the atrophied kidney, you can do a fractional kidney function test, which generally measures the excretory function of both sides of the kidney separately by nuclear medicine means, and can clearly know the residual kidney function of the atrophied kidney in the end. Generally, kidney atrophy occurs in common diseases, such as chronic renal failure will appear on both sides of the kidney atrophy, while for one side of the kidney atrophy is common in congenital renal dysplasia or one side of the renal artery stenosis, resulting in kidney atrophy caused by insufficient blood supply. If there is kidney atrophy, you can do split-side renal function tests as well as blood sampling for kidney function and other related tests to further evaluate the kidney.