Under normal circumstances, the kidney is normal in shape and will not shrink in volume. If one kidney shrinks, it means that there is a possibility of renal artery stenosis. The common cause is renal artery atherosclerosis, some of which are related to large artery inflammation and fibromuscular dysplasia. In addition, congenital renal dysplasia, renal tuberculosis, chronic pyelonephritis, renal contusion, etc. can also cause atrophy of one kidney. After atrophy of one kidney, only the other kidney can excrete water and filter toxins. The normal kidney plays a role, while the atrophied kidney does not, resulting in decreased renal function. The patient shows fatigue, back pain, edema, and increased blood creatinine.