Left renal smooth muscle lipoma, which is a benign tumor of the kidney, can be clearly diagnosed mostly by ultrasound or CT. Usually the imaging shows a solid tumor of the kidney with low density components, such as adipose tissue, which can be differentiated by enhanced CT. Smooth muscle lipoma of the kidney is a benign tumor. If the tumor is <4cm, regular outpatient review is recommended. If symptoms such as back pain or hematuria occur, hospitalization for surgery is recommended. Even if there is no symptom, when the size of tumor is >4cm or more, it is recommended to be hospitalized for surgery. When the tumor grows larger, it may produce local compression symptoms, destroy the kidney parenchyma and affect the kidney function. As the size increases, bleeding and necrosis may occur. Some patients may have symptoms of acute back pain caused by rupture of renal malformation tumor on its own, so surgery is recommended.