Left renal malformation tumor, also known as left renal vascular smooth muscle lipoma, is a common benign tumor of the kidney. As the name implies, it is composed of three components: blood vessels, smooth muscle and fat, and is most likely to occur in women aged 40-60. Ultrasound has the advantage of being inexpensive and non-invasive and can be the first choice for examination. CT examination has specificity and can confirm the diagnosis when a negative CT value of fat is found. In general, most smaller renal malformations are asymptomatic and slow-growing, and most are detected by ultrasound during health checkups. Renal malformation tumors smaller than 5 cm or without clinical symptoms can be observed regularly and reviewed every six months. For renal malformation tumors larger than 5 cm or with pain and discomfort in the lower back and abdomen, surgery is recommended to prevent spontaneous rupture and bleeding.