Round low-density shadow in left kidney may be due to various reasons such as renal cyst, renal fat hyperplasia, renal abscess or renal tumor, etc. It is necessary to pay attention to find the cause of the disease and do different treatments according to the cause of the disease, and it is recommended to seek medical treatment in time and consult a professional doctor. 1. Kidney cysts: Usually there are no symptoms, regular checkups, and generally no treatment. When cysts increase significantly or symptoms such as back pain, hematuria and infection appear, standardized treatment is needed to address the specific cause of the disease. 2. Renal fat hyperplasia: it is usually renal lipoma, and can be surgically removed when it increases in size and causes corresponding compression symptoms. 3. Kidney abscess: usually caused by bacterial infection, often accompanied by fever, renal pain, bacteriuria and other symptoms, ultrasound-guided puncture and drainage, and at the same time, the bacteriological culture of pus, to clarify the causative bacteria, according to drug sensitivity test for standard anti-infective treatment, and if necessary, feasible for surgical treatment. 4. Renal tumor: it can be seen in malignant tumors such as malignant tumor or renal carcinoma, and further enhanced CT or magnetic resonance examination can be carried out to find out the specific cause of the disease, and then proceed to the next step of treatment. Patients with rounded hypodense shadow in the left kidney are recommended to consult regular hospitals and receive standardized treatment under the guidance of physicians.