A cyst of about 1.3 cm in diameter is seen in the cortical part of the left kidney, which is generally not serious if it does not affect renal function. Simple renal cysts are the most common and the least meaningful type of renal cystic disease in the clinic, and are usually not accompanied by renal hypoplasia. Most of the patients have no obvious symptoms, and most of them are found incidentally during ultrasound and other imaging examinations. It is more serious when cyst compression causes urinary tract obstruction, which puts pressure on the surrounding tissues, or when infection occurs and affects renal function. For those who are asymptomatic and have no complications, treatment is usually not needed and can be reviewed once every six months to a year. Symptomatic treatment includes controlling blood pressure, preventing and controlling cyst infection, rupture and bleeding. Cystectomy or even nephrectomy should be considered for patients with large size and malignant tendency. A cyst with a diameter of about 1.3cm can be seen in the cortex of the left kidney, which should be consulted with a doctor as soon as possible and treated under the doctor’s guidance.