The causes that can cause left kidney cyst are as follows: 1. Genetic factors, acquired cysts usually do not occur hereditary, but congenital polycystic kidney is mostly related to genetic factors. Children show autosomal recessive inheritance, mostly in childhood onset, progressive kidney function destruction can affect life safety. Adults tend to have autosomal dominant inheritance and develop the disease in adulthood, after which the disease progresses slowly and progressive renal destruction may occur. In severe cases, kidney dialysis or kidney transplantation is required.2. Acquired cysts may develop due to renal tubular diverticula, various factors lead to renal tubular lesions, so that the formation of diverticula or glomerular filtration of primary urine, can not be discharged through the renal tubules, resulting in the formation of cysts of different sizes, and with the aggravation of tubular obstruction, the cysts gradually expand and increase in size, and then cause compressive symptoms or painful symptoms.