It is very common to have renal cysts, especially as you get older. Your cyst is very small and not something to worry about. However, size is not the most important thing. Cysts are categorized by their degree of complexity, using Bosniak classification system. In general, no follow up is necessary for simple cysts or minimally complex cysts containing thin septations. Also, no follow up is necessary for hemorrhagic and/or proteinaceous cysts measuring less than 3 cm. On the other hand, cysts with thick septations, nodularity, and/or enhancement have higher risk for malignancy.