A clinical view of simple and complex renal cysts.

The availability and use of abdominal diagnostic ultrasonography or computed tomography has led to the frequent detection of asymptomatic renal cysts. The vast majority of these are simple cysts that are usually unilateral and solitary with well-defined structural and imaging features and whose occurrence, number, and bilaterality increase with age. Simple cysts are asymptomatic, except when complications such as hemorrhage, infection, or rupture lead to the development of complex cysts with calcification, demarcation irregularities, and multilobularity. The diagnostic challenges that cysts present are in the differentiation of the less common complicated complex cysts from those associated with malignancy and when numerous the possible heralding of genetic or acquired multicystic diseases of the kidney.