Renal cysts are a common radiological finding in both adults and children. They 
occur in a variety of conditions, and the clinical presentation, management, and 
prognosis varies widely. In this article, we discuss the major causes of renal 
cysts in children and adults with a particular focus on the most common genetic 
forms. Many cystoproteins have been localized to the cilia centrosome complex 
(CCC). We consider the evidence for a universal 'cilia hypothesis' for cyst 
formation and the evidence for non-ciliary proteins in cyst formation.