Simple renal cyst: relations to age and arterial blood pressure.

Simple renal cysts are increasingly common with increasing age, as is elevated arterial blood pressure. We studied the natural history of simple renal cysts, and their possible association with arterial hypertension. Renal sonography was performed in an age- and sex-stratified random sample of 686 healthy volunteers aged 30-70 years. Eleven examinations were excluded for various reasons. One or more renal cysts measuring 10-47 mm were found in 35 individuals. The prevalence of simple renal cysts was 5.2%, ranging from 0% at age 30 to 9.7% at age 70. From the cross-sectional data it is estimated that the average renal cyst needs about 10 years to reach 20 mm in size. Mean arterial blood pressure increased with age, and was significantly higher in individuals with cysts (p = 0.0055). Closer analysis showed that the association was confined to and even stronger (p = 0.00066) for individuals with at least one cyst < or = 20 mm. We assume that smaller cysts are more likely to be totally intraparenchymal, and therefore more able to create an internal hydrostatic pressure and thus to compress the surrounding renal tissue.