Age-related occurrence of simple renal cysts studied by ultrasonography.

Three hundred forty-eight outpatients without evidence of renal disease were examined by ultrasound. Their ages ranged from 18 to 83 years. Unexpected renal cysts of more than 1 cm were found in 47 patients (13.5%). No cysts were demonstrated in patients less than 23 years old; thereafter the number of patients with cysts increased significantly with age. The cyst diameter also tended to increase with age, but the correlation with age was not significant. There was no statistical difference of cyst occurrence between the right and left kidney, or between males and females. The upper portion of the kidney was most often affected in the equally divided three portions along the long axis. These results confirm that the development of simple renal cysts is age-related.