[A simple renal cyst].

Incidence of simple renal cysts was calculated in 30,316 patients receiving routine ultrasound examination in one hospital, and 170 cases visiting Chiba University Hospital were further analyzed in terms of their clinical features. Incidence of simple renal cyst was 14% in all populations and ratio of male to female was 1.6:1. Patients age ranged from 8 to 92 years (average age 58.6 years) and number of a renal cyst was increased after fifth decade in both sexes. Patients of Chiba University Hospital were examined on symptoms and clinical courses with maximal follow up to 132 months (average 18 months). Symptoms associated with simple renal cysts were: none (75.3%) pain (14.7%) and gross hematuria (6.4%). Urinalysis of patients without associated urinary diseases, showed microhematuria in 40% and proteinuria in 12%, however, grade of microhematuria and proteinuria was not correlated with size of cysts. Number of cysts tended to increase with age. Size of cysts and rate of enlargement were increasing along with age. In any cases, renal function was not and affected nor occurred malignant tumor during follow-up period. Cyst punctures with sclerosing agent were performed in 16 patients, and most of the cysts remained the same as or exceeded their original size. It is concluded that routine follow-up is sufficient in most cases without symptoms, since simple renal cysts increase slowly, and impairment of renal function and progression to malignant tumors do not occur.