The natural history of simple renal cysts in adults

Abstract

Purpose: Simple renal cysts are common in older patients and they are usually left untreated, yet only a few studies have been done on the natural history of simple renal cysts. We investigated the sequential changes in their size and number in 103 patients. Materials and Methods: From January 1993 to August 2003, we followed 103 patients who were suffering with simple renal cysts. Their mean age was 55.8±18.72 years old (M:F=58:51). Using Abdominal USG and CT, the annual changes in renal cysts were analyzed through the follow-up period, and the mean follow-up period was 52.3±17.58 months. The values of the parameters were compared with using a 2-tailed Student's t-test, multivariate logistic regression analysis and the chi-square test. Results: At the time of diagnosis, the mean number and size of simple renal cyst were 1.5±1.31 cysts per each kidney and 25.3±12.42mm, respectively. On the consecutive imaging study, the size of the renal cysts was increased 4.4±1.54mm per year. The average size increase was significantly greater in the individuals younger than 50 versus the patients 50 years or older (5.7±2.14mm /year vs 3.7±1.45mm/year, respectively). The multiple cysts showed a significantly larger size increase than did the single cysts (8.1±3.27mm/year vs 3.6±1.64mm/year, respectively). The size increase of the bilateral renal cysts was significantly larger than that of the unilateral renal cysts (5.6±1.48mm/year vs 4.1±1.02mm/year, respectively). No significant difference was observed for the average size increase with regard to gender or the initial cyst size. Only the number of cysts was a significant predictor of aggressiveness on the multivariate logistic regression analysis. Conclusions: The simple renal cysts progress in size and they appear to grow with aging. They seem to grow more rapidly in patients with a younger age, and for multiple and bilateral renal cysts.