The Growth of Renal Cysts According to the Exophytic Index of the RENAL Nephrometry Scoring System

Abstract

AIM: To investigate the growth patterns of renal cysts according to location, exophytic degree and Bosniak classificatio.

MATERIALS AND METHODS: From December 2000 to September 2012, a total of 252 patients (340 renal cysts) were included in this study. All patients had undergone computed tomography (CT) scans of the kidney level at least twice, and six months apart for any reason. Renal cyst data were assessed according to cyst side (right or left), location (upper, mid or lower), characteristics (Bosniak classification), and exophytic degree (1,2, and 3) which were stratified using the RENAL nephrometry score. The growth rate of renal cyst was analyzed according to each parameter using linear correlation analysis.

RESULTS: The mean size of renal cyst increased from 3.81 cm to 3.85 cm during a mean follow-up of 20.1 months, not significantly (p = 0.121). Among 340 renal cyst units, 180 renal cysts had an exophytic degree index of 1 (52.9%), 90 had an index 2 (26.5%), and 70 had an index of 3 (20.6%). After a mean of 20.1 months of follow-up, only exophytic degree 3 renal cysts increased in size significantly from 4.54 to 5.76 cm (p = 0.018). The annual growth rate in exophytic degree 3 renal cysts was 2.4 mm (r2 = 0.263), which was higher than that for renal cysts at other site locations. CONCLUSION: The growth rate of renal cysts varied according to exophytic location. The growth rate of exophytic renal cysts was higher than mild and moderate exophytic renal cyst.