Risk Assessment of Incidentally Detected Complex Renal Cysts in Children: Potential Role for a Modification of the Bosniak Classification

Abstract

Incidentally detected complex renal cysts in children are a rare but worrisome occurrence due to the perceived potential risk of malignancy. We examined the natural history of such cysts in a cohort of children. We obtained access to a database containing all radiology reports generated at a single institution from 1996 to 2004. We used key words to limit our search, subsequently reviewing charts and images to confirm the diagnosis of a complex renal cyst and to collect clinical data. Cases were categorized according to a modification of the Bosniak classification, using ultrasound in most patients and computerized tomography or magnetic resonance imaging when available. Complex renal cysts were identified in 39 children. Mean patient age at presentation was 7 years. Mean cyst size was 1.6 cm. A total of 18 cases diagnosed by ultrasound only were observed with serial imaging. Additional contrast enhanced computerized tomography or magnetic resonance imaging was performed in 21 of 39 patients (54%). Surgical resection was performed in 5 patients and pathological evaluation revealed benign cyst in 3 (modified Bosniak class II in 2 patients and class III in 1) and renal cell carcinoma in 2 (III in 1 and IV in 1). All other patients had modified Bosniak class II cysts, which remained essentially unchanged during a mean followup of 26.8 months (range 9 to 70). While not validated in children, our data suggest the modified Bosniak classification appears useful as a guideline to direct the management of complex renal cysts in the pediatric population.