BERKELEY, CA (UroToday.com) - This study out of Toronto’s Hospital for Sick Children evaluated the natural history of complex renal cysts in children.

The group identified patients with a known history of a complex renal cyst. To capture the maximum number of patients they searched the database of all radiologic reports from their institution between 1996 and 2004. The group then reviewed the charts of these patients and images to confirm the diagnosis of a complex renal cyst. Children with evidence of cystic kidney disease, prior renal trauma, previous renal surgery, or intervention or any amount of insufficient data were excluded from further reviews. Cases were categorized according a modification of the Bosniak classification using ultrasound in most patients and CT or magnetic resonance imaging when available.

The group found that complex renal cysts were identified in 39 children. Mean patient age of presentation was 7 years. Mean cyst size was 1.6 cm. A total of 18 cases diagnosed by ultrasound were only observed with serial imaging. Additional contrast enhanced CT or MRI studies were performed in 21 of the 39 patients. 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). The other 2 patients had renal cell carcinomas and they were both diagnosed as a III and a Bosniak I. All the other patients had the new modified Bosniak class II cysts which remained essentially unchanged during a mean follow-up of just over 2 years. The range of the follow up was 9 months to 70 months.

The group also found in their series that it was apparent that ultrasound imaging was more sensitive than CT at detecting septations. They state that CT is currently the modality of choice for imaging complex renal cysts in adults, but recently there have been legitimate concerns raised with regard to the long term implications of radiation exposure in children.

One important limitation in this study was that the follow up is short. They also had patients that were just evaluated radiographically and had no urologist involved. They do bring up the fact that these limitations are apparent and believe that a contrast enhanced axial imaging is warranted in children with ultrasound findings of a Bosniak III or IV. If these findings are confirmed on CT or MRI they recommend surgical resection of the lesion. As a rough guideline they recommend performing ultrasound at 3-6 month intervals in the first year and then annually once the cyst has been deemed stable in all patients with Bosniak class II cysts. They currently have no recommendations for a Bosniak class II F in their series and state that is the reason why they left it out of their classifications for their patients.

M. Chad Wallis, Armando J. Lorenzo, Walid A. Farhat, Darius J. Bägli, Antoine E. Khoury and Joao L. Pippi Salle.

J Urol. 2008 Jul;180(1):317-21
10.1016/j.juro.2008.03.063

PubMed Abstract
PMID: 18499167

UroToday.com Pediatric Urology Section

Written by Pasquale Casale, MD, a Contributing Editor with UroToday.

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