Abstract : Objective - To investigate the safety profile of percutaneous cryoablation of renal tumours < 7 cm, utilising data extracted from an international multicentre registry. Materials and methods - A retrospective review of all immediate and delayed complications from a multicentre database was performed and was categorised according to the Clavien-Dindo classification. Statistical analysis was performed for both overall complications (all Clavien-Dindo) and major complications (Clavien-Dindo 3 to 5). The following criteria were identified as potential predictive factors for complications: centre number, modality of image guidance, tumour size (≤ 4 cm vs. > 4 cm), number of tumours treated in the same session (1 vs. > 1) and tumour histology. Results - A total of 713 renal tumours underwent ablation in 647 individual sessions. In 596 of the cases, one tumour was treated; in the remaining 51 cases, several tumours were treated per session. Mean lesion size was 2.8 cm. Fifty-four complications (Clavien-Dindo 1 to 5) occurred as a result of the 647 procedures, corresponding to an overall complication rate of 8.3%. The most frequent complication was bleeding (3.2%), with 9 cases (1.4%) requiring subsequent treatment. The rate of major complication was 3.4%. The only statistically significant prognostic factor for a major complication was a tumour size > 4 cm. Conclusion - Percutaneous renal cryoablation is associated with a low rate of complications. Tumours measuring more than 4 cm are associated with a higher risk of major complications. Key points - • Percutaneous kidney cryoablation has a low rate of complications. • Bleeding is the most frequent complication. • A tumour size superior to 4 cm is a predictive factor of major complication.
