Factors associated with diagnostic accuracy when performing a preablation renal biopsy

Long-term treatment of patients undergoing definitive management of a small renal mass depends largely on the final pathology determination. Preablation renal biopsy (PABx) is often the only source of determining pathology in patients undergoing thermal ablation of a small renal mass. We sought to evaluate patient and tumor characteristics that may play a role in determining the accuracy of a PABx obtained during radiofrequency ablation (RFA).

This retrospective study included a review of our prospectively collected database of all laparoscopic and CT-guided RFA (LRFA; CTRFA) performed in our center from November 2001 to July 2013. Three 18-gauge core biopsies were obtained per tumor. Pathology samples were stratified into diagnostic (group 1) and nondiagnostic (ND) (group 2). We used univariate and multivariate analysis to identify potential biopsy result-modifying factors including patient characteristics (age, body mass index [BMI]), biopsy approach (CTRFA vs LRFA), tumor size, orientation, depth, and polarity.

A total of 463 treatments in 411 patients were evaluated. Of these, 66% were CTRFA while 34% were LRFA. Mean patient age was 67.4 years (31-88), mean BMI was 28.3 kg/m(2) (16.6-47.2), and mean tumor size was 2.6 cm (0.3-5.5). There was a total of 73 (15.8%) ND biopsies. On multivariate analysis, CTRFA and medial tumors managed with either CTRFA or LRFA were found to be associated with an increased likelihood of a ND biopsy.

PABx obtained in patients undergoing CTRFA and from medial tumors managed with either CTRFA or LRFA were more likely to be ND. Future RFA patients should be counseled appropriately. Additional biopsy cores may be needed in these subgroups. Further prospective studies are warranted to confirm these findings.