Renal oncocytoma: Is URO‐CT useful in histological diagnosis?

IntroductionOver the past few years, the increasing use of cross‐sectional imaging, including ultrasound and computed tomography imaging, resulted in an increase incidental diagnosis of renal tumors, especially small renal masses (<4cm). The knowledge that 30% of these masses may be benign, including oncocytomas led to the investigation for more effective methods of diagnosis in order to avoid overtreatment situations.ObjectivesThe authors decided to analyse and compare contrast enhancement patterns of oncocytomas and clear‐cell renal cell carcinoma (ccRCC) to predict histology.Material and methodsBetween 2004‐2015 we retrospectively identified 32 patients with either histological confirmation of renal oncocytoma (N=16) or ccRCC (N=16) who underwent percutaneous biopsy, total or partial nephrectomy. The relative attenuation of solid renal lesions and normal renal cortex was determined in the unenhanced and nephrographic phase. Statistical comparison was carried out by Mann‐Withney test.ResultsThe oncocytomas and cc‐RCC average size was 3.7cm [1.8 to 14] and 3.5cm [1.9 to 8.4], respectively. The average attenuation in the unenhanced phase was 33HU and 32HU, respectively. In nephrographic phase, the average contrast enhancement was 47.5 and 47.4H, respectively. In nephrographic phase, the attenuation difference between the oncocytomas and normal renal cortex was 43.5HU and the attenuation difference between the cc‐RCC and normal renal cortex was 59.7HU. These results were statistically significant (p<0.05).ConclusionsIn the nephrographic phase, URO‐CT reveals that oncocytomas have greater isodensity to the normal renal cortex compared to cc‐RCC. This finding can help us to determine which lesions we should biopsy or not.