Quantitative enhancement washout analysis of solid cortical renal masses using multidetector computed tomography

Purpose: The aim of the study was to prospectively assess the utility of quantitative enhancement washout method in the differentiation of benign solid renal masses from various subtypes of malignant masses using multidetector computed tomography. Methods: In a prospective investigation from January 2009 to May 2010, 97 patients with solid renal masses underwent CT scan examination with unenhanced, arterial, parenchymal, and delayed phases. The following features were analyzed: the maximum attenuation value in each phase, attenuation difference (enhancement) of the mass in each phase from the unenhanced phase (ΔH), and parenchymal and delayed phases' washout. Of these patients, 82 (85%) underwent unilateral radical nephrectomy, 15 (15%) underwent partial nephrectomy. Group comparison was performed with the Kruskal-Wallis test and Mann-Whitney U test. Results: The masses included in our study were 45 clear cell renal cell carcinomas (CCRCCs); 18 chromophobe renal cell carcinomas, 16 papillary (PRCC), 14 oncocytomas, and 4 poor fat containing angiomyolipomas. In the arterial phase, the CCRCC was the most enhancing type and could be differentiated from other renal masses (benign or malignant) with high sensitivity and specificity. In the parenchymal phase, the CCRCCs demonstrated the highest washout. Chromophobe renal cell carcinomas showed the second highest washout in this phase. Benign renal cell carcinomas and PRCCs did not exhibit significant washout in this phase.In the delayed phase, the malignant lesions (with the exception of PRCCs) showed the highest washout. Benign lesions showed significant washout but less than malignant lesions. Conclusions: Multiphasic multidetector CT utilizing arterial-phase attenuation and quantitative enhancement washout method could help in the preoperative differentiation of various types of solid renal masses.