Characterization of complex renal cystic masses: Comparison among CT, MRI and CEUS in the same series of patients

Introduction & Objectives: The Bosniak classification of renal cysts is commonly used by urologists and radiologists as an effective way to assess and evaluate cystic renal masses and decide clinical management. Although this classification scheme is based on computed tomographic (CT) criteria, the same approach may provide a useful framework for evaluation with magnetic resonance (MR) imaging and contrast-enhanced ultrasonography (CEUS). The aim of this study was to compare CT, MRI, and CEUS in characterization of complex renal cysts in the same series of patients. Materials & Methods: The records of patients having complex renal cysts evaluated with CT, MRI, and CEUS within a 6-months interval were considered. Inclusion criteria were at least an unenhanced and a contrast enhanced nephrographic acquisition at CT, at least T2-weighted, T1-weighted and contrast enhanced scans at MRI, and digital cine-clips available for review at CEUS. Images and clips were retrospectively evaluated by 2 blind independent readers to assigned a Bosniak score for the different techniques. This process yielded a total of 36 patients who met the inclusion criteria. ROC curve analysis was employed to assess the overall confidence for diagnosis of benign vs. malignant lesions. Reference procedure was surgery, or follow-up >3years. Results: Inter-reader agreement in assigning Bosniak score was good or very good (K values for CT, MRI, and CEUS 0.75, 0.86 and 0.79, respectively). When surgical vs. non-surgical lesions were considered, CT, MRI, and CEUS scores were equivalent in 83% of cases for reader1, and in 78% of cases for reader2. ROC curve analysis showed similar diagnostic performance for the 3 techniques (reader1 AUC=0.89, 0.96, 0.93 for and CT, MRI, CEUS, respectively; reader2 AUC=0.92, 0.98, 0.88, respectively). Conclusions: Although differences exist, CEUS, CT, and MRI are basically equivalent in characterization the majority of complex renal cysts. Concordance rates were approximately 80% with weighted good to very good k values. Differences can be useful to differentiate benign from malignant lesions in equivocal cases.