Abstract:
Background The Bosniak classification of cystic renal masses (CRM) affects clinical decision-making. Most existing studies on the interobserver agreement use computed tomography (CT) images. However, magnetic resonance imaging (MRI), with its superior image resolution, soft tissue contrast, and being able to provide more detailed imaging information, is increasingly used in clinical practice.
Objective To assess the interobserver agreement on MRI images of categories Ⅱ - Ⅲ cystic renal masses (CRM) according to Bosniak classification system (2005).
Methods All CRM cases who accepted routine MRI scans or enhanced examinations in the First Medical Center of Chinese PLA General Hospital from January 2009 to December 2018, and met Bosniak Ⅱ, ⅡF and Ⅲ criteria were collected. Three radiologists independently rated the MRI images and recorded the ratings according to the Bosniak classification system. The weighted Cohen/Conger's Kappa (kw) was calculated for all cases, Bosniak categories and pathological types were served as the measurement of interobserver agreement.
Results A total of 123 CRMs from 123 patients were included. There were 84 males and 39 females, with an average age of 49.0 ± 11.1 years old. Among them, 61 (49.6%) cases had simple cyst, 15 (12.2%) cases had benign tumor and 47 (38.2%) cases with malignant tumor; 24 (19.5%) cases had Bosniak Ⅱ, 49 (39.8%) cases had Bosniak ⅡF and 50 (40.7%) cases had Bosniak Ⅲ. For all cases, the Kw was 0.43. The Kw for Ⅱ, ⅡF and Ⅲ cases was 0.05, 0.34 and 0.29, respectively, and that for simple cysts, benign tumors, and malignant tumors was 0.33, 0.16 and 0.31, respectively.
Conclusion The interobserver agreement of all Bosniak Ⅱ - Ⅲ CRMs based on MRI is moderate. The agreement for Bosniak Ⅱ is weak, that for Bosniak ⅡF and Bosniak Ⅲ are both fair. The agreement is fair for simple cysts and malignant tumors, but weak for benign tumors. The agreement for simple cysts is higher than that for the other two types of tumors.