Abstract
Renal lesions encompass benign, indeterminate, primary malignant, and secondary neoplastic entities. Ultrasound frequently provides initial detection and triage, whereas CT and MRI provide complementary morphologic and tissue characterization. The Bosniak classification standardizes cystic renal masses but does not provide a unified ordinal framework encompassing solid lesions and aggressive imaging behavior. We propose a preliminary five-category Kidney Imaging Reporting and Data System (KI-RADS) integrating ultrasound, CT, MRI, and the Bosniak classification. KI-RADS 1 includes unequivocally benign lesions; KI-RADS 2 includes benign or low-suspicion lesions, including Bosniak II and IIF cysts; KI-RADS 3 comprises genuinely indeterminate lesions, including Bosniak III cysts and indeterminate solid masses; KI-RADS 4 includes lesions highly suspicious for neoplasia without convincing aggressive features; and KI-RADS 5 requires imaging evidence of aggressive local or systemic behavior. Classification is based on synthesis of relevant imaging findings rather than mandatory performance of every modality, and category assignment does not independently prescribe treatment. This conceptual framework builds on prior calls for a unified KI-RADS and requires prospective validation of reader agreement, pathology correlation, and clinical outcomes before routine implementation.