Proposing Incidental-Reporting and Data System: A classification system for incidental findings in radiology

Table 1 Proposed Incidental-Reporting and Data System scoring and recommendations

I-RADS category	Description	Recommended action
I-RADS 0	Incomplete/insufficient information	Retrieve prior imaging (if not feasible, consider escalation to targeted imaging or reassignment to a higher category)
I-RADS 1	Incidental benign finding - no clinical significance	No follow-up or further work-up required
I-RADS 2	Probably benign - minimal concern	Optional follow-up (i.e., 6-12 months)
I-RADS 3	Indeterminate - moderate concern	Recommend follow-up (i.e., 3-6 months) and/or targeted imaging
I-RADS 4	Suspicious - likely pathology	Further imaging or work-up warranted
I-RADS 5	Highly suspicious - urgent concern	Immediate work-up, appropriate referral, possible biopsy
I-RADS 6	Known/confirmed pathology	No additional work-up required - continue routine or disease-specific management as applicable

I-RADS: Incidental-Reporting and Data System.

Table 2 Indicative example for each Incidental-Reporting and Data System category

I-RADS category	Indicative example
I-RADS 0	A 1.5 cm hypodense liver lesion detected on a non-contrast abdominal CT performed for suspected renal colic; a multiphase abdominal CT has been performed previously on the patient but is not available to the reporting radiologist
I-RADS 1	A simple renal cyst measuring 1.5 cm detected on abdominal CT performed due to suspected acute appendicitis
I-RADS 2	A small (3 mm) incidental pulmonary nodule detected on a cardiac CT, in a low-risk, nonsmoking patient
I-RADS 3	A 2 cm indeterminate adrenal lesion discovered incidentally on trauma CT
I-RADS 4	A 2.5 cm spiculated pulmonary nodule incidentally identified on a CT angiogram of the chest performed for suspected pulmonary embolism; morphology and margins highly concerning for malignancy
I-RADS 5	A 3.5 cm irregular mass in the pancreatic head with upstream biliary ductal dilatation, found incidentally on an abdominal MRI performed to evaluate hepatic steatosis; findings concerning for pancreatic carcinoma
I-RADS 6	Patient with biopsy-proven metastatic colon cancer and multiple known hepatic metastases, incidentally detected in the lower slices (upper abdominal slices) of a chest CT angiogram performed to exclude pulmonary embolism

These examples are illustrative and non-exhaustive and do not define strict category boundaries. Rare incidental findings (including musculoskeletal, spinal, and soft-tissue findings) should be categorized based on perceived clinical significance rather than lesion rarity. I-RADS: Incidental-Reporting and Data System; CT: Computed tomography; MRI: Magnetic resonance imaging.

Table 3 Key distinctions between the American College of Radiology incidental findings guidelines and the proposed Incidental-Reporting and Data System

Feature	ACR incidental findings guidelines	I-RADS proposal
Scope	Organ- and condition-specific	Universal, modality-agnostic, and pan-anatomical
Format	White papers and detailed flowcharts, often requiring consultation of multiple documents	Single classification system with 6 categories applicable to any incidental finding
Goal	Provide evidence-based management recommendations for specific incidental findings	Provide standardized language and structured framework to classify all incidental findings
Strengths	Evidence-based, specialty consensus; addresses details of particular lesions	Simple, unified terminology, allowing easier communication, reporting consistency, and research data harmonization
Limitations	Spread across multiple documents, not integrated into a universal framework	Broad by design, requires integration with organ-specific guidelines for detailed management
Complementarity	Offers depth for specific lesions	Provides an all-embracing framework into which ACR guidelines can be fused

The American College of Radiology guidelines offer detailed recommendations for specific organs and clinical scenarios, while Incidental-Reporting and Data System introduces a simple unifying classification system appropriate across modalities and anatomical regions. Together, they provide depth and consistency, supporting more standardized communication and incidental finding management. ACR: American College of Radiology; I-RADS: Incidental-Reporting and Data System.