AB025. SOH26AB_0262. Diagnostic accuracy of MRI versus CT for differentiating malignant and benign adrenal incidentalomas: a systematic review

Background: Adrenal masses are incidentally identified (adrenal incidentalomas) in about 5% of cross-sectional abdominal imaging conducted for non-adrenal indications. The frequent use of serial and multi-modality imaging in the evaluation of adrenal incidentalomas contributes substantially to healthcare costs and can be burdensome for patients. Clear guidance is required to determine the most appropriate imaging modality for characterising incidental adrenal lesions.

Methods: A structured literature search of PubMed, Turning Research into Practice (TRIP), Embase, and Cochrane Library was undertaken to identify systematic reviews, meta-analyses, and comparative diagnostic studies assessing magnetic resonance imaging (MRI) versus computed tomography (CT) in adrenal incidentalomas. Evidence was screened for study quality, applicability, and diagnostic accuracy outcomes to determine the highest-level data informing imaging practice.

Results: The search identified a substantial body of literature, with two high-quality systematic reviews providing the most rigorous evidence. CT demonstrated consistently robust diagnostic accuracy, with unenhanced attenuation ≤10 Hounsfield units (HU) serving as a reliable criterion for excluding malignancy, and adrenal washout CT offering additional discriminatory value when appropriately applied. In contrast, MRI performance, though promising, was supported by smaller and methodologically heterogeneous studies, reducing confidence in pooled estimates. Overall, CT remains the better-supported modality, with insufficient evidence to establish MRI superiority.

Conclusions: Current evidence indicates that CT provides the most reliable and well-validated criteria for excluding malignancy in adrenal incidentalomas, with both unenhanced attenuation thresholds and adrenal washout protocols contributing valuable diagnostic information. Although MRI provides complementary insights, its performance is supported by less robust and more heterogeneous data. Optimizing imaging pathways by prioritizing high-value tests may reduce unnecessary investigations, lower costs, and streamline patient management.

Keywords: Adrenal incidentaloma; computed tomography (CT); diagnostic accuracy; diagnostic imaging; magnetic resonance imaging (MRI)