Diagnostic value of delayed washout rate of contrast-enhanced multi-detector computed tomography in adrenal incidentalomas

Abstract

Introduction: Most adrenal incidentalomas are benign non-hyperfunctioning adenomas which can be categorized as lipid-rich or lipid-poor. An adrenal CT post-contrast delayed washout study may differentiate adenomas from other adrenal neoplasms.
Aim of the work: To evaluate the role of MDCT in detecting adrenal incidentalomas with assessment of the diagnostic value of 15-min delayed washout rate in the differentiation of these incidentally detected adrenal lesions.
Materials and methods: Sixty-four patients with adrenal incidentaloma were enrolled in this study that was carried out in the period from January 2010 to January 2013. The mean attenuation values of adrenal masses were measured in the pre-contrast, post-contrast venous and delayed enhanced phases in addition to estimation of 15-min delayed washout rate. The relative percentage washout (RPW) and absolute percentage washout (APW) values were calculated. The receiver operating characteristic (ROC) curve analysis was performed to evaluate the accuracy of different MDCT phases at optimal cut-off values for diagnosis of adrenal incidentalomas.
Results: The detected incidentalomas included 46 adenomas and 18 non-adenomas. The accuracy of the RPW at a washout threshold of P40% was 98.9%, and the accuracy of APW at a washout threshold of P60% was 99%. 
Conclusion: The 15-min delayed washout MDCT could be a valuable diagnostic tool in adrenal incidentalomas. At APW P60% and RPW P40%, it is significantly accurate in differentiating adrenal adenomatous lesions.

KEYWORDS Washout; Multi-detector computed tomography; Adrenal incidentalomas