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

IntroductionMost 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 workTo 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 methodsSixty-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.ResultsThe detected incidentalomas included 46 adenomas and 18 non-adenomas. The accuracy of the RPW at a washout threshold of ⩾40% was 98.9%, and the accuracy of APW at a washout threshold of ⩾60% was 99%.ConclusionThe 15-min delayed washout MDCT could be a valuable diagnostic tool in adrenal incidentalomas. At APW ⩾60% and RPW ⩾40%, it is significantly accurate in differentiating adrenal adenomatous lesions.