Diagnostic and Interventional Radiology
Abdominal Imaging - Original Article

Are the wash-out values currently accepted for lesion characterization in dedicated adrenal CT adequate for diagnosis?


Department of Radiology, Eskişehir Osmangazi University, Faculty of Medicine, Eskişehir, Turkey

Diagn Interv Radiol 2020; 1: -
Read: 140 Published: 30 October 2020

Purpose: This study aimed to investigate the accuracy of density characteristics and wash-out values of lesions detected on computed tomography (CT) at the cut-off values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference and to determine the cut-off values of parameters evaluated on CT for the differentiation of adenoma and non-adenoma lesions in the study group.

Methods: The approval of the local ethics committee was obtained. The standard adrenal CT images (consist of noncontrast, early phase [65 sec] and late phase [15 min]) and records of the 84 patients with 87 lesions that underwent adrenalectomy between January 2012-December 2018 were obtained from the record of the hospital and retrospectively reevaluated by two radiologist based on consensus. The patients were categorized as having adenoma and non-adenoma lesions according to the pathology results. The sensitivity, specificity and diagnostic accuracy of parameters (density values and wash-out percentages) were evaluated. ​It was investigated whether there was any difference in the CT parameters (size, non-contrast and early late enhancement density and absolute and relative wash-out values). The optimal cut-off values ​​for parameters evaluated on CT were determined by a ROC analysis.

Results: Non contrast CT had a specificity of 87.75% and 95.9%, sensitivity of 60% and 48.6%, diagnostic accuracy of 77.7% and 89.47% for adenomas at the cut-off value of ≤10 HU and ≤0 HU, respectively. The sensitivity, specificity and accuracy were 64.7%, 52.38% and 56.75%, respectively at the absolute wash-out value obtained as ≥ 60%, and 76.47%, 56.52% and 62.16%, respectively at the relative wash-out value obtained as ≥ 40%. There were differences between adenomas and non-adenomas of size (P < 0.0001), unenhanced attenuation (P < 0.0001), relative wash-out (P =0.020) and delay enhancement (P < 0.001). But there were no differences in terms of absolute wash-out (P = 0.230) and early enhancement (P = 0.264). The cut-off values ​​for the differentiation in terms of adenomas-non-adenomas were as follows: size ≤44 mm, non-contrast density <20 HU, early-phase density ≥ 45 HU, delayed-phase density ≤44 HU, absolute wash-out 74.83% and relative wash-out 57.76%.  

Conclusion: The current wash-out criteria used in the differentiation of adenoma and non-adenoma lesions in the dynamic CT can give false negative and positive results. According to the existing criteria, the most reliable parameter in adenoma-non adenoma differentiation is ≤ 0 HU non-contrast CT density value.

EISSN 1305-3612