Adrenal washout CT in patients with no history of cancer: a waste of time?

Abstract

PurposeTo validate the diagnostic performance of adrenal washout CT in patients without known malignancy in a Western Australian population.MethodsA radiology information system (RIS) search for CT reports containing “adrenal” and “washout” across six networked metropolitan public hospitals between January 2005 and November 2021. Homogenous nodules ≥ 1 cm, ≥ 10 HU without a suspected functional component in patients without a history of malignancy were included. Reported absolute and relative washout percentages were recorded and re-measured from unenhanced, 60-s portal venous and 15-min delayed phase imaging and compared to either histopathological or CT follow up for growth (≥ 12 months) reference standards.Results2653 studies were screened with 191 meeting inclusion criteria. 105 nodules underwent washout CT and then had either histopathological (12 patients) or CT follow up (93 patients) reference standards available.Reported absolute washout (aWO) estimated sensitivity and specificity for malignant/indeterminate nodules was low at 33% (95% CI 25–43%) and 77% (95% CI 68–84%) respectively. Reported relative washout (rWO) sensitivity and specificity were 56% (95% CI 46–65%) and 69% (95% CI 60–77%) respectively. Negative predictive values for both aWO and rWO were reassuring at 92% (95% CI 86–96%) and 94% (95%CI 88–97%).ConclusionOur study validates a recent report suggesting that adrenal washout has poor sensitivity for and consequent limited utility to exclude malignancy in patients with no cancer history. However, patients with incidental adrenal nodules < 4 cm in size with benign washout can be reassured by the high negative predictive value and worked up to exclude functional adenoma and re-imaged in a year to confirm no growth.Graphical