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RUN Clinical Quiz 0611
A 55-year-old woman with history of hypertension, melanoma, and urolithiasis is found to have a left adrenal mass on a non-contrast computed tomography (CT) scan evaluation obtained to assess renal colic.
The mass measures 2.5 cm in diameter and demonstrates an attenuation of 30 Hounsfield units (HU). A metabolic work-up rules out hypercortisolemia and hyperaldosteronemia. Plasma free metanephrines are within normal limits, excluding the possibility of pheochromocytoma.
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C: The goal of adrenal imaging is to differentiate benign adrenal adenomas from other adrenal lesions. Some 70% of adenomas are lipid-rich and exhibit low-density attenuation on non-contrast CT. In fact, an adrenal lesion that is less than 10 HU in density on non-contrast CT can be deemed an adenoma with an extremely high degree of certainty.1 Approximately 30% of adenomas, as in the above example, are lipid-poor and exhibit an attenuation of greater than 10 HU on non-contrast CT.2-4 For these lipid-poor adrenal lesions, there is a temptation to obtain an MR study for better characterization; however, adrenal protocol MR—which harnesses opposed phase chemical-shift strategies to quantify intracellular lipid within adrenal lesions—is only marginally superior to non-contrast CT in identifying adenomas.5, 6 As such, the go-to study for a lipid-poor adrenal lesion is a 15-minute CT washout study. Adrenal masses that “washout,” or lose more than 40%-60% of contrast enhancement 15 minutes after the contrast bolus, are managed as adenomas, since the specificity of an adrenal washout study is extremely high.2-4, 7 An adrenal washout calculator can be found at www.cancernomograms.com. Gadolinium contrast agents do not exhibit the same washout properties as does iodinated contrast. Thus, CT washout is a far superior study for characterizing adrenal lesions than MR imaging.8 Regardless of radiographic characteristics, every adrenal lesion requires an appropriate metablic work-up.9
The case was prepared by Alexander Kutikov, MD, of Fox Chase Cancer Center in Philadelphia.
References
1. Grumbach, MM, Biller BMK, Braunstein GD, et al. Management of the clinically inapparent adrenal mass (“Incidentaloma”). Ann Intern Med. 2003;138:424-429.
2. Szolar, DH, Korobkin M, Reittner P, et al. Adrenocortical carcinomas and adrenal pheochromocytomas: Mass and enhancement loss evaluation at delayed contrast-enhanced CT. Radiology. 2005;234:479-485.
3. Korobkin M, Brodeur FJ, Francis IR, et al. CT time-attenuation washout curves of adrenal adenomas and nonadenomas. Am J Roentgenol. 1998;170:747-752.
4. Pena CS, Boland GWL, Hahn PF, et al. Characterization of indeterminate (lipid-poor) adrenal masses: Use of washout characteristics at contrast-enhanced CT. Radiology. 2000;217:798-802.
5. Israel GM, Korobkin M, Wang C, et al. Comparison of unenhanced CT and chemical shift MRI in evaluating lipid-rich adrenal adenomas. Am J Roentgenol. 2004;183:215-219.
6. Haider MA, Ghai S, Jhaveri K, et al. Chemical shift MR imaging of hyperattenuating (>10 HU) adrenal masses: Does it still have a role? Radiology. 2004;231:711-716.
7. Boland GW, Blake MA, Hahn PF, et al. Incidental adrenal lesions: principles, techniques, and algorithms for imaging characterization. Radiology. 2008;249:756-775.
8. Hussain HK, Korobkin M. MR imaging of the adrenal glands. Magn Reson Imaging Clin N Am. 2004;12:515-544.
9. Kutikov A, Crispen PL, Uzzo RG. Pathophysiology, evaluation, and medical management of adrenal disorders. In: Campbell-Walsh Urology, 10th ed. Edited by A. J. Wein, L. R. Kavoussi, A. W. Partin et al. Philadelphia: Elsevier, p. in press, 2011
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