Michael Alan Trakhtenbroit MD, Presenter: Nothing to Disclose

Benjamin G. Northcutt MD, Abstract Co-Author: Nothing to Disclose

Elliot K. Fishman MD, Abstract Co-Author: Research support, Siemens AG Advisory Board, Siemens AG Research support, General Electric Company Advisory Board, General Electric Company Co-founder, HipGraphics, Inc

Pamela Tecce Johnson MD, Abstract Co-Author: Research funded, Becton, Dickinson and Company

Recent data has shown that adrenal metastases from renal cell carcinoma may washout similar to adrenal adenoma on CT. Because the routine renal MDCT protocol includes an arterial phase acquisition, we hypothesize that additional discriminatory information can be gleaned from the CT exam if the arterial enhancement is incorporated into analysis. The purpose of this study was to determine if metastatic renal cell carcinoma can be distinguished from lipid poor adenoma by enhancement level and pattern on arterial and venous phases.

CT exams of 43 adult patients with 18 lipid poor adenomas (LPA) and 27 adrenal metastases from renal cell carcinoma (mRCC) measuring < 4 cm were reviewed retrospectively. LPA were defined as having ≥10 HU precontrast density, meeting APW and/or RPW criteria on washout CT or at least 2 years size stability, and no clinical indicators of pheochromocytoma. Renal cell metastases were confirmed by either new appearance or change in size of an adrenal mass on serial examinations in a patient with RCC. Post contrast attenuation measurements (arterial and venous phase acquisitions) and relative enhancement (arterial > venous, arterial = venous, arterial < venous) were compared. A difference of ≥ 5 HU between the arterial and venous phases was used to define a higher level of enhancement.

Average lesion size was not significantly different (mRCC 1.99 cm compared to LPA 2.34 cm, p=0.11). Mean arterial phase enhancement of the mRCC was higher than LPA (77.7 HU vs 55.4 HU respectively, p=0.02). Arterial enhancement > 100 HU was identified in 33% (9/27) of mRCC, compared to 0 adenomas. Venous enhancement levels were similar between the two lesions (mean 71.6 HU for mRCC and 71.9 HU for LPA). Nearly half of mRCC (48%, 13/27) enhanced more on the arterial phase than the venous phase, compared to 11% (2/18) of adenomas. Most adenomas (72%, 13/18) enhanced more on the venous phase, compared to 22% (6/27) of mRCC. Equal enhancement across the 2 phase was present in 30% (8/27) of mRCC and 17% of LPA (3/18).

In patients with RCC, an adrenal lesion that measures > 100 HU on the arterial phase and enhances greater on the arterial than venous phase is more likely to be a metastasis than a lipid poor adenoma.

If an adrenal lesion is identified in a patient with renal cell carcinoma, evaluation of the arterial phase can aid in distinguishing metastasis from adenoma.

Trakhtenbroit, M, Northcutt, B, Fishman, E, Johnson, P, Adrenal Gland Metastases from Renal Cell Carcinoma: Can Arterial and Venous Phase Enhancement Levels and Pattern Aid in Distinction from Lipid Poor Adenoma?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14005010.html