title: Adrenal Adenoma and Pheochromocytoma: Comparison of Multidetector CT Venous Enhancement Levels and Washout Characteristics.
abstract: OBJECTIVE
  The aim of the study was to compare multidetector CT venous enhancement level and washout characteristics of adrenal adenoma and pheochromocytoma, with the goal of defining a venous enhancement level predictive of pheochromocytoma.
  
  
  METHODS
  Retrospective review of medical records between 2002 and 2012 was performed to identify adrenal masses measuring less than 4 cm. Inclusion criteria for adrenal adenomas was venous phase contrast-enhanced computed tomography (CT), confirmatory adrenal CT (precontrast ± washout), 1 to 2 years stability, and absence of clinical indicators of pheochromocytoma. All pathologically proven pheochromocytomas with venous phase CT imaging were evaluated. Nodule size and attenuation (venous ± precontrast, delayed) were recorded. Student t test analysis compared venous enhancement levels.
  
  
  RESULTS
  One hundred eighty-three subjects with 200 adenomas were compared with 22 subjects with 26 pheochromocytomas. The mean (SD) venous enhancement level for all adenomas (58 [26] Hounsfield units [HU]) and lipid-poor adenomas (76 [25]) was lower than that of pheochromocytomas (111 [38] HU, P < 0.01). No adenomas enhanced greater than 130 HU, compared with 38% (10/26) of the pheochromocytomas. A threshold of 130 HU to identify pheochromocytoma was 38% sensitive and 100% specific for pheochromocytoma. Of the 17 pheochromocytomas with washout imaging, rapid washout was identified in all (10/10, 100%) that enhanced greater than 130 HU on the venous phase, compared with 43% (3/7) that enhanced less than 130 HU.
  
  
  CONCLUSIONS
  An indeterminate adrenal lesion that enhances greater than 130 HU on multidetector CT cannot be assumed to be an adenoma. Hypervascular pheochromocytoma (>130 HU) mimics adenoma washout pattern; absolute venous phase enhancement level must be considered.
authors.affiliation: From the Department of Radiology, Johns Hopkins Hospital, Baltimore, MD.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Northcutt
authors.forename: Michael A
authors.initials: MA
authors.lastname: Trakhtenbroit
authors.forename: Erin N
authors.initials: EN
authors.lastname: Gomez
authors.forename: Elliot K
authors.initials: EK
authors.lastname: Fishman
authors.forename: Pamela T
authors.initials: PT
authors.lastname: Johnson
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging*; D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D000311:Adrenal Glands / Q000000981:diagnostic imaging; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D010673:Pheochromocytoma / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media