title: The characterization of small hypoattenuating renal masses on contrast-enhanced CT.
abstract: OBJECTIVE
  To determine if small hypoattenuating renal masses can be characterized as simple cysts or renal cell carcinomas on contrast-enhanced computed tomography (CT).
  
  
  METHODS
  We retrospectively identified 20 small (<or=1.5 cm) hypoattenuating renal masses seen on contrast enhanced CT, consisting of 14 simple cysts and six renal cell carcinomas. Three independent readers recorded subjective visual impression (five-point scale from 1=definitely fluid to 5=definitely solid), CT attenuation, border (well circumscribed or ill defined), and shape (ovoid or irregular) for each lesion.
  
  
  RESULTS
  The overall area under the receiver operator characteristic curves for subjective visual impression, CT attenuation, border, and shape were 0.97, 0.82, 0.59, and 0.55, respectively. Using dichotomized ratings (1-2=cyst and 3-5=carcinoma), subjective impression had a sensitivity and specificity of 100% and 79-100%, respectively, for the diagnosis of renal cell carcinoma. Using a threshold of 50 Hounsfield Units (HU) or more, CT attenuation had a sensitivity and specificity of 100% and 43-64%, respectively.
  
  
  CONCLUSIONS
  Small hypoattenuating renal masses can be characterized with reasonable accuracy by subjective impression and CT attenuation; lesions that appear solid on visual inspection or have an attenuation value of 50 HU or more are likely to be renal cell carcinoma.
authors: Department of Radiology, University of California San Francisco, San Francisco, CA 94143-0628, USA.
authors: Neesha S
authors: NS
authors: Patel
authors: Liina
authors: L
authors: Poder
authors: Zhen J
authors: ZJ
authors: Wang
authors: Benjamin M
authors: BM
authors: Yeh
authors: Aliya
authors: A
authors: Qayyum
authors: Hua
authors: H
authors: Jin
authors: Fergus V
authors: FV
authors: Coakley
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging*; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007472:Iohexol; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol