title: Renal Masses With Equivocal Enhancement at CT: Characterization With Contrast-Enhanced Ultrasound.
abstract: OBJECTIVE
  The purpose of this article is to retrospectively investigate in two radiology centers the role of contrast-enhanced ultrasound in the characterization of renal masses with equivocal enhancement at CT (i.e., with a density increase of 10-20 HU between unenhanced and contrast-enhanced scans) not characterized with conventional ultrasound modes.
  
  
  METHODS
  Forty-seven renal lesions (range, 0.8-7.7 cm; average, 2.6 cm) with equivocal enhancement at CT underwent contrast-enhanced ultrasound using sulfur hexafluoride-filled microbubbles. Examinations were digitally recorded for retrospective blinded evaluation by two radiologists with 20 and 10 years' experience in urologic imaging. Histologic results were available for 30 of 47 (64%) lesions (25 primary malignant tumors, two metastases, and three primary benign lesions). Two lesions increased in size and complexity during the follow-up and were considered malignant. One Bosniak category III and 14 category IIF cysts were stable after a follow-up of at least 3 years and were considered benign. ROC curve analysis was used to assess the capability of contrast-enhanced ultrasound to differentiate benign from malignant lesions.
  
  
  RESULTS
  Twelve likely complex cystic lesions at gray-scale ultrasound were cystic also on contrast-enhanced ultrasound and reference procedures. Eleven of 34 lesions that appeared solid at gray-scale ultrasound were cystic on contrast-enhanced ultrasound and reference procedures. One lesion considered likely solid by one radiologist and possibly cystic by the other was a solid tumor at contrast-enhanced ultrasound and histologic analysis. The diagnostic performance of contrast-enhanced ultrasound to characterize the lesions as benign or malignant was high for both readers (AUC, 0.958 and 0.966, respectively).
  
  
  CONCLUSIONS
  Contrast-enhanced ultrasound is effective for characterizing renal lesions presenting with equivocal enhancement at CT.
authors.affiliation: 1 Department of Radiology, University of Trieste, Strada di Fiume 447, Trieste 34149, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Bertolotto
authors.forename: Calogero
authors.initials: C
authors.lastname: Cicero
authors.forename: Rosaria
authors.initials: R
authors.lastname: Perrone
authors.forename: Ferruccio
authors.initials: F
authors.lastname: Degrassi
authors.forename: Francesca
authors.initials: F
authors.lastname: Cacciato
authors.forename: Maria A
authors.initials: MA
authors.lastname: Cova
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010743:Phospholipids; D012189:Retrospective Studies; D013459:Sulfur Hexafluoride; D014057:Tomography, X-Ray Computed; D018615:Ultrasonography, Doppler, Color
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride
keywords: characterization; contrast-enhanced ultrasound; equivocal enhancement; renal CT; renal masses