CT colonography reporting and data system

Last revised by Andrew Murphy on 23 Mar 2023

CT Colonography Reporting and Data System (C-RADS) is a method devised to standardize CT colonography reporting.


It primarily classifies abnormalities into colonic (C) and extra-colonic (E).

Colonic classification
  • C0: inadequate study
  • C1: normal colon/benign lesion: routine screening to be continued
  • C2: indeterminate polyp: surveillance or colonoscopy
    • 6-9 mm in diameter
    • <3 in number
  • C3: possibly advanced adenoma: follow up colonoscopy
    • >10 mm in diameter
    • >3 in number with each 6-9 mm
  • C4: colonic mass likely malignant: urgent surgical referral
    • has associated luminal narrowing
    • has extra-colonic extension
Extra-colonic classification
  • E0: limited exam
  • E1: normal exam or normal variant
  • E2: clinically unimportant finding, e.g. simple liver cyst, vertebral hemangioma: no work up required
  • E3: likely unimportant or incompletely characterized finding, e.g. minimally complex renal cyst: referral depends on local center
  • E4: potentially important finding, e.g. solid renal mass, abdominal aortic aneurysm 3: communicate to referring physician

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Cases and figures

  • Case 1: normal colonography
    Drag here to reorder.
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