CT Colonography Reporting and Data System (C-RADS) is a method for standardizing CT colonography (CTC) reporting. The current revision is 2023 5.
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Terminology
A polyp is defined as a homogenous soft tissue attenuation lesion projecting into the colonic lumen with a fixed point of attachment to the wall. Polyps at CTC are typically ≥6 mm or larger 5.
A mass is defined as a lesion measuring ≥30 mm and should not be described as a polyp 5.
Recommended descriptors of a colonic lesion at CTC include 5:
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attenuation
soft tissue
fat (lipoma, fibrolipoma, inverted diverticulum)
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morphology
sessile (broad-based)
pedunculated (polyp with separate stalk)
flat or laterally spreading tumors
mass (≥30 mm)
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size (single largest dimension)
large (≥10 mm)
small (6-9 mm)
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diminutive (≤5 mm)
not typically reported
much more likely to represent adherent stool, hyperplastic polyp (no malignant potential) or tubular adenomas
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location - six standard colonic segments:
Classification
Abnormalities are classified into colonic (C) and extra-colonic (E).
Colonic classification
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C0: inadequate study and/or awaiting prior comparisons
inadequate preparation: fluid or feces obscures exclusion of lesions ≥10 mm
inadequate insufflation: one or more colonic segments collapsed on both views
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C1: normal colon/benign lesion
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continue routine screening
no abnormality
no polyp ≥6 mm
lipoma, inverted diverticulum or other non-neoplastic findings
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C2a: indeterminate polyp or indeterminate finding
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repeat CTC in 3 years or colonoscopy
6-9 mm polyp
<3 in number
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C2b: likely benign diverticular finding
likely benign: repeat CTC in 5 years, or;
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uncertain benign: repeat CTC in 3 years
mass-like area such as diverticular mycosis coli, muscular hypertrophy or structure
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C3: possibly advanced adenoma
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follow up colonoscopy
polyp ≥10 mm
≥3 polyps 6-9 mm size
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C4: likely malignant colonic mass
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colonoscopy, surgical and/or oncology referral
polypoid or malignant-appearing mass ≥30 mm
lesion compromises bowel lumen or extra colonic invasion
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Extra-colonic classification
The purpose of CTC is to identify pre-malignant or malignant colonic lesions. The extra-colonic classification aims to simplify communication of incidental findings external to the colon. Since the original 2005 version, the updated 2023 version has reduced the number of categories from 5 to 4, combining E1 and E2, with reporting of E0 now optional 5.
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E0: examination inadequate for assessment
reporting of this category is optional
E1/E2: no clinically important, or stable previously known extra-colonic findings, not requiring further work-up
E3: likely clinically unimportant finding; further work-up may be warranted
E4: likely clinically important finding; further work-up needed
Treatment and prognosis
Suggested management 5:
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diminutive polyps (≤5 mm)
risk of advanced adenoma is 1.7%
CTC guidelines do not mandate reporting of this size as non-reporting has been found to be cost-effective and safe
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small polyps (6-9 mm)
risk of advanced adenoma is 6.6%
polypectomy is suggested for patients who are candidates for colonoscopy
in patients with 1-2 small polyps, follow-up at 3 years is also an option depending on age and comorbidities
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large polyps (≥10 mm)
risk of advanced adenoma is 30.6% with increased rates of high-grade dysplasia (5-10%) and carcinoma (1-3%)
referral for colonoscopy and polypectomy is recommended
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masses (≥30 mm)
sensitivity and specificity of CTC for detection of colonic masses approaches 100%
referral for colonoscopy or directly to surgery or oncology is recommended
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screening interval
5-year screening interval is recommended by the American Cancer Society and the United States Preventative Task Force
5-year screening interval is shown to be comparable to colonoscopy
Practical points
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evaluation using both 2D and 3D reconstructions are recommended to improve polyp detection 5
2D imaging includes traditional multiplanar reconstructions
3D reconstructions could include endoluminal perspective, anatomic dissection views, perspective filet or unfolded cube