C-RADS ™ v. 2023

ACR's CT Colonography Imaging Reporting & Data System, for describing colorectal and extra-colonic findings - Version 2023 (released January 2024)

C-RADS

Colonic findings

Is any of the following true about this study?

C0 = Inadequate Study

Repeat CTC or consider an alternative screening test if inadequate.

C0 = Awaiting prior comparisons

Amend when prior studies are available.
Which abnormalities have you identified? (select all that apply)

C1 = Normal Colon or Benign Lesion

Recommendation: Continue routine screening every 5-10 years

C2a = Intermediate Polyp or Indeterminate Finding

Recommendation: Repeat CTC in 3y or colonoscopy. For polyps 6 mm and greater, recommend polypectomy in suitable patients versus follow-up study in 3 years, subject to individual patient circumstance.

C2b = Likely benign diverticular finding

Likely benign: recommend repeat CTC in 5 y
Uncertain benign: recommend repeat CTC in ≤3 y

C3 = Polyp, Possibly Advanced Adenoma

Recommendation: Colonoscopy
Communicate to referring physician as per accepted guidelines for communication, such as American College of Radiology Practice Parameter for Communication of Diagnostic Imaging Findings. Subject to local practice, endoscopic biopsy may be indicated.

C4 = Likely Malignant Colonic Mass

Recommendation: Surgical and/or oncologic consultation.
Communicate to referring physician as per accepted guidelines for communication, such as American College of Radiology Practice Parameter for Communication of Diagnostic Imaging Findings. Subject to local practice, endoscopic biopsy may be indicated.

Extra-colonic findings

Which of the following applies to the current exam?

E0

Incidence rate of 3%

E1/E2

Incidence rate of 86-88%
No additional workup is indicated

E3

Incidence rate of 4-16%
Further workup may be warranted

E4

Incidence rate of 2-8%
Further workup needed
The scoring of extracolonic findings per C-RADS is very straightforward. Please refer to the following table:

E0 = Limited examCompromised by artifact; evaluation of extracolonic soft tissues is severely limited.No recommendations.
E1 = Normal exam or anatomic variantNo extracolonic abnormalities visible.
Anatomic Variant: eg, retroaortic left renal vein
No recommendations.
E2 = Clinically unimportant findingExamples:
a. Liver, Kidney: simple cysts
b. Gallbladder: cholelithiasis without cholecystitis
c. Vertebra: hemangioma
No work-up indicated.
E3 = Likely unimportant finding or incompletely characterizedExamples:
a. Kidney: minimally complex or homogeneously hyperattenuating cyst
Subject to local practice and patient preference,
work-up may be indicated.
E4 = Potentially important findingExamples:

a. Kidney: solid renal mass
b. Lymphadenopathy
c. Vasculature: aortic aneurysm
d. Lung: non-uniformly calcified parenchymal nodule ≥1 cm

Communicate to referring physician as per accepted practice guidelines.

Related Calculators:

More about the C‑RADS® 2023 Calculator:

The CT Colonography Reporting and Data System (C‑RADS®), endorsed by the American College of Radiology, is a standardized lexicon for classifying findings on CT colonography (CTC). Since its inception in 2005, C‑RADS has become a cornerstone for consistent reporting of both colonic and extracolonic discoveries. The 2023 update streamlines the system by introducing nuanced categories, enhancing the clarity and practical utility of CTC interpretation :contentReference[oaicite:1]{index=1}.

Key Updates in 2023
  • New C2b Subcategory: Differentiates mass-like diverticular strictures that mimic polyps but are typically benign, reducing unnecessary colonoscopies :contentReference[oaicite:2]{index=2}.
  • Extracolonic Simplification: Merges E1 and E2 into a single E1/E2 category, reflecting that neither warrants additional follow-up :contentReference[oaicite:3]{index=3}.
C‑RADS® Categories and Corresponding Actions
  • C0: Incomplete or inadequate CTC—repeat recommended.
  • C1: Normal colon or benign findings—return to routine screening.
  • C2a: Indeterminate polyps (6–9 mm)—watchful CTC or colonoscopy follow-up.
  • C2b: Likely benign mass-like strictures—targeted follow-up vs immediate colonoscopy.
  • C3: Suggestive of advanced adenoma—recommend diagnostic colonoscopy.
  • C4: Highly suspicious mass—urgent colonoscopy and oncology referral.
Extracolonic Findings (E‑Categories)

Findings outside the colon are classified as E1/E2 when benign or clinically unimportant, requiring no follow-up. More concerning abnormalities are categorized as E3 (likely significant) or E4 (potentially serious), which may necessitate further imaging or clinical action.

Clinical and Operational Advantages
  • Enhanced Consistency: ACR-developed framework improves diagnostic clarity and reduces reporting variation :contentReference[oaicite:4]{index=4}.
  • Optimized Workflow: Categorization guides targeted follow-up, minimizing unnecessary invasive procedures.
  • Patient-Centered Care: Stratifies risk to avoid both over-treatment and underdiagnosis.
  • Data-Driven Quality: Uniform terminology supports research, audit, and quality improvement initiatives :contentReference[oaicite:5]{index=5}.
Using the C‑RADS 2023 Calculator

The C‑RADS 2023 calculator automates categorization based on polyp size, morphology, and extracolonic findings. It provides clear, reproducible outputs that can be integrated into radiology reports and EMR systems. This leads to:

  • Standardized interpretation in line with ACR‐endorsed terminology
  • Automated follow-up recommendations (e.g. C2a → repeat CTC in 3 years)
  • Support for multidisciplinary collaboration and patient discussions
Conclusion

The C‑RADS® 2023 update refines classification, introduces meaningful subcategories, and simplifies reporting to improve clinical value. By leveraging this tool, radiologists and clinicians can deliver evidence-based, consistent, and patient-centered colorectal screening care.

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