LI-RADS CT/MRI Reporting: Observation Worksheet and Report Examples

LI-RADS CT/MRI reporting: scope and quick framework

This guide uses the ACR LI-RADS CT/MRI diagnostic algorithm, version 2018. As of the date of this article, the ACR lists v2018 for CT/MRI diagnosis. The ACR lists separate v2024 CT/MRI treatment-response cores for nonradiation and radiation-based therapies. Name the pathway and version in local documentation when it matters; do not apply a treatment-response category to an untreated observation.

A useful LI-RADS report connects three things: the patient’s eligibility, the technical adequacy of the multiphase examination, and the imaging features that support each observation’s category. A category is a probability-based imaging assessment in the population for which the algorithm was designed; it is not a histologic result.

Eligibility and examination checklist

Before assigning categories, confirm that:

• The patient is an adult in an intended high-risk group: cirrhosis, chronic hepatitis B infection, or current or prior hepatocellular carcinoma (HCC).
• The cirrhosis is not due to congenital hepatic fibrosis or a specified vascular disorder, populations excluded from the v2018 diagnostic algorithm.
• The examination is a multiphase CT or contrast-enhanced MRI suitable for liver lesion characterization. A single portal-venous phase CT or noncontrast MRI does not provide the required feature set.
• The relevant phases and liver coverage are adequate. For CT and MRI with an extracellular agent, review the arterial, portal venous, and delayed phases; for MRI with a hepatobiliary agent, review the phases specified by the protocol, including the transitional and hepatobiliary phases.
• Image degradation, omitted phases, or limited coverage are recorded. Use LR-NC only when an eligible observation cannot be categorized because of image omission or degradation.
• Prior examinations are available when possible, with modality, date, and the observation’s prior size recorded.
• Treated observations are separated from new or untreated observations and assessed with the appropriate treatment-response pathway.

Do not apply diagnostic LI-RADS to an incidental liver lesion in a patient outside the eligible population. Do not assign a LI-RADS category to a path-proven malignancy or a path-proven benign lesion of non-hepatocellular origin. If the clinical risk group or protocol is uncertain, state the limitation and use the appropriate non-LI-RADS assessment.

Observation worksheet

Complete one row for each untreated observation. Record the features that were actually evaluated; avoid inferring an absent feature from a phase that was not acquired or was nondiagnostic.

For each observation, describe its location and maximum diameter, then state the major features that drive the category. Major features include nonrim arterial phase hyperenhancement (APHE), nonperipheral washout, enhancing capsule, and threshold growth. Ancillary features may improve confidence or adjust a category within the limits of the algorithm; they cannot upgrade an observation to LR-5. If a major feature is uncertain, apply the v2018 tie-breaking rule rather than calling it present.

Report tumor in vein separately when criteria are met. If an observation is probably or definitely malignant but not specific for HCC, LR-M communicates that distinction. Do not equate LR-M with a particular tumor type.

Reusable diagnostic report framework

Examination: Multiphase CT of the liver / MRI of the liver without and with intravenous contrast [agent type if relevant].

Indication: [Clinical indication and HCC risk factor establishing LI-RADS eligibility.]

Comparison: [Date and modality, or none available.]

Technique and limitations: [Phases/sequences obtained; image quality; relevant limitations.]

Findings:
Liver: [Morphology, background parenchyma, and other clinically relevant findings.]

Observation #1: Segment [ ], [ ] mm (series/image). [Nonrim APHE: present/absent. Nonperipheral washout: present/absent/not assessable. Enhancing capsule: present/absent/not assessable. Threshold growth: present/absent/not assessable, with comparison interval.] [Ancillary features, if used.] Category: LR-[ ] (LI-RADS CT/MRI v2018).

[Repeat the observation block for each untreated observation.]

Tumor in vein: [Absent / present with vessel and extent / not assessable.]

Other staging-relevant findings: [Portal/hepatic venous findings, lymph nodes, extrahepatic disease, ascites, and other relevant findings within the examination scope.]

Impression:
1. [Observation, segment, size, category, and concise supporting features.]
2. [Additional observation or tumor-in-vein finding.]
3. [Other important finding or stated limitation.]

The framework is not a substitute for confirming eligibility, reviewing every acquired phase, and applying the current local pathway.

Worked example: untreated observation categorized LR-5

Fictional teaching case. A 67-year-old adult with chronic hepatitis B undergoes multiphase liver MRI. The study uses an extracellular contrast agent and is diagnostic. The example assumes that the clinical history confirms LI-RADS eligibility.

Examination: MRI of the liver without and with intravenous extracellular contrast.

Indication: Chronic hepatitis B; characterization of a liver observation.

Comparison: Multiphase CT dated [date], when the observation measured 9 mm.

Technique: Multiplanar, multisequence MRI with precontrast imaging and postcontrast arterial, portal venous, and delayed phases. Diagnostic image quality.

Findings:
The liver has mildly nodular contour. Observation #1 in segment VIII measures 12 mm. It demonstrates nonrim arterial phase hyperenhancement and nonperipheral washout on the portal venous phase. No enhancing capsule is seen. The size change from 9 mm to 12 mm does not meet threshold growth. No tumor in vein is identified. The portal and hepatic veins are patent. No ascites or upper abdominal lymphadenopathy is identified.

Impression:
1. Segment VIII observation measuring 12 mm with nonrim arterial phase hyperenhancement and nonperipheral washout: LR-5 by LI-RADS CT/MRI v2018.
2. No tumor in vein.

In the v2018 diagnostic table, a 10–19 mm observation with nonrim APHE and nonperipheral washout meets LR-5 criteria. The comparison is included, but the example does not call a 3 mm change threshold growth. In an eligible patient, LR-5 is the imaging category for a lesion considered definitely HCC under the algorithm; it does not mean pathology was obtained.

Selected variants

Limited or incomplete diagnostic examination

Technique and limitations: The arterial phase is nondiagnostic because of severe motion. Observation #1 in segment [ ] measures [ ] mm. The required major features cannot be assessed reliably. Category: LR-NC due to image degradation.
Impression: Observation #1 is not categorizable on this examination (LR-NC). Repeat or alternative diagnostic imaging may be considered in the clinical context.

Use LR-NC only when the examination is inadequate to categorize an observation; do not use it as a synonym for uncertainty between two categories.

Previously treated observation

Treated observation #1 in segment [ ], treatment [type/date]: [LR-TR category] by the applicable ACR CT/MRI treatment-response pathway, version [ ]. Viable tumor component measures [ ] mm, if applicable. [Describe enhancement and comparison.]

For treatment response, identify whether the observation received radiation-based or nonradiation locoregional therapy and use the corresponding ACR CT/MRI TRA v2024 core. Untreated observations elsewhere in the liver continue to use the diagnostic algorithm. Do not label a treated lesion LR-5 simply because its pretreatment category was LR-5.

Common wording pitfalls and scope limits

• Skipping eligibility: “LR-5” does not carry the same validated meaning in every patient with a liver mass. Record the risk factor that makes the pathway applicable.
• Treating a single-phase study as a full diagnostic examination: If the needed enhancement phases are absent or nondiagnostic, state the limitation and avoid unsupported categorization.
• Listing a category without its basis: Include segment, size, and the major feature combination. This makes the conclusion easier to audit.
• Promoting ancillary features to major features: Ancillary features do not independently support LR-5.
• Using “washout” without the required phase or definition: Describe the observed phase and apply the v2018 lexicon.
• Confusing diagnosis and response: LR-1 through LR-5, LR-M, LR-TIV, and LR-NC are diagnostic categories. LR-TR categories belong to treated observations and a treatment-specific response algorithm.
• Overstating extrahepatic coverage: Name the structures evaluated and do not imply a dedicated staging examination if only a liver protocol was acquired.

References

• American College of Radiology. LI-RADS CT/MRI v2018 Core. PDF (opens in a new tab)
• American College of Radiology. LI-RADS resources and current releases. ACR LI-RADS (opens in a new tab)
• American College of Radiology. LI-RADS CT/MRI Nonradiation Treatment Response Assessment v2024 Core. PDF (opens in a new tab)
• American College of Radiology. LI-RADS CT/MRI Radiation Treatment Response Assessment v2024 Core. PDF (opens in a new tab)

Educational note: This article is a reporting aid. Interpret each examination in context and confirm the pathway, protocol, and category against current ACR guidance and local practice.