What Does LI-RADS 4 Mean?

LI-RADS is the Liver Imaging Reporting and Data System, a scoring scheme from the American College of Radiology for liver CT and MRI. Its diagnostic categories run LR-1 through LR-5, and each one carries a fixed meaning. LR-5 means definitely hepatocellular carcinoma, the main type of primary liver cancer, usually written HCC. LR-4 means probably HCC.

That gap is not a technicality. LR-5 sends a person to staging and treatment without a biopsy. LR-4 does not. It is a call for more information, and the report is telling you that the scan came close to the HCC pattern but did not complete it.

LI-RADS is applied only to adults 18 and older in one of three groups: people with cirrhosis from a cause other than a blood vessel problem, people with chronic hepatitis B infection even without cirrhosis, and people with current or previously treated HCC.

If none of those describe you, an LR category should not have been assigned, and the finding needs a different framework.

LI-RADS scores five major features. Size is one. Nonrim arterial phase hyperenhancement means the lesion brightens more than the liver around it during the arterial contrast phase, filling in rather than forming a ring. Nonperipheral washout means it turns darker than the liver around it on the later phases. An enhancing capsule is a bright rim on those later images. The fifth is threshold growth.

Threshold growth has a hard definition. It means a size increase of 50% or more in 6 months or less. Anything slower is subthreshold growth, which since the 2018 revision is only an ancillary feature.

LR-4 collects observations carrying some of that pattern but not the specific combination LI-RADS demands for LR-5. One documented example: an observation 20 mm or larger with no nonrim arterial phase hyperenhancement but with an enhancing capsule is categorized LR-4.

For contrast, an observation of 10 to 19 mm with nonrim arterial hyperenhancement and nothing else is LR-3, one step below. LR-5 typically requires that arterial brightening plus washout or threshold growth.

An analysis pooling 7,500 observations put the positive predictive value of LR-4 at 80.82%. The 95% confidence interval ran from 71.04% to 87.86%. In plain terms, roughly four out of five LR-4 observations turn out to be HCC.

A separate pooled analysis of 49 studies broke it down by scan type. HCC was found in 76% of LR-4 observations on CT, 64% on MRI with extracellular contrast agents, and 77% on MRI with gadoxetate. The differences between those methods were not statistically significant.

Not every LR-4 carries the same weight. That 20 mm or larger observation with a capsule but no arterial hyperenhancement had a positive predictive value of only 50.81%. Its confidence interval ran from 28.92% to 72.39%. That is a coin flip, and it sits inside the same category as observations far more likely to be cancer. If the report is LR-4, the specific features behind it are worth reading, not just the number.

Radiologists also record ancillary features, smaller signals that can nudge a category. LI-RADS has one firm rule about them: ancillary features cannot be used to upgrade an observation from LR-4 to LR-5.

So a radiologist may look at a lesion, believe it is cancer, list several supporting signs, and still write LR-4. The rules do not allow the jump. The 2018 revision also dropped the old LR-5us and LR-5g qualifiers. Those had let ultrasound history and growth feed the top category in ways that varied between readers.

LI-RADS does not prescribe a single next step here. The recommended management is an individualized workup with multidisciplinary input, and it can go three ways: biopsy, presumptive treatment, or continued imaging follow-up.

Compare that with the neighbors. LR-3 gets repeat or alternative imaging in 3 to 6 months. LR-5 goes to staging and treatment planning. LR-4 is where a tumor board earns its keep. The same report can lead to a needle or to a repeat MRI. It depends on lesion size, liver function, and what treatment is even possible.

Two practical questions decide a lot. Would a biopsy change what happens next, or would the plan be the same either way. And is the person a transplant candidate, since that changes the value of a firm diagnosis.

These get confused because both sound worrying.

LR-M means probably or definitely malignant but not specific for HCC. In the 49-study analysis, LR-M observations were HCC only 20% to 35% of the time depending on scan type, but 93% to 100% were malignant in some form. Many turn out to be intrahepatic cholangiocarcinoma, a bile duct cancer treated very differently from HCC.

LR-TIV means tumor in vein, and 99% to 100% of those observations are malignant.

So LR-M is not a milder LR-4. It is a different question about which cancer, and it usually does call for biopsy.

For liver transplant priority in the United States, the Organ Procurement and Transplantation Network accepts an LI-RADS 5 report as a Class 5 lesion when scoring HCC exceptions, a policy alignment effective July 1, 2025. LR-4 is not on that list.

That is a concrete reason a transplant center may push for a definite answer rather than watching. If you are being evaluated for transplant, ask directly whether the current LR-4 affects your listing or your exception score, and what would resolve it.

Three outcomes are realistic. A repeat scan in a few months either settles the finding or upgrades it. A biopsy names the tissue. Or treatment goes ahead on the imaging plus everything else known about your liver.

None of those is a failure of the first scan. LI-RADS was built to keep uncertain findings labeled as uncertain instead of quietly rounding them up or down. Ask which features produced the LR-4. Ask what the lesion measures in millimeters. Ask when the next scan is set, and whether a liver tumor board has seen the images.

• Radiology (RSNA) — Diagnostic Performance of CT/MRI LI-RADS v2018 Major Feature Combinations
• Radiology (RSNA) — Percentages of Hepatocellular Carcinoma in LI-RADS Categories with CT and MRI
• PubMed Central (Radiology) — LI-RADS Version 2018: Imaging of Hepatocellular Carcinoma
• National Cancer Institute — Primary Liver Cancer Treatment (PDQ) Health Professional Version
• OPTN/HRSA — Alignment of National Liver Review Board Guidance and LI-RADS
• American College of Radiology — Liver Imaging Reporting and Data System (LI-RADS)