LI-RADS (overview)

LI-RADS (Liver Imaging Reporting and Data System) is both a set of standardizedstandardised terminology and a classification system for imaging findings in liver lesions. The LI-RADS score for a liver lesion is an indication of its relative risk forhepatocellular carcinoma (HCC). The classification system is meant to be used in livers which have risk factors for HCC (e.g. cirrhotic livers).

The classification is meant to help decrease the variability in interpretation of liver lesions in at-risk patients. StandardizationStandardisation also helps interpret therapeutic performance. The scoring system also potentially helps non-hepatologists interpret the potential supsiciousness of of liver lesions in their patients.

StandardizedStandardised terminology

Major criteria

• hepatic phase enhancement
  • hyperenhancement: enhancement in the arterial phase is definitely greater than that of background liver
  • if unsure, classify as isoenhancing
• "washout"
  • a visual assessment of relative hypointensity of the lesion compared with background liver on the portal venous and delayed phases
• capsule/pseudocapsule
  • peripheral rim of smooth hyperenhancement seen on the portal venous or delayed phases
• threshold growth
  • diameter increase of a mass by a minimum of 5 mm
  • also
    • if prior exam ≤6 months, diameter ≥50% increase
    • if prior exam >6 months, diameter ≥100% increase
  • a new 10 mm lesion represents threshold growth, regardless of time interval
  • threshold growth only applies to masses
  • threshold growth should be compared on similar sequences between studies

Ancillary features

• favoring HCC
  • mild-moderate T2 hyperintensity
  • restricted diffusion
  • corona enhancement (rim of peri-lesional enhancement)
  • mosaic architecture
  • nodule-in-nodule architecture
  • intralesional fat
  • lesional iron sparing
  • lesional fat sparing
  • blood products
  • diameter increase (less than threshold growth)
• favoring benignity
  • homogeneous marked T2 hyperintensity
  • homogeneous marked T2 or T2* hypointensity
  • undistorted vessels
  • parallels blood pool enhancement
  • diameter reduction
  • diameter stability >2 years

Classification system

Major criteria imaging findings often leads directly to the assignment of a LI-RADS score.  If assignment is unclear, ancillary findings may be useful as a "tie-breaker."

The LI-RADS score ranges from L1 (favor benignity benignity) to L5 (favor malignancy).

LR1 (100% benign)

• imaging features diagnostic of a benign entity:
  • cyst
  • haemangioma
  • vascular anomaly
  • perfusion alteration
  • hypertrophic pseudomass
  • confluent hepatic fibrosis
  • focal scar
• definite disappearance at follow up in the absence of treatment is also definitional of LR1

LR2 (probably benign)

• entities are similar to LR1, but the appearance is highly suggestive of the entity instead instead of 100% diagnostically certain
  • ​atypical appearance of benign entities may be categorizedcategorised as LR2
  • LR2 cirrhosis-associated nodule is also included

LR3 (intermediate probability for HCC)

• not a definitely benign entity, but not definitely HCC
• includes entities that demonstrate
  • not a definite mass
  • mass withhepatic arterial phase iso- or hypoenhancement
    • <20 mm withno more than oneof the following:
      • "washout"
      • capsule
      • threshold growth
    • ≥20 mm with no "washout," capsule, or threshold growth
  • mass withhepatic arterial phase hyperenhancement
    • <20 mm with no "washout," capsule, or threshold growth

LR4 (probably HCC)

• LR4A (<20 mm mass)
  • mass withhepatic arterial phase iso- or hypoenhancement
    • ​two or more of the following
      • "washout"
      • capsule
      • threshold growth
  • mass withhepatic arterial phase hyperenhancement
    • ​<10 mm withone or more of the following
      • "washout"
      • capsule
      • threshold growth
    • 10-19 mm withonly one of the following
      • "washout"
        • if just washoutand was seen as a discrete nodule on a prior screening ultrasound, then "LR-5us")
      • capsule
      • threshold growth 
        • (if just threshold growth, then "LR-5g" (equivalent of OPTN 5A-g))
• LR4B (>20 mm mass)
  • mass withhepatic arterial phase iso- or hypoenhancement
    • ​one or more of the following
      • "washout"
      • capsule
      • threshold growth
  • mass withhepatic arterial phase hyperenhancement
    • noneof the following
      • "washout"
      • capsule
      • threshold growth

LR5 (100% definite HCC)

• LR5A (10-19 mm mass)
  • mass withhepatic arterial phase hyperenhancement
    • ​two or more of the following
      • "washout"
      • capsule
      • threshold growth
• LR5B (>20 mm mass)
  • mass withhepatic arterial phase hyperenhancement
    • ​one or more of the following
      • "washout"
      • capsule
      • threshold growth

There is a special categoryLR5Vfor HCC that is invading the portal vein. This is reported since it is a contraindication to liver transplantation.

There is also a special category forLR5 Treated, in the case of lesions that have received loco-regional therapy (e.g. TACE or thermal ablation). This category is being further developed.

Suggested management

• LR1: Continued routine surveillance
• LR2: Continued routine surveillance
• LR3: Variable follow up, depending on size, stability, and clinical presentation
• LR4: Close follow up, additional imaging, biopsy, or treatment
• LR5: Treatment without biopsy, radiologic T-staging

Practical points

• ancillary features cannot upgrade a lesion to LR5
• if there are no LR4 or LR5 lesions, then LR3 should be reported, otherwise reporting of LR3 lesions is at the radiologist's discretion (they should be reported if previously LR4 or LR5)
• late arterial phase is preferred for evaluation of arterial hyperenhancement
• for masses with nodule-in-nodule appearance, measure the entire mass

See also

• OPTN classification