Definition:
Macroscopically evident benign process of scarring in the liver parenchyma.
LI-RADS Categorization:
- Observations thought to definitely represent confluent fibrosis should be categorized LR-1.
- Observations thought to probably represent confluent fibrosis should be categorized LR-2.
- Observations that are indeterminate for confluent fibrosis versus HCC should be categorized LR-3 or LR-4.
Imaging Manifestations:
- Confluent fibrosis typically has the following features:
- Band-like, wedge-like, or geographic shape
- Straight or concave borders
- Radiates from portal hilus to contact liver surface
- Peripherally located
- Often involves central segments (4, 5, 8)
- Associated with parenchymal volume loss and liver surface retraction; the volume loss often progresses on follow-up studies
- Unenhanced CT
- Unenhanced MRI
- T1 hypointense
- T2 hyperintense
- DW hyperintense (due at least in part to T2 shine-through)
- Hypo- or isoenhancing in the arterial phase
- Increasing enhancement in portal venous and delayed phases (if extra-cellular contrast agent is administered)
- Multiplanar images may help to depict the characteristic morphology: band-like or wedge-like shape; straight or concave borders.
Pitfalls, Challenges, Differential Diagnosis:
- While confluent fibrosis typically is arterial phase hypo- or isoenhancing, it may be arterial phase hyperenhancing. Characteristic morphology and location usually permit correct interpretation and appropriate LI-RADS categorization as, depending on level of confidence, LR-1 or LR-2.
- Confluent fibrosis may overlap in imaging appearance with HCC.
- Features that favor confluent fibrosis:
- Features that favor HCC:
- Confluent fibrosis may overlap in imaging appearance with intrahepatic cholangiocarcinoma (ICC).
- Features that favor confluent fibrosis:
- Features that favor ICC
Other Comments:
- Confluent fibrosis is more common in PSC, secondary biliary cirrhosis, and alcoholic liver disease than in viral liver disease.