AAST liver injury scale

Last revised by Rohit Sharma on 3 Apr 2024

The AAST (American Association for the Surgery of Trauma) liver injury scale, revised in 2018, is the most widely used liver injury grading system 3.

The 2018 update incorporates "vascular injury" (i.e. pseudoaneurysm, arteriovenous fistula) into the imaging criteria for visceral injury 3.


  • grade I

    • hematoma: subcapsular, <10% surface area

    • laceration: capsular tear, <1 cm parenchymal depth

  • grade II

    • hematoma: subcapsular, 10-50% surface area

    • hematoma: intraparenchymal <10 cm diameter

    • laceration: capsular tear 1-3 cm parenchymal depth, <10 cm length

  • grade III

    • hematoma: subcapsular, >50% surface area; ruptured subcapsular or parenchymal hematoma

    • hematoma: intraparenchymal >10 cm

    • laceration: capsular tear >3 cm parenchymal depth

    • vascular injury with active bleeding contained within liver parenchyma

  • grade IV

    • laceration: parenchymal disruption involving 25-75% of a hepatic lobe or involves 1-3 Couinaud segments 

    • vascular injury with active bleeding breaching the liver parenchyma into the peritoneum

  • grade V

    • laceration: parenchymal disruption involving >75% of hepatic lobe

    • vascular: juxtahepatic venous injuries (retrohepatic vena cava / central major hepatic veins)

Additional points

  • advance one grade for multiple injuries up to grade III

  • for each grade, the worst feature is chosen, either hematoma or laceration (no need for both/all to coexist)

  • "vascular injury" (i.e. pseudoaneurysm or AV fistula): appears as a focal collection of vascular contrast which decreases in attenuation on delayed images

  • "active bleeding": focal or diffuse collection of vascular contrast which increases in size or attenuation on a delayed phase

Imaging technique

The AAST guidelines recommend dual arterial/portal venous phase imaging to evaluate a vascular injury of the liver, spleen, or kidney 3.

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