The AAST (American Association for the Surgery of Trauma) liver injury scale, most recently 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.

Classification

·       grade I

o   haematoma: subcapsular, <10% surface area

o   laceration: capsular tear, <1 cm  parenchymal depth

·       grade II

o   haematoma: subcapsular, 10-50% surface area

o   haematoma: intraparenchymal <10 cm diameter

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

·       grade III

o   haematoma: subcapsular, >50% surface area of ruptured subcapsular or parenchymal haematoma

o   haematoma: intraparenchymal >10 cm

o   laceration: capsular tear >3 cm parenchymal depth

o   vascular injury with active bleeding contained within liver parenchyma

·       grade IV

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

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

·       grade V

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

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

Additional points

·       advance one grade for multiple injuries up to grade III

·       “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