Quick reference · AAST 2018 revision

AAST Organ Injury Grading — Spleen · Liver · Kidney

CT imaging criteria and an original schematic for every grade

Any single criterion assigns the grade. Grade by the highest finding on imaging, at operation or on pathology, and use the higher grade when more than one injury grade is present. Where a vascular injury or active bleeding lands sets the grade differently for each organ.

AAST 2018 · CT imaging criteria

Spleen injury grades

Any single criterion assigns the grade.

Vascular injury or active bleeding: where it lands sets the grade (inside the splenic capsule versus beyond it into the peritoneum)

Confined within the splenic capsule

Grade IV

Beyond the spleen into the peritoneum

Grade V

Drawing key

Parenchyma and capsule
Artery
Vein
Subcapsular hematoma
Intraparenchymal hematoma
Laceration, with depth bracket
Vascular injury (pseudoaneurysm or AV fistula)
Active bleeding, contained within the capsule
Active bleeding, extending into the peritoneum
Devascularized or infarcted tissue

Labels in the drawings: PSA = pseudoaneurysm. Depth brackets measure a laceration from the capsule inward.

Grade I

AIS 2

Subcapsular hematoma < 10% surface area
Parenchymal laceration < 1 cm depth
Capsular tear

Grade II

AIS 2

Subcapsular hematoma 10–50% surface area
Intraparenchymal hematoma < 5 cm
Parenchymal laceration 1–3 cm

Grade III

AIS 3

Subcapsular hematoma > 50% surface area
Ruptured subcapsular or intraparenchymal hematoma ≥ 5 cm
Parenchymal laceration > 3 cm depth

Grade IV

AIS 4

Any injury with splenic vascular injury or active bleeding confined within the splenic capsule
Parenchymal laceration involving segmental or hilar vessels producing > 25% devascularization

Grade V

AIS 5

Any injury with splenic vascular injury and active bleeding extending beyond the spleen into the peritoneum
Shattered spleen

At operation or on pathology, grade V also includes hilar vascular injury that devascularizes the spleen.

AAST 2018 · CT imaging criteria

Liver injury grades

Any single criterion assigns the grade.

Vascular injury or active bleeding: where it lands sets the grade (inside the liver parenchyma versus beyond it into the peritoneum)

Contained within the liver parenchyma

Grade III

Beyond the liver parenchyma into the peritoneum

Grade IV

Drawing key

Parenchyma and capsule
IVC and hepatic veins (behind the liver)
Subcapsular hematoma
Intraparenchymal hematoma
Laceration, with depth bracket
Vascular injury (pseudoaneurysm or AV fistula)
Active bleeding, contained within the parenchyma
Active bleeding, extending into the peritoneum
Parenchymal disruption

Labels in the drawings: PSA = pseudoaneurysm. Depth brackets measure a laceration from the capsule inward.

Grade I

AIS 2

Subcapsular hematoma < 10% surface area
Parenchymal laceration < 1 cm in depth

Grade II

AIS 2

Subcapsular hematoma 10–50% surface area
Intraparenchymal hematoma < 10 cm in diameter
Laceration 1–3 cm in depth and ≤ 10 cm in length

Grade III

AIS 3

Subcapsular hematoma > 50% surface area
Ruptured subcapsular or parenchymal hematoma
Intraparenchymal hematoma > 10 cm
Laceration > 3 cm in depth
Any injury with liver vascular injury or active bleeding contained within the liver parenchyma

Grade IV

AIS 4

Parenchymal disruption involving 25–75% of a hepatic lobe
Active bleeding extending beyond the liver parenchyma into the peritoneum

Grade V

AIS 5

Parenchymal disruption > 75% of a hepatic lobe
Juxtahepatic venous injury (retrohepatic vena cava and central major hepatic veins)

AAST 2018 · CT imaging criteria

Kidney injury grades

Any single criterion assigns the grade.

Version note: AAST published a 2025 kidney revision (Keihani et al., J Trauma Acute Care Surg 2025;98(3):448-451) that changes several definitions, including moving collecting-system injury to grade III. This reference and the site's renal algorithm use the 2018 scale.

Vascular injury or active bleeding: where it lands sets the grade (inside the Gerota fascia versus beyond it into the retroperitoneum or peritoneum)

Contained within Gerota fascia

Grade III

Beyond Gerota fascia into the retroperitoneum or peritoneum

Grade IV

Drawing key

Parenchyma and capsule
Renal pelvis, calyces and ureter
Artery
Vein
Gerota fascia
Subcapsular hematoma
Contusion
Perirenal hematoma
Laceration, with depth bracket
Vascular injury (pseudoaneurysm or AV fistula)
Active bleeding, contained within Gerota fascia
Active bleeding, extending beyond Gerota fascia
Urinary extravasation

Labels in the drawings: PSA = pseudoaneurysm. Depth brackets measure a laceration from the capsule inward.

Grade I

AIS 2

Subcapsular hematoma and/or parenchymal contusion without laceration

Grade II

AIS 2

Perirenal hematoma confined to Gerota fascia
Parenchymal laceration ≤ 1 cm depth without urinary extravasation

Grade III

AIS 3

Parenchymal laceration > 1 cm depth without collecting system rupture or urinary extravasation
Any injury with kidney vascular injury or active bleeding contained within Gerota fascia

Grade IV

AIS 4

Laceration extending into the collecting system with urinary extravasation
Renal pelvis laceration and/or complete ureteropelvic disruption
Segmental renal artery or vein injury
Active bleeding beyond Gerota fascia into the retroperitoneum or peritoneum
Segmental or complete kidney infarction from vessel thrombosis without active bleeding

Grade V

AIS 5

Main renal artery or vein laceration or avulsion of the hilum
Devascularized kidney with active bleeding
Shattered kidney with loss of identifiable parenchymal anatomy

Definitions and grading rules

Vascular injury: Pseudoaneurysm or arteriovenous fistula: a focal collection of vascular contrast that decreases in attenuation on delayed images.
Active bleeding: Vascular contrast, focal or diffuse, that increases in size or attenuation on delayed images.
Vascular thrombosis: Can lead to organ infarction.

Grade by the highest finding on imaging, at operation or on pathology. When more than one grade of injury is present, classify by the higher grade.
Spleen and liver: advance one grade for multiple injuries, up to grade III. Kidney: advance one grade for bilateral injuries, up to grade III.
Dual-phase CT (arterial + portal venous) is recommended to detect vascular injury.

Where contained vascular injury or bleeding lands differs by organ

Organ	Contained	Beyond the boundary
Spleen	Confined within the splenic capsule = Grade IV	Beyond the spleen into the peritoneum = Grade V
Liver	Contained within the liver parenchyma = Grade III	Beyond the liver parenchyma into the peritoneum = Grade IV
Kidney	Contained within Gerota fascia = Grade III	Beyond Gerota fascia into the retroperitoneum or peritoneum = Grade IV

Definitions and grading rules

Vascular injury

Pseudoaneurysm or arteriovenous fistula: a focal collection of vascular contrast that decreases in attenuation on delayed images.

Active bleeding

Vascular contrast, focal or diffuse, that increases in size or attenuation on delayed images.

Vascular thrombosis

Can lead to organ infarction.

Grade by the highest finding on imaging, at operation or on pathology. When more than one grade of injury is present, classify by the higher grade.

Spleen and liver: advance one grade for multiple injuries, up to grade III. Kidney: advance one grade for bilateral injuries, up to grade III.

Dual-phase CT (arterial + portal venous) is recommended to detect vascular injury.

Where contained vascular injury or bleeding lands differs by organ

Organ	Contained	Beyond the boundary
Spleen	Confined within the splenic capsule = Grade IV	Beyond the spleen into the peritoneum = Grade V
Liver	Contained within the liver parenchyma = Grade III	Beyond the liver parenchyma into the peritoneum = Grade IV
Kidney	Contained within Gerota fascia = Grade III	Beyond Gerota fascia into the retroperitoneum or peritoneum = Grade IV