Table 1.

Kidney injury scale – 2018 revision

AAST grade	AIS severity	Imaging criteria (CT findings)	Operative goals	Pathological criteria
I	2	– Subcapsular hematoma and/or parenchymal contusion without laceration	– Non-expanding subcapsular hematoma – Parenchymal contusion without laceration	– Subcapsular hematoma or parenchymal contusion without parenchymal laceration
II	2	– Peri-renal hematoma confined to Gerota fascia – Renal parenchymal laceration ≤1 cm depth without urinary extravasation	– Non- expanding peri-renal hematoma confined to Gerota fascia – Renal parenchymal laceration ≤1 cm depth without urinary extravasation	– Peri-renal hematoma confined to Gerota fascia – Renal parenchymal laceration ≤1 cm depth without urinary extravasation
III	3	– Renal parenchymal laceration >1 cm depth without collecting system rupture or without urinary extravasation – Any injury in the presence of a kidney vascular injury or active bleeding contained within Gerota fascia	– Renal parenchymal laceration >1 cm depth without collecting system rupture or without urinary extravasation	– Renal parenchymal laceration >1 cm depth without collecting system rupture or without urinary extravasation
IV	4	– Parenchymal laceration extending into urinary collecting system with urinary extravasation – Renal pelvis laceration and/or complete ureteropelvic disruption – Segmental renal vein or artery injury – Active bleeding beyond Gerota fascia into the retroperitoneum or peritoneum – Segment or complete kidney infarction(s) due to vessel thrombosis without active bleeding	– Parenchymal laceration extending into urinary collecting system with urinary extravasation – Renal pelvis laceration and/or complete ureteropelvic disruption – Segmental renal vein or artery injury – Segment or complete kidney infarction(s) due to vessel thrombosis without active bleeding	– Parenchymal laceration extending into urinary collecting system – Renal pelvis laceration and/or complete ureteropelvic disruption – Segmental renal vein or artery injury – Segment or complete kidney infarction(s) due to vessel thrombosis without active bleeding
V	5	– Main renal artery or vein laceration or avulsion of hilum – Devascularized kidney with active bleeding – Shattered kidney with loss of identifiable parenchymal renal anatomy	– Main renal artery or vein laceration or avulsion of hilum – Devascularized kidney with active bleeding – Shattered kidney with loss of identifiable parenchymal renal anatomy	– Main renal artery or vein laceration or avulsion of hilum – Devascularized kidney – Shattered kidney with loss of identifiable parenchymal renal anatomy

Vascular injury is defined as a pseudoaneurysm or arteriovenous fistula and appears as a focal collection of vascular contrast that decreases in attenuation with delayed imaging. Active bleeding from a vascular injury presents as vascular contrast, focal or diffuse, that increases in size or attenuation in delayed phase. Vascular thrombosis can lead to organ infarction. Grade based on highest grade assessment made on imaging, at operation, or on pathologic specimen. More than one grade of kidney injury may be present and should be classified by the higher grade of injury. Advance one grade for bilateral injuries up to Grade III. AAST: American Association for the Surgery of Trauma; AIS: abbreviated injury scale; CT: computed tomography.