Grade I
Contusion-Microscopic or gross hematuria, urologic studies normal
Hematoma-Subcapsular, nonexpanding without parenchymal laceration
Grade II
Hematoma -Nonexpanding perirenal hematoma confirmed to renal retroperitoneum
Laceration < 1cm, without extension into the renal pelvis or collecting system and with no evidence of urine extravasation
Grade III
Laceration > 1cm, without extension into the renal pelvis or collecting system and with no evidence of urine extravasation
Grade IV
Originally encompassed contained injuries to the main renal artery and vein, and collecting system injuries. Revision: adds segmental arterial and venous injury, and laceration to the renal pelvis or ureteropelvic junction. Multiple lacerations into the collecting system used to be considered a shattered kidney (Grade V), but now remains Grade IV.
Grade V
Originally included main renal artery or vein laceration or avulsion, and multiple collecting system lacerations (shattered kidney). The revised classification includes only vascular injury (arterial or venous) and includes laceration, avulsion or thrombosis.
http://onsurg.com/news/trauma-icu/aast-revises-renal-injury-grading
Radiology Reference 