Renal injuries are graded by the American Association for the Surgery of Trauma in 5 grades:

– Grade 1 – Renal contusion or nonexpanding subcapsular hematoma without a parenchymal laceration

– Grade 2 – Nonexpanding perirenal hematoma or a renal cortex laceration (< 1 cm) without urinary extravasation

– Grade 3 – Renal cortex laceration (>1 cm) and no urinary extravasation

– Grade 4 – Renal cortical laceration extending into the collecting system (contrast extravasation), or a segmental renal artery or vein injury (parenchymal infarct), or main renal artery or vein injury with a contained hematoma

– Grade 5 – Shattered kidney, avulsion of the renal pedicle, or thrombosis of the main renal artery
Injuries grade 1 – 3 are usually managed conservatively, grade 4 – 5 are usually explored / managed in theatre.