The revision is a shift from pure anatomical description toward prediction of the need for a bleeding-control intervention. The authors recognise that conservative management is now the default across all grades, and that imaging (rather than laparotomy) is the universal first-line assessment. The grade should tell you who is likely to need embolisation, stenting, or surgery — not just describe what the parenchyma looks like.
As with previous iterations, the new scale retains three sets of criteria — radiological, operative, and pathological — with the highest of the three assigning the final grade. In practice, radiological criteria now dominate, reflecting the near-universal use of multiphasic CT in the initial assessment of renal trauma, but the operative and pathological descriptors remain if the kidney is explored, resected, or examined post-mortem.
The 1 cm threshold between Grade II and III was expert opinion. New data on laceration length and bleeding risk support a 2.5 cm axial cut-off, measured on a single axial CT image at its longest extent.
More than 70% of urinary leaks resolve spontaneously, and the rest are usually handled with a ureteric stent rather than open surgery. It no longer belongs in the same category as injuries requiring operative intervention. The exception — complete or near-complete ureteropelvic junction disruption — remains Grade IV because it almost always needs early open or endoscopic intervention.
Isolated segmental infarcts almost never need intervention and usually heal with scarring alone. Only complete or near-complete devascularisation (>95%) remains Grade IV (or V with active bleeding).
Pseudoaneurysm, AV fistula, dissection, thrombosis, intimal flap, and mural haematoma — all contained, non-bleeding vascular injuries — are now grouped together at Grade III. Uncontained injuries (laceration or transection with active bleeding) are Grade IV or V.
The old term was vague and its inflammatory connotation drove unnecessary nephrectomies. MFK is now clearly defined as three or more parenchymal fragments displaced by fluid or blood. MFK without active bleeding is Grade IV; MFK with active bleeding is Grade V.
A subcapsular haematoma under 3.5 cm without active bleeding is Grade I. A haematoma rim distance (HRD) of 3.5 cm or more promotes the injury to Grade III. A new concept — pararenal haematoma — describes medial extension past the lateral border of the IVC (right) or aorta (left), or inferior extension past the aortic bifurcation, and automatically pushes the injury to Grade IV.
| Grade | Imaging hallmark (no active bleeding unless stated) |
|---|---|
| I | Subcapsular haematoma <3.5 cm, or contusion |
| II | Laceration <2.5 cm, HRD <3.5 cm |
| III | Laceration ≥2.5 cm, HRD ≥3.5 cm, partial infarct, contained vascular injury, urinary extravasation |
| IV | Active bleeding, pararenal haematoma, complete infarct (no bleed), MFK (no bleed), complete UPJ disruption |
| V | Main renal artery/vein laceration or transection with active bleeding; complete infarct or MFK with active bleeding |
When the Keihani group retrospectively re-graded their multi-institutional cohort using the new system, 60% of patients were downgraded — with nearly 70% of old Grade IVs moving down to Grade III. The most likely exam traps are:
It is also worth keeping in mind what the update does not change: each kidney is still graded separately in bilateral injury, the highest of radiological, operative, or pathological criteria still assigns the final grade, and multiple Grade I–II injuries are no longer upgraded to a higher grade. Management principles also remain the same — the vast majority of blunt renal injuries are managed conservatively, with angioembolisation for active bleeding in the stable patient and surgical exploration reserved for haemodynamic instability.
It is not yet clear if and when examiners will adopt the 2025 criteria. The 2018 scale remains in widespread clinical use and is still the version referenced in the current EAU Urological Trauma guidelines. The EAU 2026 guidance explicitly states: "The references in this text are still based on the AAST 1989 renal injury scale. The 2018 injury scale does not outperform the previous grading system in predicting bleeding and the need for treatment intervention."
That said, the 2025 classification rests on a more solid evidence foundation, clarifies previously vague areas (the definition of shattered kidney being the obvious example), and pragmatically aims to reduce the proportion of injuries labelled as high grade that would be managed conservatively regardless. It seems reasonable that this will become widespread, and candidates should at least be aware of these changes.
For that reason we are currently including questions based on both the 2018 and 2025 classifications, with a view to phasing out the 2018 questions once the new scale is fully established in guidelines and teaching.
Urobank questions are updated to reflect the latest evidence, so you're never caught out by a classification change.