Aast grading of renal injunry

Reading File

Finding Sources

Reading File

Here is a full breakdown of the AAST Organ Injury Scaling (OIS) system for renal trauma, based on the 2018 updated scale (Kozar et al., 2018) as cited in Sabiston Textbook of Surgery and Campbell Walsh Wein Urology:

AAST Renal Organ Injury Scale (2018 Update)

Grade	Description	AIS Severity
I	- Subcapsular hematoma or parenchymal contusion without laceration	2
II	- Perirenal hematoma confined to Gerota fascia	2
	- Renal laceration ≤1 cm depth without urinary extravasation
III	- Renal laceration >1 cm depth without urinary extravasation	3
	- Any injury with renal vascular injury or active bleeding contained within Gerota fascia
IV	- Parenchymal laceration with urinary extravasation	4
	- Renal pelvis laceration and/or ureteropelvic junction (UPJ) disruption
	- Active bleeding beyond Gerota fascia into retroperitoneum or peritoneum
	- Segmental or complete kidney infarction from vessel thrombosis (no active bleeding)
V	- Main renal artery or vein laceration or hilum avulsion	5
	- Devascularized kidney with active bleeding
	- Shattered kidney with loss of identifiable parenchymal anatomy

Note: Advance one grade for bilateral injuries up to Grade III.

Key Points

Original (1989) vs. Revised (2018) Grading

The original 1989 scale was based on surgical/anatomic findings.
The 2018 revision (Kozar et al.) incorporates radiologic (CT) findings and updates Grade IV and V to reflect contemporary management:
- Grade IV now includes: AV fistula/pseudoaneurysm, active bleeding beyond Gerota fascia, UPJ disruption, segmental vascular injury with infarction.
- Grade V now includes: devascularized kidney with active bleeding and shattered kidney without identifiable anatomy.

Clinical Relevance by Grade

Grade	Frequency	Management
I-III	~75-98% of all renal injuries	Conservative (observation); rarely need intervention
IV	Moderate	Usually managed with angioembolization + active surveillance
V	Least common	Highest rate of exploration and nephrectomy; surgical exploration carries ~64% nephrectomy rate

Surgery is currently needed in <10% of blunt renal injuries.
Penetrating injuries have a higher rate of operative intervention than blunt trauma.

Imaging Indications (AUA/EAU Guidelines)

All penetrating trauma with likely renal involvement in hemodynamically stable patients
All blunt trauma with:
- Gross hematuria, OR
- Microscopic hematuria + hemodynamic instability (systolic BP <90 mmHg), OR
- Significant deceleration mechanism (high-speed MVA, fall from height)
CT with IV contrast (immediate + delayed phases) is the gold standard

Important Note on Hematuria

Hematuria does not reliably correlate with injury severity:

Gross hematuria can occur in minor contusions
Hematuria may be absent in 7% of Grade IV injuries, 11% of gunshot wounds, and up to 36% of renal vascular injuries
~50% of UPJ injuries have no hematuria

Sources: Sabiston Textbook of Surgery (9780443124341), Campbell Walsh Wein Urology (9780323546423), Grainger & Allison's Diagnostic Radiology (9780323760751) - Kozar RA et al., J Trauma Acute Care Surg. 2018;85:1119-1122

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