What is the management approach for traumatic kidney injuries based on injury grade?

Traumatic Kidney Injury Grading and Management

Injury Classification

Traumatic kidney injuries are classified using the AAST Organ Injury Scale (Grades I-V) and managed primarily based on hemodynamic stability, with non-operative management being the standard approach for all stable patients regardless of injury grade. 1

AAST Grading System

• Grade I: Contusion with microscopic/gross hematuria and normal imaging, or subcapsular non-expanding hematoma without parenchymal laceration 1
• Grade II: Non-expanding perirenal hematoma confined to retroperitoneum, or cortical laceration <1 cm depth without urinary extravasation 1
• Grade III: Cortical laceration >1 cm depth without collecting system rupture or urinary extravasation 1
• Grade IV: Parenchymal laceration extending through cortex, medulla and collecting system, OR main renal artery/vein injury with contained hemorrhage, OR segmental vascular injuries 1
• Grade V: Completely shattered kidney OR avulsion of renal hilum that devascularizes kidney 1

WSES Clinical Classification

The WSES classification integrates hemodynamic status with AAST grades to guide management 1:

• WSES Class I (Minor): Hemodynamically stable AAST Grade I-II injuries
• WSES Class II (Moderate): Hemodynamically stable AAST Grade III injuries
• WSES Class III (Severe): Hemodynamically stable AAST Grade IV-V injuries or any grade with arterial dissection/occlusion
• WSES Class IV (Critical): Hemodynamically unstable AAST Grade I-V injuries (any grade)

Diagnostic Approach

Perform IV contrast-enhanced CT with immediate and delayed phases (10-15 minutes post-contrast) in all stable patients with gross hematuria, microscopic hematuria with systolic BP <90 mmHg, or concerning mechanism/physical findings (rapid deceleration, significant flank blow, rib fracture, flank ecchymosis, penetrating injury). 1

Key Diagnostic Considerations

• Hematuria does not predict injury severity: 10-25% of high-grade injuries and 24-50% of ureteropelvic junction injuries present without hematuria 1
• Delayed phase imaging is critical: Urinary leak is missed on initial CT in 1% of high-grade injuries 1, 2
• Children require imaging with >50 RBCs/HPF on urinalysis, plus consideration of mechanism and physical findings 1
• Up to 34% of multisystem trauma patients have renal injury despite absent hematuria or hypotension 1

Management Algorithm by Hemodynamic Status

Hemodynamically Stable Patients (WSES I-III)

Non-operative management is the standard of care for all hemodynamically stable patients regardless of injury grade, including high-grade (IV-V) injuries. 1

Non-Operative Management Requirements 1, 2:

• High-dependency/ICU environment with continuous hemodynamic monitoring
• Serial clinical examination and laboratory assessment (hemoglobin/hematocrit)
• Immediate access to interventional radiology, surgery, and blood products
• Bed rest until gross hematuria resolves 1, 2

Success Rates

• 93% of all renal injuries can be managed conservatively, including severe grades IV-V 3
• Non-operative management avoids unnecessary surgery, decreases nephrectomy rates, and preserves renal function 1

Hemodynamically Unstable Patients (WSES IV)

Immediate surgical exploration is mandatory for patients with persistent hemodynamic instability (SBP <90 mmHg with vasoconstriction, altered consciousness, or requiring ongoing transfusions/vasopressors despite resuscitation). 1

Absolute Surgical Indications 2:

• Hemodynamic instability unresponsive to fluid resuscitation
• Peritonitis
• Expanding or pulsatile hematoma
• Failed angioembolization with persistent bleeding
• Complete ureteropelvic junction avulsion (select cases)

Relative Surgical Indications 2:

• Incomplete staging of injury
• Associated injuries requiring laparotomy

Role of Angioembolization

Angioembolization should be performed for ongoing bleeding in hemodynamically stable or transiently responsive patients, with super-selective technique achieving 63-100% success rates. 2, 4

Indications for Angioembolization 2, 5:

• Active contrast extravasation on CT (arterial blush)
• Pseudoaneurysm formation
• Arteriovenous fistula
• Persistent bleeding despite initial resuscitation
• Significant hemoglobin drop with perinephric hematoma

Technical Approach

• Super-selective embolization preserves maximum renal parenchyma 2, 4
• Allows continuation of non-operative management if hemodynamic recovery occurs post-procedure 2

Management of Collecting System Injuries

Collecting system injuries (Grade IV) require close monitoring with repeat CT at 48-72 hours, as urinary leak may be missed initially; intervention is reserved for symptomatic or enlarging urinomas. 1, 2

Follow-up Protocol for High-Grade Injuries 1, 2:

• Repeat CT with delayed phase within 48-72 hours for AAST Grade IV-V injuries
• Asymptomatic stable collections can continue conservative management
• Moderate injuries (Grade III) without extravasation require imaging only if clinical status worsens

Indications for Urological Intervention 2:

• Enlarging urinoma
• Fever or infection
• Increasing pain
• Ileus
• Fistula formation
• Non-resolving symptomatic urinoma

Endoscopic Management

• Ureteral stenting is first-line intervention when drainage becomes necessary (required in 14-20% of collecting system injuries) 2
• Percutaneous drainage for infected or enlarging urinomas 2
• Complete ureteropelvic junction avulsion may require acute or delayed surgical repair 2

Monitoring for Complications

Secondary hemorrhage from pseudoaneurysm or arteriovenous fistula occurs in up to 25% of moderate/severe injuries within 2 weeks, with hematuria being the most common presenting sign. 1, 2

Surveillance Strategy 1, 2:

• New or worsening hematuria warrants immediate contrast-enhanced CT, Doppler ultrasound, or contrast-enhanced ultrasound
• These three modalities show similar reliability for detecting vascular complications 1
• Low-grade injuries (I-II) have very low complication rates and do not require routine follow-up imaging 1

Return to Activity Guidelines

Sports activities must be avoided until microscopic hematuria resolves, with return to activity timing based on injury severity. 1, 2

Activity Restrictions 1, 2:

• Minor/moderate injuries (Grades I-III): 2-6 weeks before return to sports
• Severe injuries (Grades IV-V): 6-12 months before return to sports
• Bed rest or reduced activity until gross hematuria resolves for all grades

Critical Pitfalls to Avoid

• Never attempt non-operative management without immediate access to interventional radiology, surgery, and blood products 1, 2
• Do not miss complete ureteropelvic junction avulsion, which often requires surgical repair despite hemodynamic stability 2
• Do not rely on presence or absence of hematuria to exclude significant injury—mechanism and physical findings are equally important 1
• Do not skip delayed-phase imaging in suspected renal trauma, as collecting system injuries will be missed 1, 2
• Transient responders to resuscitation (initial response followed by deterioration) should be managed as hemodynamically unstable 1

Pediatric Considerations

• Children are more vulnerable to renal injury due to less perirenal fat, thinner abdominal muscles, incomplete rib ossification, and larger kidney-to-body ratio 1
• Hemodynamic instability in children is defined as failure to respond to 3 boluses of 20 mL/kg crystalloid (lack of heart rate reduction, persistent altered sensorium, absent peripheral pulses) 1
• Ultrasound or contrast-enhanced ultrasound may be used for follow-up in children to minimize radiation, though CT remains preferred for initial evaluation 1