How are liver lacerations graded?

Liver Laceration Grading Systems

Liver lacerations are graded using two complementary systems: the anatomic AAST (American Association for the Surgery of Trauma) classification (Grades I-VI) and the WSES (World Society of Emergency Surgery) classification that integrates both anatomic injury and hemodynamic status.

AAST Anatomic Grading System

The AAST classification grades liver injuries from I to VI based purely on anatomical severity 1:

Grade I (Minimal)

• Hematoma: Subcapsular <10% surface area 1
• Laceration: Capsular tear <1 cm parenchymal depth 1

Grade II (Minor)

• Hematoma: Subcapsular 10-50% surface area; intraparenchymal <10 cm diameter 1
• Laceration: 1-3 cm parenchymal depth, <10 cm in length 1

Grade III (Moderate)

• Hematoma: Subcapsular >50% surface area or expanding/ruptured subcapsular or parenchymal hematoma; intraparenchymal hematoma >10 cm 1
• Laceration: >3 cm parenchymal depth 1

Grade IV (Severe)

• Laceration: Parenchymal disruption involving 25-75% of hepatic lobe 1
• Vascular: Juxtavenous hepatic injuries (retrohepatic vena cava/central major hepatic veins) 1

Grade V (Critical)

• Laceration: Parenchymal disruption >75% of hepatic lobe 1
• Vascular: Juxtavenous hepatic injuries 1

Grade VI (Unsurvivable)

• Vascular: Hepatic avulsion 1

Important caveat: Multiple injuries advance the grade by one level up to Grade III 1.

WSES Classification: Integrating Hemodynamics

The WSES classification addresses a critical limitation of the AAST system by incorporating hemodynamic stability, which fundamentally changes management decisions 1:

WSES Grade I (Minor)

• AAST Grade I-II injuries in hemodynamically stable patients (blunt or penetrating) 1

WSES Grade II (Moderate)

• AAST Grade III injuries in hemodynamically stable patients (blunt or penetrating) 1

WSES Grade III (Severe)

• AAST Grade IV-VI injuries in hemodynamically stable patients (blunt or penetrating) 1

WSES Grade IV (Severe/Critical)

• Any AAST grade (I-VI) in hemodynamically unstable patients (blunt or penetrating) 1

Critical Clinical Principle

Hemodynamic status trumps anatomic grade in determining management. A "minor" AAST Grade I-II injury becomes WSES Grade IV (requiring operative management) if the patient is hemodynamically unstable, while even severe AAST Grade IV-V injuries can be managed nonoperatively if the patient remains stable 1.

Hemodynamic Instability Defined

Per ATLS criteria, instability includes 1:

• Blood pressure <90 mmHg **and** heart rate >120 bpm
• Evidence of skin vasoconstriction (cool, clammy skin, decreased capillary refill)
• Altered level of consciousness
• Shortness of breath

Management Implications by Grade

For Hemodynamically Stable Patients (WSES I-III)

• Non-operative management should be attempted regardless of AAST grade 1, 2
• Requires intensive monitoring with serial clinical examination, laboratory evaluation, and CT imaging 1, 2
• Must have immediate access to interventional radiology, operating room, and blood products 1, 2

For Hemodynamically Unstable Patients (WSES IV)

• Immediate operative management required regardless of anatomic injury grade 1
• No additional imaging should delay surgical intervention 2

Common Pitfalls to Avoid

• Never assume high-grade AAST injuries (IV-V) automatically require surgery—up to 85-90% of blunt liver injuries can be managed nonoperatively if hemodynamically stable 3, 4
• Never attempt nonoperative management in facilities lacking immediate surgical/interventional capabilities—transfer to appropriate center instead 1, 2
• CT grading frequently misclassifies operative injury severity—84% of CT grades did not correlate with operative findings in one study, with particular difficulty around the falciform ligament 5
• Beware of delayed failure of nonoperative management—failure rates reach 46.7% for AAST Grade III-V injuries, with 50% mortality when Grade IV-V injuries fail 6