AAST Liver Organ Injury Scale

{
  "categories": [
    {
      "outcome_code": "I",
      "any_of": [
        "subcapsular_hematoma_less_than_10_percent_surface_area",
        "capsular_tear_or_parenchymal_laceration_less_than_1_cm_depth"
      ]
    },
    {
      "outcome_code": "II",
      "any_of": [
        "subcapsular_hematoma_10_to_50_percent_surface_area",
        "intraparenchymal_hematoma_less_than_10_cm_diameter",
        "laceration_1_to_3_cm_depth_and_10_cm_or_less_length"
      ]
    },
    {
      "outcome_code": "III",
      "any_of": [
        "subcapsular_hematoma_greater_than_50_percent_or_ruptured",
        "intraparenchymal_hematoma_10_cm_or_larger_or_ruptured",
        "laceration_greater_than_3_cm_depth",
        "contained_hepatic_vascular_injury_or_active_bleeding_within_parenchyma"
      ]
    },
    {
      "outcome_code": "IV",
      "any_of": [
        "parenchymal_disruption_25_to_75_percent_of_one_lobe",
        "parenchymal_disruption_1_to_3_Couinaud_segments_within_one_lobe",
        "active_bleeding_extending_beyond_parenchyma_into_peritoneum"
      ]
    },
    {
      "outcome_code": "V",
      "any_of": [
        "parenchymal_disruption_greater_than_75_percent_of_one_lobe",
        "parenchymal_disruption_more_than_3_Couinaud_segments_within_one_lobe",
        "juxtahepatic_venous_injury_to_retrohepatic_IVC_or_central_major_hepatic_veins"
      ]
    }
  ],
  "applicability": {
    "intended_use": "Standardized anatomic grading of traumatic liver injury using imaging, operative or pathologic findings.",
    "classification_unit": "one_liver_injury_episode_using_the_highest_supported_finding",
    "required_inputs": [
      "contrast_enhanced_multiphase_CT_when_imaging_is_used",
      "hematoma_location_and_size",
      "laceration_depth_and_length",
      "parenchymal_disruption_extent",
      "vascular_injury_and_active_bleeding_location",
      "operative_or_pathologic_findings_when_available"
    ],
    "outside_scope": [
      "grading_nontraumatic_liver_disease",
      "hemodynamic_classification",
      "automatic_nonoperative_or_operative_selection",
      "individual_mortality_or_failure_probability"
    ]
  },
  "assignment_algorithm": [
    "Confirm traumatic mechanism, study adequacy and whether the source is imaging, surgery or pathology.",
    "Describe every hematoma, laceration, disruption and vascular or bleeding finding with the measurements and contrast phase needed for the applicable branch.",
    "Assign the highest grade supported by any imaging, operative or pathologic criterion; do not average discordant findings.",
    "For multiple grade I or II injuries, advance one grade only, with the multiple-injury upgrade capped at grade III.",
    "Return hemodynamic status, transfusion or resuscitation trajectory, associated injuries and local resources separately from the anatomic grade."
  ],
  "measurement_and_imaging_protocol": {
    "hematoma": "Report subcapsular surface-area percentage or maximum intraparenchymal diameter and whether the hematoma is ruptured. Do not translate one measurement type into the other.",
    "laceration": "Measure maximum parenchymal depth perpendicular to the capsule and record length when the grade-II 10-cm boundary is relevant. Exactly 1 cm enters grade II; exactly 3 cm remains grade II; greater than 3 cm enters grade III.",
    "parenchymal_disruption": "Use percentage of a single lobe or number of Couinaud segments within a single lobe. State which method and lobe were used rather than summing both descriptions.",
    "active_bleeding": "Distinguish active contrast extravasation contained within liver parenchyma, which supports grade III, from free extension beyond the parenchyma into the peritoneum, which supports grade IV.",
    "vascular_injury": "Contained pseudoaneurysm or arteriovenous fistula supports grade III; juxtahepatic venous injury involving the retrohepatic IVC or central major hepatic veins supports grade V.",
    "adequacy": "A single phase, motion, incomplete liver coverage or absent intravenous contrast may prevent confident assessment of bleeding or vascular injury; preserve that limitation."
  },
  "decisive_boundaries": {
    "grade_I_to_II_hematoma": "Subcapsular involvement below 10 percent is I; exactly 10 percent through 50 percent is II.",
    "grade_II_to_III_subcapsular": "Exactly 50 percent remains II; greater than 50 percent or rupture is III.",
    "grade_II_to_III_laceration": "A laceration exactly 3 cm deep may remain II when its length is 10 cm or less; depth greater than 3 cm is III.",
    "grade_III_to_IV_bleeding": "Active bleeding contained within parenchyma is III; active bleeding extending beyond the liver into the peritoneum is IV.",
    "grade_IV_to_V_disruption": "Twenty-five to 75 percent of one lobe or one to three segments is IV; greater than 75 percent or more than three segments in one lobe is V.",
    "multiple_injuries": "Multiple lower-grade injuries cause at most a one-grade increase and never use this rule to exceed III."
  },
  "management_boundary": {
    "hemodynamically_stable": "WSES guidance supports nonoperative management for stable patients across AAST grades I-V when no other injury requires laparotomy and appropriate monitoring, interventional radiology, operating-room access and blood products are available.",
    "arterial_blush": "In an otherwise stable adult, arterial blush or pseudoaneurysm can support angiography and angioembolization consideration; pediatric practice and local protocols may differ. The grade is not itself an embolization order.",
    "unstable_or_nonresponder": "Hemodynamic instability or nonresponse to resuscitation, not a grade numeral alone, drives urgent operative hemorrhage control and damage-control decisions.",
    "associated_injuries": "Peritonitis, hollow-viscus injury, diaphragm or biliary injury and other operative indications can change management independently of the liver grade.",
    "complications": "Bile leak, biloma, hemobilia, pseudoaneurysm, delayed hemorrhage, necrosis and abscess require separate surveillance and targeted treatment; none is fully encoded by the initial grade."
  },
  "risk_interpretation": {
    "population_gradient": "Higher anatomic grade is associated with greater injury burden in cohorts, but no grade provides a portable individual probability of death, nonoperative failure, transfusion or complication.",
    "stronger_patient_axes": [
      "hemodynamic_response",
      "associated_injury_burden",
      "age_and_comorbidity",
      "coagulopathy_and_transfusion_need",
      "time_since_injury",
      "center_resources"
    ],
    "prohibited_inferences": [
      "grade_IV_or_V_requires_surgery",
      "grade_I_or_II_is_clinically_safe_without_monitoring",
      "universal_nonoperative_failure_percentage",
      "individual_mortality_percentage"
    ]
  },
  "system_boundaries": {
    "WSES": "WSES combines AAST anatomy with hemodynamic status into a separate management classification. Do not relabel a WSES class as an AAST grade.",
    "BCLC_or_LI_RADS": "Tumor staging and liver-lesion reporting systems are unrelated to traumatic organ-injury grading despite sharing the organ name."
  },
  "agent_output_contract": [
    "Return imaging or operative source and technical adequacy.",
    "List each injury feature with its raw measurement and contrast-phase evidence.",
    "Return the highest supporting criterion, multiple-injury rule if used and final AAST grade I-V.",
    "Return hemodynamics, associated injuries and active-bleeding state as separate management inputs.",
    "Separate anatomic grade from treatment recommendation and patient-specific prognosis."
  ],
  "missing_input_behavior": [
    "Without adequate contrast-enhanced imaging or operative findings, do not infer absence of vascular injury or active bleeding.",
    "If a measurement straddles a threshold, return both adjacent possible grades and the measurement uncertainty.",
    "If free versus contained active bleeding is unclear, withhold the III-versus-IV decision and recommend source review or adequate repeat imaging according to clinical urgency.",
    "If hemodynamic status is absent, return the anatomic grade but explicitly withhold management-pathway selection."
  ],
  "supporting_sources": [
    {
      "role": "current_scale",
      "citation": "Kozar et al. J Trauma Acute Care Surg. 2018;85:1119-1122",
      "doi": "10.1097/TA.0000000000002058"
    },
    {
      "role": "current_management_context",
      "citation": "Coccolini et al. World J Emerg Surg. 2020;15:24",
      "doi": "10.1186/s13017-020-00302-7",
      "pmcid": "PMC7106618"
    }
  ],
  "source_locator": "Kozar et al. 2018, DOI 10.1097/TA.0000000000002058, revised liver table and footnotes; Coccolini et al. 2020, PMC7106618, classification, nonoperative, angioembolization and operative-management recommendations."
}