Apply the benign-feature and cancer-history precedence before size. Return the exact source branch and required safety caveats; the 2017 algorithm is guidance, not an autonomous diagnosis or treatment order.
{
"applicability": {
"use_for": "Incidentally detected adrenal mass on CT or MRI in an asymptomatic adult (age >=18 years) imaged for a reason unrelated to possible adrenal disease.",
"bilateral_rule": "Assess each adrenal lesion separately.",
"generally_do_not_pursue": "Short-axis size <1 cm unless clinical circumstances warrant evaluation.",
"do_not_apply_when": [
"symptoms_or_signs_are_attributable_to_adrenal_disease",
"the_mass_is_not_incidental",
"workup_cannot_change_management_due_to_comorbidity_or_limited_life_expectancy"
]
},
"categories": [
{
"outcome_code": "macroscopic-fat",
"role": "specific_benign_subtype",
"defining_feature": "macroscopic_fat_consistent_with_myelolipoma"
},
{
"outcome_code": "benign-features",
"role": "leave_alone_endpoint",
"defining_features": [
"unenhanced_CT_<=10_HU",
"chemical_shift_signal_loss_relative_to_spleen",
"no_enhancement_cyst_or_hemorrhage",
"benign_calcification"
]
},
{
"outcome_code": "prior-malignancy",
"role": "clinical_context_branch",
"defining_feature": "known_cancer_and_no_diagnostic_benign_feature"
},
{
"outcome_code": "large-mass",
"role": "size_branch_without_cancer",
"defining_feature": "isolated_indeterminate_mass_>=4_cm"
},
{
"outcome_code": "indeterminate",
"role": "characterization_or_follow_up_branch",
"defining_feature": "no_diagnostic_benign_feature_and_not_resolved_by_precedence_rules"
}
],
"category_precedence": [
"If macroscopic fat is present, use macroscopic-fat as the specific benign endpoint.",
"Otherwise, diagnostic benign imaging features route to benign-features regardless of size.",
"For a non-benign mass, known malignancy routes to prior-malignancy before the no-cancer size branches.",
"Without cancer history, an indeterminate isolated mass >=4 cm routes to large-mass; smaller masses route to indeterminate."
],
"diagnostic_definitions": {
"lipid_rich_adenoma": {
"unenhanced_CT_HU": "<=10",
"endpoint": "benign-features"
},
"chemical_shift_adenoma": {
"finding": "signal_loss_relative_to_spleen_between_in_phase_and_opposed_phase",
"endpoint": "benign-features"
},
"no_enhancement": {
"formula": "postcontrast_HU - precontrast_HU",
"threshold": "<10_HU_change",
"interpretation": "cyst_or_hemorrhage",
"endpoint": "benign-features"
},
"macroscopic_fat": {
"interpretation": "myelolipoma",
"endpoint": "macroscopic-fat"
},
"absolute_percentage_washout": {
"formula": "100 * (enhanced_HU - 15_min_delayed_HU) / (enhanced_HU - unenhanced_HU)",
"adenoma_threshold": ">=60_percent"
},
"relative_percentage_washout": {
"formula": "100 * (enhanced_HU - 15_min_delayed_HU) / enhanced_HU",
"use_when": "unenhanced_value_unavailable",
"adenoma_threshold": ">=40_percent"
},
"isolated": "No other metastatic disease identified."
},
"branches": [
{
"id": "prior_stability",
"condition": "stable_for_>=1_year",
"action": "benign_no_additional_imaging",
"outcome_code": "benign-features"
},
{
"id": "no_cancer_1_to_2_cm",
"condition": "indeterminate_1_to_2_cm_no_prior_imaging_no_cancer_history",
"action": "consider_adrenal_CT_follow_up_at_12_months_for_stability",
"outcome_code": "indeterminate"
},
{
"id": "no_cancer_>2_to_<4_cm",
"condition": "indeterminate_>2_to_<4_cm_no_prior_imaging_no_cancer_history",
"action": "dedicated_adrenal_CT_at_detection",
"outcome_code": "indeterminate"
},
{
"id": "still_indeterminate_after_protocol",
"condition": "APW_<60_percent_and_RPW_<40_percent_or_otherwise_uncharacterized",
"action": "imaging_follow_up_biopsy_PET_CT_or_resection_according_to_clinical_scenario",
"outcome_code": "indeterminate"
},
{
"id": "new_or_enlarging_no_cancer",
"condition": "new_or_enlarging_indeterminate_mass_without_cancer_history",
"action": "biochemical_evaluation_then_follow_up_adrenal_CT_or_resection_according_to_growth_and_context",
"outcome_code": "indeterminate"
},
{
"id": "isolated_>=4_cm_no_cancer",
"condition": "isolated_indeterminate_mass_>=4_cm_without_cancer_history",
"action": "consider_resection_without_biopsy_for_possible_adrenocortical_carcinoma",
"outcome_code": "large-mass"
},
{
"id": "known_cancer_1_to_<4_cm",
"condition": "indeterminate_mass_1_to_<4_cm_known_cancer_no_prior_stability",
"action": "dedicated_adrenal_CT_without_and_with_contrast",
"outcome_code": "prior-malignancy"
},
{
"id": "known_cancer_escalation",
"condition": "new_enlarging_necrotic_still_indeterminate_or_>=4_cm_in_oncology_patient",
"action": "consider_FDG_PET_CT_or_image_guided_biopsy_for_presumed_metastasis",
"outcome_code": "prior-malignancy"
}
],
"safety": [
"Consider biochemical assays for functional status for most incidental adrenal masses.",
"Exclude pheochromocytoma before biopsy or resection; obtain plasma metanephrines when it is suspected.",
"Imaging characterization does not determine whether an adenoma is hyperfunctioning.",
"Contrast-enhanced CT alone cannot reliably distinguish an adenoma from metastasis in a patient with cancer; use the dedicated pathway."
],
"required_inputs": [
"adult_and_asymptomatic_status",
"short_axis_size_cm",
"unenhanced_HU_or_reason_unavailable",
"enhancement_or_washout_when_available",
"macroscopic_fat_or_other_benign_features",
"prior_imaging_and_stability",
"known_malignancy",
"other_metastatic_disease",
"clinical_functional_signs"
],
"missing_input_behavior": [
"Do not select a definitive branch without cancer history, size and benign-feature status; return the missing inputs.",
"Do not calculate washout when a required attenuation value or the 15-minute delay is absent.",
"Do not recommend biopsy without the pheochromocytoma safety warning."
],
"version_context": {
"implemented_system": "ACR Incidental Findings Committee adrenal white paper, 2017",
"current_adjacent_document": "ACR Appropriateness Criteria Adrenal Mass Evaluation, 2021",
"rule": "Keep the 2017 IFC algorithm version explicit; do not silently substitute a different society guideline or the adjacent ACR procedure-appropriateness document."
},
"source_locator": "Mayo-Smith et al., JACR 2017;14:1038-1044, Fig. 1; pp.4-6 for applicability, size branches, washout formulas, PET/CT, biopsy and endocrine evaluation. ACR Appropriateness Criteria Adrenal Mass Evaluation (2021) reviewed for version context."
}