Todani classification of congenital bile duct cysts

{
  "categories": [
    {
      "outcome_code": "I",
      "anatomic_domain": "extrahepatic_bile_duct",
      "definition": "solitary_fusiform_or_cystic_extrahepatic_dilatation",
      "classical_subtypes": [
        "Ia_entire_extrahepatic_cystic_dilatation",
        "Ib_focal_segmental_extrahepatic_dilatation",
        "Ic_smooth_fusiform_extrahepatic_dilatation_with_anomalous_pancreaticobiliary_junction_often_present"
      ]
    },
    {
      "outcome_code": "II",
      "anatomic_domain": "extrahepatic_bile_duct",
      "definition": "true_diverticulum_arising_from_extrahepatic_duct_with_discrete_neck"
    },
    {
      "outcome_code": "III",
      "anatomic_domain": "distal_intramural_common_bile_duct",
      "definition": "choledochocele_cystic_dilatation_within_duodenal_wall_protruding_toward_duodenal_lumen"
    },
    {
      "outcome_code": "IV",
      "anatomic_domain": "multiple_biliary_segments",
      "definition": "multiple_congenital_bile_duct_dilatations",
      "classical_subtypes": [
        "IVa_intrahepatic_and_extrahepatic_dilatations",
        "IVb_multiple_extrahepatic_dilatations_only"
      ]
    },
    {
      "outcome_code": "V",
      "anatomic_domain": "intrahepatic_bile_ducts_only",
      "definition": "Caroli_disease_segmental_saccular_or_fusiform_intrahepatic_duct_dilatation_communicating_with_biliary_tree"
    }
  ],
  "applicability": {
    "use_for": "Anatomic classification of a congenital bile duct cyst or congenital duct ectasia after the distribution and communication of every dilated segment have been mapped.",
    "classification_unit": "one_patient_level_congenital_biliary_malformation_with_subtype_and_distribution_preserved",
    "required_inputs": [
      "intrahepatic_duct_involvement",
      "extrahepatic_duct_involvement_and_morphology",
      "number_of_dilated_segments",
      "distal_intramural_or_intraduodenal_component",
      "communication_with_biliary_tree",
      "gallbladder_and_cystic_duct_anatomy",
      "pancreaticobiliary_junction_when_visible",
      "strictures_stones_masses_and_complications"
    ],
    "outside_scope": [
      "secondary_obstructive_bile_duct_dilatation",
      "primary_sclerosing_cholangitis",
      "postoperative_or_ischemic_strictures",
      "isolated_gallbladder_or_simple_hepatic_cyst",
      "peribiliary_cysts_without_duct_communication",
      "treatment_selection_without_specialist_review"
    ]
  },
  "full_biliary_mapping_gate": {
    "mandatory_before_classification": "Trace the right and left intrahepatic ducts, hilum, common hepatic duct, cystic duct insertion, extrahepatic duct, intrapancreatic segment and ampullary or intraduodenal segment; a single enlarged duct measurement is insufficient.",
    "congenital_pattern_support": [
      "disproportionate_nonobstructive_cystic_or_fusiform_dilatation",
      "direct_communication_with_biliary_lumen",
      "anomalous_pancreaticobiliary_junction_or_long_common_channel_when_demonstrated",
      "central_dot_sign_for_Caroli_pattern",
      "absence_of_a_better_downstream_obstructing_cause"
    ],
    "exclusion_checks": [
      "stone_or_sludge",
      "benign_or_malignant_stricture",
      "pancreatic_or_ampullary_mass",
      "cholangiocarcinoma_or_gallbladder_cancer",
      "PSC_or_recurrent_pyogenic_cholangitis",
      "postoperative_or_transplant_change",
      "portal_hypertension_related_peribiliary_cysts"
    ],
    "failure_rule": "If complete duct distribution or a credible obstructing cause cannot be assessed, report the mapped anatomy and differential and withhold a definitive Todani type."
  },
  "anatomic_subtype_map": {
    "type_I": {
      "Ia": "Marked cystic dilatation involving essentially the entire extrahepatic duct; distinguish a true cystic duct lumen from an adjacent noncommunicating cyst.",
      "Ib": "Focal segmental diverticular or saccular dilatation of the extrahepatic duct without the narrow-necked true diverticulum morphology of type II.",
      "Ic": "Diffuse smooth fusiform dilatation of the extrahepatic duct, often extending continuously toward the pancreaticobiliary junction; the 2003 clarification emphasizes the distal duct and primary-duct-stricture anatomy.",
      "boundary": "A single extrahepatic cystic or fusiform channel is I; multiple distinct extrahepatic cysts are IVb, and a discrete true diverticulum from an otherwise near-normal duct is II."
    },
    "type_IV": {
      "IVa": "Multiple dilatations involving both intrahepatic and extrahepatic ducts; document intrahepatic extent, dominant strictures and lobar distribution rather than using IV alone.",
      "IVb": "Multiple dilatations confined to the extrahepatic tree with no congenital intrahepatic component.",
      "boundary": "Any genuine congenital intrahepatic component plus extrahepatic disease is IVa; extrahepatic multiplicity alone is IVb; intrahepatic disease alone is V."
    },
    "type_V": {
      "Caroli_disease": "Pure ductal-plate malformation with communicating segmental saccular or fusiform intrahepatic duct ectasia and no extrahepatic cyst.",
      "Caroli_syndrome": "Caroli-pattern intrahepatic duct ectasia plus congenital hepatic fibrosis and portal-hypertension features; retain this phenotype separately because Todani V alone does not encode the fibrosis.",
      "central_dot_sign": "A portal-radicle bundle traversing a dilated intrahepatic duct supports Caroli morphology but is not by itself sufficient when obstruction or other mimics remain possible."
    }
  },
  "assignment_algorithm": [
    {
      "priority": 1,
      "if": "dilatation_confined_to_intramural_or_intraduodenal_distal_common_bile_duct",
      "output_code": "III"
    },
    {
      "priority": 2,
      "if": "true_extrahepatic_diverticulum_with_discrete_neck_and_otherwise_nondilated_or_near_normal_duct",
      "output_code": "II"
    },
    {
      "priority": 3,
      "if": "multiple_congenital_dilatations_in_both_intrahepatic_and_extrahepatic_ducts",
      "output_code": "IV",
      "mandatory_subtype": "IVa"
    },
    {
      "priority": 4,
      "if": "multiple_congenital_dilatations_confined_to_extrahepatic_ducts",
      "output_code": "IV",
      "mandatory_subtype": "IVb"
    },
    {
      "priority": 5,
      "if": "single_cystic_or_fusiform_extrahepatic_dilatation_without_congenital_intrahepatic_disease",
      "output_code": "I",
      "mandatory_subtype": "Ia_or_Ib_or_Ic_when_resolvable"
    },
    {
      "priority": 6,
      "if": "communicating_congenital_intrahepatic_duct_ectasia_without_extrahepatic_cyst",
      "output_code": "V"
    }
  ],
  "imaging_strategy": {
    "ultrasound": "Common first examination, especially in children: establish cystic continuity with the biliary tract, gallbladder separation, intrahepatic involvement, stones and upstream dilatation; bowel gas can limit distal mapping.",
    "MRCP": "Preferred noninvasive whole-tree map for intrahepatic and extrahepatic distribution, duct communication, strictures, stones and pancreaticobiliary junction when visible; retain limitations from motion, small caliber and prior intervention.",
    "contrast_MRI_or_CT": "Characterize wall thickening, enhancement, mass, pancreatitis, cholangitis, vascular anatomy and complications; CT also helps emergency evaluation but ionizing radiation matters in children.",
    "ERCP": "Invasive and generally reserved for unresolved distal or junctional anatomy, choledochocele assessment, sampling or therapeutic intervention; it is not required solely to attach a Todani label when noninvasive mapping is adequate.",
    "operative_cholangiography": "May resolve duct connections or strictures that remain uncertain preoperatively; distinguish imaging-suspected from surgically confirmed anatomy."
  },
  "differential_and_exclusion": [
    "Do not classify ordinary upstream dilatation from a stone, tumor, inflammatory stricture or postoperative injury as a congenital bile duct cyst.",
    "Differentiate type II from gallbladder duplication, cystic-duct diverticulum, pancreatic pseudocyst, enteric duplication cyst and noncommunicating hepatic cyst by direct duct communication and neck anatomy.",
    "Differentiate type III choledochocele from duodenal duplication cyst, periampullary diverticulum and obstructive ampullary lesion.",
    "Differentiate type V from primary sclerosing cholangitis, recurrent pyogenic cholangitis, obstructive saccular change and peribiliary cysts; communication with the duct lumen and distribution are decisive.",
    "A cystic-duct-only lesion proposed as type VI and a forme-fruste extrahepatic pattern are described variants outside the original I-V outcome set; name the anatomy and the convention instead of silently forcing a classical code."
  ],
  "associated_features_and_complications": {
    "report": [
      "maximal_dimensions_and_longitudinal_extent",
      "intrahepatic_lobar_distribution",
      "dominant_strictures",
      "stones_or_sludge",
      "cholangitis_or_abscess",
      "pancreatitis",
      "wall_thickening_nodule_or_mass",
      "gallbladder_abnormality",
      "pancreaticobiliary_junction",
      "congenital_hepatic_fibrosis_and_portal_hypertension",
      "prior_drainage_resection_or_reconstruction"
    ],
    "urgent_flags": [
      "sepsis_or_acute_cholangitis",
      "biliary_obstruction",
      "cyst_rupture_or_bile_peritonitis",
      "acute_pancreatitis",
      "suspicious_enhancing_mural_lesion_or_stricture"
    ],
    "safety_rule": "The Todani code does not replace a complication statement; acute obstruction, infection, rupture, pancreatitis or suspected malignancy must be surfaced directly."
  },
  "management_context_by_type": {
    "I": "Specialist literature generally favors complete extrahepatic cyst excision with cholecystectomy and bilioenteric reconstruction when feasible; anatomy, age, inflammation and prior surgery govern the actual plan.",
    "II": "A true diverticulum is commonly considered for diverticulectomy, with duct repair or reconstruction determined by neck width and duct integrity; the imaging code alone cannot select the operation.",
    "III": "Endoscopic sphincterotomy or unroofing and selected surgical approaches depend on size, symptoms, common-channel and pancreaticobiliary anatomy; confirm an intraduodenal lesion before applying this pathway.",
    "IV": "IVb often follows an extrahepatic-excision framework; IVa additionally requires mapping intrahepatic strictures and disease burden, with selected hepatic resection, drainage strategy or transplant evaluation in specialized care.",
    "V": "Localized Caroli disease may be considered for segmental hepatic resection, whereas diffuse bilateral disease with recurrent cholangitis, portal-hypertension complications or liver failure may prompt transplant evaluation; neither follows automatically from code V.",
    "universal_rule": "Classification informs hepatopancreatobiliary referral and procedural planning but never autonomously orders surgery, endoscopy, transplant or surveillance."
  },
  "malignancy_and_long_term_risk": {
    "pooled_evidence": "The 2018 meta-analysis included 2,904 patients and found 312 malignancies, an overall prevalence of 10.7 percent across heterogeneous retrospective cohorts; do not apply this pooled proportion as an individual prediction.",
    "type_pattern": "Types I and IV accounted for nearly all malignancies and 77 of 78 reported malignant transformations in the type-stratified data. Types II and III were much less represented, so absence of transformation in that small subset is not proof of zero risk.",
    "other_complications": [
      "recurrent_cholangitis",
      "pancreatitis",
      "hepatolithiasis_or_choledocholithiasis",
      "secondary_biliary_cirrhosis",
      "portal_hypertension",
      "anastomotic_or_intrahepatic_stricture_after_treatment"
    ],
    "after_treatment": "Excision reduces but does not eliminate later biliary malignancy and stricture risk; long-term specialist follow-up remains important, particularly for I, IV and V anatomy or residual intrahepatic disease.",
    "communication_rule": "State type, age, prior drainage or excision and suspicious imaging findings; never present a single lifetime percentage as certain for one patient."
  },
  "variant_boundaries": {
    "proposed_type_VI": "Isolated cystic-duct dilatation is a proposed extension, not one of the original five Todani outcome codes. Report isolated cystic-duct cyst and the source convention explicitly.",
    "forme_fruste_and_PBM": "Anomalous pancreaticobiliary maljunction with minimal extrahepatic dilatation may carry important clinical risk but cannot be assigned a Todani type solely from the junction; report PBM and measured duct anatomy separately.",
    "nonordinal_rule": "I through V are anatomic patterns, not sequential severity grades. Type number alone does not rank symptoms, operative complexity or cancer probability."
  },
  "output_contract": [
    "Todani_code_I_to_V",
    "classical_subtype_Ia_Ib_Ic_or_IVa_IVb_when_applicable",
    "explicit_intrahepatic_extrahepatic_and_intraduodenal_distribution",
    "duct_communication_and_pancreaticobiliary_junction",
    "dominant_strictures_stones_and_complications",
    "wall_nodule_mass_or_malignancy_warning",
    "certainty_and_unresolved_differential",
    "prior_intervention_and_residual_anatomy",
    "specialist_planning_context_without_autonomous_management"
  ],
  "missing_input_behavior": [
    "If intrahepatic coverage is incomplete, do not distinguish I from IVa or IVb from IVa; state that the intrahepatic component is unassessed.",
    "If a focal extrahepatic outpouching has unresolved communication or neck anatomy, return I-versus-II uncertainty rather than guessing.",
    "If distal intraduodenal anatomy is not shown, do not assign III from distal duct prominence alone.",
    "If intrahepatic ectasia coexists with uncertain extrahepatic disease, return IVa-versus-V uncertainty and request complete cholangiographic mapping.",
    "If obstruction, inflammation or prior surgery can explain the duct change, withhold congenital classification until the alternative is resolved."
  ],
  "interpretation_limits": [
    "Todani is a morphology and distribution taxonomy, not a diagnostic probability model, malignancy calculator, operative score or surveillance schedule.",
    "The original evidence is surgical and retrospective; several subtypes and proposed extensions have variable usage, and management evidence is not encoded by the Roman numeral alone.",
    "Imaging may not demonstrate the full pancreaticobiliary junction or subtle strictures, and exact anatomy can change after drainage, inflammation or prior reconstruction."
  ],
  "supporting_sources": [
    {
      "role": "primary_classification",
      "citation": "Todani et al. Am J Surg. 1977;134:263-269",
      "doi": "10.1016/0002-9610(77)90359-2",
      "pmid": "889044"
    },
    {
      "role": "anatomic_clarification",
      "citation": "Todani et al. J Hepatobiliary Pancreat Surg. 2003;10:340-344",
      "doi": "10.1007/s00534-002-0733-7"
    },
    {
      "role": "imaging_differential_and_management_review",
      "citation": "Soares et al. J Am Coll Surg. 2014;219:1167-1180",
      "doi": "10.1016/j.jamcollsurg.2014.04.023",
      "pmcid": "PMC4332770"
    },
    {
      "role": "modern_pediatric_management_context",
      "citation": "Jones et al. Transl Gastroenterol Hepatol. 2021;6:37",
      "doi": "10.21037/tgh-20-235",
      "pmcid": "PMC8343510"
    },
    {
      "role": "malignancy_risk_meta_analysis",
      "citation": "ten Hove et al. Br J Surg. 2018;105:482-490",
      "doi": "10.1002/bjs.10798",
      "pmcid": "PMC5900735"
    }
  ],
  "source_locator": "Todani et al. 1977, DOI 10.1016/0002-9610(77)90359-2, pp. 263-269 and classification figure for original types and operative anatomy; Todani et al. 2003, DOI 10.1007/s00534-002-0733-7, pp. 340-344 for Ic and IVa primary-stricture clarification; Soares et al. 2014, PMC4332770, classification, diagnosis, imaging and management sections; ten Hove et al. 2018, PMC5900735, Results and Tables 2-3 for pooled and type-stratified malignancy; Jones et al. 2021, PMC8343510, management and long-term-follow-up sections."
}