Use the complete six-stage Kaiser CT modification, preserve CT-versus-operative truth and clinical physiology, and never import WSES numbering or a management-size threshold into the stage silently.
{
"categories": [
{
"outcome_code": "0",
"state": "clinically_mild_diverticulitis",
"CT": "diverticula_with_or_without_colonic_wall_thickening",
"abscess": "absent",
"generalized_peritonitis": "absent"
},
{
"outcome_code": "Ia",
"state": "confined_pericolic_inflammation_or_phlegmon",
"CT": "wall_thickening_with_inflammatory_reaction_in_pericolic_fat",
"abscess": "absent",
"generalized_peritonitis": "absent"
},
{
"outcome_code": "Ib",
"state": "confined_pericolic_or_mesocolic_abscess",
"CT": "stage_Ia_changes_plus_abscess_near_primary_process",
"historical_size_descriptor": "less_than_5_cm",
"generalized_peritonitis": "absent"
},
{
"outcome_code": "II",
"state": "distant_abscess",
"CT": "pelvic_interloop_intra_abdominal_or_retroperitoneal_abscess_distant_from_primary_process",
"generalized_peritonitis": "absent"
},
{
"outcome_code": "III",
"state": "generalized_purulent_peritonitis",
"CT": "free_air_with_local_or_generalized_free_fluid_and_possible_peritoneal_thickening_without_open_bowel_communication",
"contamination": "purulent_not_fecal"
},
{
"outcome_code": "IV",
"state": "generalized_fecal_peritonitis",
"CT": "free_perforation_with_open_communication_to_bowel_lumen",
"contamination": "gross_fecal"
}
],
"classification_identity_and_scope": {
"intended_use": "Describe the anatomic extent of acute colonic diverticulitis using the six-stage Kaiser 2005 CT modification of Hinchey.",
"naming_rule": "Return Kaiser modified Hinchey plus the stage. Do not call an unlabeled WSES, Neff, Ambrosetti, Sallinen or original operative Hinchey category simply Hinchey.",
"classification_unit": "one_acute_episode_at_one_defined_timepoint",
"outside_scope": [
"diagnosis_from_symptoms_alone",
"sepsis_or_organ_failure_grade",
"fistula_or_stricture_classification",
"colon_cancer_exclusion",
"universal_treatment_algorithm",
"calibrated_individual_mortality_or_recurrence_probability"
]
},
"required_inputs_and_provenance": {
"imaging": [
"contrast_enhanced_abdominopelvic_CT_when_clinically_appropriate",
"affected_colonic_segment",
"wall_thickening",
"pericolic_fat_inflammation",
"extraluminal_gas_location",
"fluid_or_abscess_location_and_maximum_diameter_cm",
"free_fluid_distribution",
"open_bowel_communication_or_fecal_contamination_if_known"
],
"clinical": [
"examination_for_local_or_generalized_peritonitis",
"hemodynamics",
"sepsis_and_organ_dysfunction",
"immune_status",
"frailty_and_comorbidity",
"response_to_initial_management"
],
"timing": "State CT and examination times and whether antibiotics, drainage or surgery preceded them; a treated or evolving episode can change stage.",
"technical_gate": "If CT quality or contrast timing cannot distinguish an enhancing collection from phlegmon or map distant gas/fluid, retain the unresolved adjacent categories and recommend clinical correlation rather than forcing a stage."
},
"grading_algorithm": [
{
"priority": 1,
"if": "generalized_fecal_peritonitis_or_free_perforation_with_open_bowel_lumen_communication",
"output_code": "IV"
},
{
"priority": 2,
"if": "generalized_purulent_peritonitis_without_gross_fecal_contamination",
"output_code": "III"
},
{
"priority": 3,
"if": "pelvic_interloop_intra_abdominal_or_retroperitoneal_abscess_distant_from_primary_process",
"output_code": "II"
},
{
"priority": 4,
"if": "confined_pericolic_or_mesocolic_abscess_near_primary_process",
"output_code": "Ib"
},
{
"priority": 5,
"if": "confined_pericolic_inflammation_or_phlegmon_without_abscess",
"output_code": "Ia"
},
{
"priority": 6,
"if": "clinically_mild_episode_with_diverticula_with_or_without_wall_thickening_and_no_more_advanced_feature",
"output_code": "0"
}
],
"boundary_rules": {
"stage_0_Ia": "Stage 0 is the historical clinically mild category with diverticula with or without wall thickening. Definite pericolic inflammatory reaction or phlegmon supports Ia. Do not equate asymptomatic diverticulosis with stage 0.",
"stage_Ia_Ib": "A phlegmon is inflammatory tissue without a drainable fluid collection; an unequivocal pericolic or mesocolic abscess supports Ib. Record rim enhancement, gas, dimensions and drainable access separately.",
"stage_Ib_II": "Kaiser descriptions place a nearby abscess under 5 cm in Ib and a pelvic, interloop, intra-abdominal or retroperitoneal abscess distant from the primary process in II. Location is central; an unusually large but still pericolic collection exposes a scheme ambiguity and must not be silently reclassified from a management-size threshold.",
"stage_II_III": "A distant but contained abscess is II. Diffuse purulent peritonitis is III and requires clinical or operative evidence; free fluid or distant gas alone is not proof of generalized purulent peritonitis.",
"stage_III_IV": "Purulent contamination without open bowel communication is III; gross fecal contamination or demonstrated open communication is IV. CT may not reliably make this distinction, so return III-versus-IV suspected when operative or clinical evidence is absent.",
"free_air_rule": "Contained pericolic gas or even distant free gas is not automatically fecal peritonitis. Report gas distance, volume, free fluid and peritoneal signs and keep the named classification rules visible."
},
"CT_and_operative_truth_boundary": {
"original_Hinchey": "The 1978 system was an operative classification of perforated disease with stages I-IV; it did not contain 0, Ia or Ib.",
"Kaiser_modification": "The 2005 CT modification adds stage 0 and splits stage I into Ia and Ib, enabling preoperative description but not making CT infallible for peritoneal contamination.",
"escalation_rule": "When operative findings demonstrate purulent or fecal peritonitis, preserve both the preoperative CT impression and the operative stage rather than rewriting one as if it had always been known."
},
"WSES_noninterchangeability": {
"WSES_0": "Uncomplicated diverticulitis with diverticula, wall thickening and pericolic fat densification.",
"WSES_1A": "Pericolic air bubbles or a small amount of pericolic fluid without abscess, within 5 cm of the inflamed segment.",
"WSES_1B": "Abscess no greater than 4 cm.",
"WSES_2A": "Abscess greater than 4 cm.",
"WSES_2B": "Distant gas more than 5 cm from the inflamed segment.",
"WSES_3": "Diffuse fluid without distant free gas.",
"WSES_4": "Diffuse fluid with distant free gas.",
"translation_guard": "WSES numbers encode different CT features and thresholds. Do not translate WSES 1A/1B/2A/2B/3/4 one-to-one into Kaiser modified Hinchey Ia/Ib/II/III/IV."
},
"current_management_context": {
"universal_rule": "Management follows physiology, sepsis, immune status, abscess size and access, clinical trajectory, local expertise and patient goals; the modified Hinchey label is context, not an autonomous order.",
"stage_0_and_selected_Ia": "For low-risk, immunocompetent patients with mild uncomplicated disease and reliable follow-up, current ACG guidance suggests against routine antibiotics. Antibiotics remain appropriate with high-risk features, immunocompromise, frailty, systemic inflammation, vomiting, unreliable follow-up or complicated findings; pericolic extraluminal gas is handled separately in WSES guidance.",
"stages_Ib_and_II": "Treat a diverticular abscess with antibiotics and source-control planning. WSES uses under 4-5 cm as a reasonable antibiotics-alone trial threshold and drainage plus antibiotics for larger collections when feasible; ASCRS usually recommends image-guided drainage for stable patients with abscesses over 3 cm. Preserve this guideline difference rather than inventing one universal cutoff.",
"drainage_failure": "If drainage is not feasible, selected stable patients may receive antibiotics with close monitoring; worsening inflammatory signs, persistent abscess, sepsis or failed nonoperative care requires urgent surgical reassessment.",
"stages_III_and_IV": "Generalized peritonitis requires urgent resuscitation, antibiotics and operative source control. WSES favors Hartmann resection for critically ill patients or those with major comorbidity and permits primary resection with anastomosis with or without diversion in selected stable patients. Laparoscopic lavage is not first-line and is reserved for selected purulent-peritonitis cases.",
"elective_surgery": "Stage II or a successfully treated abscess does not automatically mandate interval colectomy. Current ACG/AGA practice emphasizes personalized colorectal-surgical discussion based on severity, recurrences, immune status, quality of life, operative risk and patient preferences.",
"colon_evaluation": "Follow-up colon evaluation depends on prior high-quality colonoscopy, complicated versus uncomplicated disease, alarm features and clinical course; a modified Hinchey stage does not itself exclude malignancy."
},
"risk_evidence_and_limits": {
"direction": "Abscess, distant spread and generalized peritonitis indicate increasing anatomic complexity, but the categories do not provide validated universal per-stage mortality or failure probabilities.",
"Kaiser_historical_cohort": "In the 511-patient retrospective Kaiser cohort, 22.2 percent of patients with an abscess required urgent resection; recurrence was 13 percent for mild cases and 41.2 percent for conservatively treated pelvic abscesses. These are historical center-level observations, not current individual predictions.",
"small_abscess_synthesis": "WSES cites an observational pooled failure rate of about 20 percent and mortality of 0.6 percent for systemically treated limited-size abscesses. This applies to selected cohorts and does not attach automatically to every Ib or II lesion.",
"dominant_predictors": "Hemodynamic instability, sepsis and organ dysfunction, immune compromise, frailty, abscess accessibility, diffuse contamination and response to therapy can outweigh the ordinal label."
},
"required_companion_report": [
"affected_colonic_segment_and_extent",
"wall_thickening_and_pericolic_inflammation",
"extraluminal_gas_location_and_distance",
"abscess_count_location_three_dimensions_and_drainage_window",
"free_fluid_distribution_and_peritoneal_thickening",
"suspected_open_bowel_communication_or_fecal_contamination",
"obstruction_fistula_stricture_or_possible_malignancy",
"clinical_peritonitis_hemodynamics_sepsis_organ_dysfunction_and_immune_status",
"named_classification_and_any_CT_operational_threshold"
],
"missing_input_behavior": [
"If there is no CT and the episode is not already characterized operatively, do not manufacture a CT-modified Hinchey stage from symptoms alone.",
"If phlegmon versus abscess is unresolved, return Ia-versus-Ib and preserve collection morphology and technical limitation.",
"If abscess location and size point to conflicting or unspecified implementations, report both and label the scheme ambiguity rather than mapping a treatment cutoff into a stage.",
"If generalized peritonitis is clinically suspected but purulent versus fecal contamination is unknown, return III-versus-IV suspected pending source control.",
"If a WSES stage is supplied, retain it as WSES and do not silently convert it to modified Hinchey."
],
"agent_output_contract": [
"Kaiser_modified_Hinchey_0_Ia_Ib_II_III_IV_or_explicit_uncertainty",
"CT_and_clinical_assessment_timepoints",
"raw_anatomic_features_and_abscess_measurements",
"operative_findings_when_available",
"sepsis_hemodynamics_immune_status_and_clinical_trajectory",
"named_guideline_when_discussing_abscess_thresholds",
"no_WSES_translation_treatment_order_or_numeric_prognosis_from_stage_alone"
],
"supporting_sources": [
{
"role": "original_operative_classification",
"citation": "Hinchey et al. Adv Surg. 1978;12:85-109",
"pmid": "735943"
},
{
"role": "Kaiser_CT_modification_and_cohort",
"citation": "Kaiser et al. Am J Gastroenterol. 2005;100:910-917",
"doi": "10.1111/j.1572-0241.2005.41154.x",
"pmid": "15784040"
},
{
"role": "open_CT_stage_table",
"citation": "Tiralongo et al. Diagnostics. 2023;13:3628",
"doi": "10.3390/diagnostics13243628",
"pmcid": "PMC10742435"
},
{
"role": "emergency_and_abscess_guidance",
"citation": "Sartelli et al. World J Emerg Surg. 2020;15:32",
"doi": "10.1186/s13017-020-00313-4",
"pmcid": "PMC7206757"
},
{
"role": "colorectal_surgery_guidance",
"citation": "Hall et al. Dis Colon Rectum. 2020;63:728-747",
"doi": "10.1097/DCR.0000000000001679"
},
{
"role": "current_outpatient_guidance",
"citation": "Peery et al. Am J Gastroenterol. 2026;121:1549-1561",
"doi": "10.14309/ajg.0000000000004047",
"pmid": "42390126"
},
{
"role": "personalized_elective_management",
"citation": "Peery et al. Gastroenterology. 2021;160:906-911.e1",
"doi": "10.1053/j.gastro.2020.09.059",
"pmcid": "PMC7878331"
}
],
"source_locator": "Kaiser et al. 2005, PMID 15784040, abstract and modified-stage analysis; Tiralongo et al. 2023, PMC10742435, Hinchey section and classification table for all six CT categories; Sartelli et al. 2020, PMC7206757, classification, pericolic gas, abscess, peritonitis and operative recommendations; Hall et al. 2020 ASCRS guideline abscess and elective-surgery recommendations; Peery et al. 2026 ACG recommendations for low-risk uncomplicated disease and current outpatient care; Peery et al. 2021 AGA best-practice advice for personalized resection."
}