12-phase flow (12)

1. 1FRAME
   Frame as ACUTE rhinosinusitis (<4 wk) and set the two decisive questions: (1) viral ARS vs ABRS by symptom duration/trajectory (>90-98% of ARS is viral; ~0.5-2% of viral URI becomes ABRS — Payne AAO-HNS 2025; Chow IDSA 2012); (2) uncomplicated vs complicated (orbital/intracranial emergency). Chronic rhinosinusitis (≥12 wk) and headache/dental mimics are differentiated, not re-managed; complications are recognised then routed OUT by engine_id.
   advance: ARS scope confirmed; CRS and complication/mimic pathways routed by engine_id, not re-authored
2. 2ENTRY
   Recognise the entry pattern: cardinal symptom cluster (obstruction + purulent discharge + facial pain/pressure), persistent ≥10 d without improvement, double-sickening, or severe onset; OR an orbital/neurologic red-flag presentation. Capture symptom duration and trajectory up front — these drive everything downstream.
   inputs: symptom_duration_days, symptom_trajectory_pattern
   advance: entry pattern identified; duration + trajectory recorded
3. 3CONTEXT
   Build the viral-vs-ABRS prior: purulence, facial-pain location/laterality/character, fever height and duration, age band, and the URI background. Three ABRS patterns formalised — persistent (≥10 d no improvement), worsening/double-sickening, severe-onset (≥39 °C + purulence ≥3-4 d). This phase sets the pretest probability used at DIFFERENTIAL.
   inputs: purulent_nasal_discharge, facial_pain_pressure_location, temperature, age_band
   actions: calc.centor
   advance: ABRS pattern (or viral-ARS pattern) and pretest prior assigned
4. 4RED_FLAGS
   Screen the EMERGENCIES that change everything: orbital (proptosis, ophthalmoplegia, diplopia, reduced acuity/colour vision, RAPD → orbital cellulitis/subperiosteal abscess) → route OUT to ophtho.orbital-cellulitis.core.v1; intracranial (severe/worsening headache, meningism, vomiting, seizure, altered mentation, focal deficit, Pott's puffy forehead swelling, cavernous-sinus signs) → route OUT to neuro.bacterial-meningitis.core.v1; systemic toxicity / qSOFA≥2 → route OUT to id.sepsis.core.v1; immunocompromise/DKA + facial pain/eschar → acute invasive fungal rhinosinusitis (emergent ENT + biopsy + antifungal). These are recognised and routed here, NOT managed here.
   inputs: orbital_warning_signs, intracranial_warning_signs, immunocompromise_or_uncontrolled_diabetes
   actions: calc.qsofa, calc.news2, workup.acute_red_eye, workup.bacterial_meningitis
   advance: orbital + intracranial + sepsis + invasive-fungal red flags screened and routed by engine_id if positive
5. 5INITIAL_WORKUP
   Acute rhinosinusitis is a CLINICAL diagnosis — do NOT image uncomplicated ARS (Payne AAO-HNS 2025 strong recommendation against; Wald AAP 2013). Anterior rhinoscopy / endoscopy if available. Bloodwork is NOT routine for uncomplicated ARS; reserve CBC/CRP/CMP for the systemically unwell, the complicated, the immunocompromised, or when an alternative diagnosis is in play (sepsis/complication workup).
   inputs: temperature
   actions: panel.cbc, panel.inflammation
   advance: clinical diagnosis made; imaging deliberately withheld unless complication/alternative suspected
6. 6BRANCHING_WORKUP
   Branch on red-flag presence. Complication suspected → contrast CT sinuses/orbits/brain + urgent ENT/ophthalmology/neurosurgery (route OUT). Headache-dominant without purulence/obstruction → headache workup, pivot to migraine/tension-type. Maxillary unilateral pain + dental trigger → odontogenic source (dental imaging/referral). Immunocompromised + facial/orbital findings → emergent invasive-fungal pathway (nasal endoscopy + biopsy, do not delay). Uncomplicated → no further workup, proceed to the watchful-waiting-vs-antibiotic decision.
   inputs: contrast_ct_sinuses_orbits_brain
   actions: workup.acute_headache, workup.anosmia
   advance: complication imaged + routed, OR alternative source assigned, OR uncomplicated ARS confirmed
7. 7DIFFERENTIAL
   Terminal ARS differential with explicit pivots: viral ARS (<10 d, improving, no double-sickening — pivot: trajectory) vs ABRS (≥10 d no improvement OR double-sickening OR severe onset — pivot: duration/trajectory + purulence + fever) vs migraine ("sinus headache" — pivot: unilateral throbbing + photophobia/phonophobia + aura + no purulence; route to neuro.migraine.core.v1) vs tension-type headache (bilateral band, no nasal signs) vs odontogenic/dental sinusitis (maxillary, percussion-tender tooth, unilateral foul discharge — pivot: dental source) vs acute invasive fungal rhinosinusitis (immunocompromised/DKA + necrotic eschar/anaesthetic mucosa + orbital/CNS findings — pivot: host + necrosis) vs CRS (≥12 wk — pivot: duration) vs neoplasm (unilateral, epistaxis, cheek numbness, refractory).
   inputs: unilateral_facial_features_for_mimic_split
   advance: single best diagnosis selected; mimic vs ABRS pivot finding documented
8. 8RISK_STRATIFICATION
   For confirmed ABRS, stratify: uncomplicated (outpatient, watchful-waiting eligible) vs complicated (orbital/intracranial — inpatient/ED, route OUT) vs resistance-risk (recent antibiotics, age <2/>65, immunocompromise, severe illness, prior hospitalisation — high-dose amox-clav). Systemic-toxicity overlay (qSOFA/NEWS2) and special-population modifiers (pregnancy, pediatric, renal) are layered here.
   inputs: recent_antibiotic_use_or_resistance_risk, temperature
   actions: calc.qsofa, calc.news2
   advance: ABRS severity tier + resistance-risk + special-population overlay assigned
9. 9TREATMENT
   Uncomplicated ABRS — SHARED-DECISION watchful waiting (symptomatic care, NO antibiotic, with a safety-net for follow-up if not improving by 7 d or worsening) OR initial antibiotic; 2025 AAO-HNS extends watchful waiting to ALL uncomplicated ABRS regardless of severity. If treating: amoxicillin ± clavulanate first-line (high-dose amox-clav if resistance risk); penicillin allergy → doxycycline or a respiratory fluoroquinolone (levofloxacin/moxifloxacin — reserve, tendon/QT/CNS risk). Adjuncts for symptom relief (viral AND ABRS): intranasal corticosteroid, saline irrigation, analgesia/antipyretic — NOT antibiotics for viral ARS. Pediatric: amoxicillin ± clavulanate, observe-3-days option for persistent. Complicated → IV broad-spectrum + emergent ENT/ophtho/neurosurgery (route OUT). Pregnancy: amox ± clav preferred, avoid doxycycline/fluoroquinolone.
   inputs: penicillin_allergy, recent_antibiotic_use_or_resistance_risk, pregnancy_lactation_status, creatinine
   advance: watchful-waiting vs antibiotic decision made via shared decision-making; adjuncts started; safety-net follow-up booked
10. 10DISPOSITION
    Uncomplicated viral ARS / uncomplicated ABRS → discharge with symptomatic care ± delayed/immediate prescription and a 7-day safety-net. Complicated (orbital/intracranial), systemic toxicity, or suspected invasive fungal disease → admit and route OUT (ophtho.orbital-cellulitis.core.v1 / neuro.bacterial-meningitis.core.v1 / id.sepsis.core.v1). Treatment failure at the reassessment point → re-confirm ABRS, exclude complication/alternative, escalate antibiotic.
    inputs: temperature, orbital_warning_signs
    advance: disposition documented; complications/toxicity admitted and routed out
11. 11MONITORING
    Reassess at 7 days from diagnosis (Payne AAO-HNS 2025) — or sooner / within 72 h if worsening (Wald AAP 2013): confirm ABRS, exclude an evolving complication or alternative diagnosis, and detect treatment failure. Counsel that most viral ARS resolves within ~10-14 days and ~46% of ARS is cured by 1 wk / ~64% by 14 d WITHOUT antibiotics (Lemiengre Cochrane 2018). Worsening orbital/neurologic signs at any time → immediate contrast CT + route OUT.
    inputs: temperature, orbital_warning_signs
    actions: panel.inflammation
    advance: improvement confirmed at 7 d, OR failure/complication triggers re-evaluation and escalation/route-out
12. 12FOLLOWUP
    Educate on natural history (viral ARS self-limited; antibiotic NNT ~11-15, NNH ~8 for adverse effects — Lemiengre Cochrane 2018; Young Lancet 2008) and antibiotic stewardship. Define recurrence (≥4 ABRS episodes/yr with symptom-free intervals) and the CRS boundary (symptoms ≥12 wk with objective sinonasal inflammation → CRS pathway / ENT referral). Return precautions: orbital swelling, visual change, severe/worsening headache, neck stiffness, altered mentation → emergency re-presentation. ENT referral for recurrent ARS, complications, anatomic factors, immunodeficiency, or chronic transition.
    inputs: symptom_duration_days
    actions: workup.lymphadenopathy
    advance: natural-history + stewardship counselling done; recurrence/CRS boundary defined; ENT referral made if criteria met