Clinical Commander

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id.cellulitis.core.v1

Cellulitis & erysipelas

infectious_diseaseacuteadultacuteinpatientoutpatient
Start encounter →Print handoutPRODUCTION

Necrotizing fasciitis intentionally not covered here — manifest references it as a red-flag exit; separate engine (id.necrotizing-fasciitis.core.v1) planned. PRODUCTION blockers: RxCUI verification + dedicated cellulitis duration test pending. Gap: bite-wound / water-exposure / animal-bite phenotypes share this dossier; consider phenotype-specific axes when manifest splits them. Deepened 2026-05-15 (shard-5-obped-id depth-pass-1, solo wave-7 partial): added co-located _briefs/id.cellulitis.core.v1.md + _research-bundles/id.cellulitis.core.v1.md. Repointed design_brief from the tier3 package path to the in-scope _briefs/ convention. Added 3 severity triggers: cellulitis_progressing_on_appropriate_antibiotics (severe — failure-to-improve at 48-72 h mandates source/pathogen/NF re-evaluation), eron_class_3_or_4_at_presentation (severe — class III-IV mandates inpatient IV regardless of patient preference), cellulitis_in_immunocompromised_host (severe — broader pathogen diversity + lower admission threshold + lower NF threshold). Severity triggers: 6 → 9. Removed 3 misattributed PMIDs (25776532 ProMISe sepsis-EGDT, 29766750 POINT minor-stroke, 23900119 REDUCE-MRSA universal-decolonization) from evidence.pmids — they were inherited copy-paste errors flagged in the shard QUARANTINE. The true Phoenix G STOP trial / Wong LRINEC / IDSA Lipsky-dFI anchors are referenced via primary_guideline text and the research bundle, pending PMID verification in next research:pubmed loop. Phenotype matrix (non-purulent vs purulent vs abscess vs erysipelas × location × host × Eron severity × exposure × antibiotic-history) and Bayesian linkage (LRINEC LRs, DVT-mimic LRs, source-cohort priors, T_treat/T_test/T_surgical thresholds, cross-dossier routing edges) documented in the co-located brief + research bundle; first-class TS fields remain schema-blocked.

Entry points (3)

  • symptom
    Unilateral lower-extremity erythema, warmth, swelling, tenderness (IDSA 2014 SSTI Stevens — classic presentation; NICE 2019 NG141)
    unilateral_erythema_warmth
  • symptom
    Sharply demarcated facial erythema (erysipelas) (NICE 2019 NG141 — raised, well-defined border; IDSA 2014 SSTI Stevens)
    sharp_demarcated_facial_erythema
  • lab_abnormality
    Leukocytosis + clinical skin signs (IDSA 2014 SSTI Stevens — systemic inflammatory response)
    leukocytosis_with_skin_signs

Required inputs (15)

  • temperaturerequired
    vital • used at CONTEXT
    Eron II/III/IV classification; informs IV vs PO and admission threshold (Eron 2003; CREST 2005 — fever drives Eron class upgrade)
  • sbprequired
    vital • used at RED_FLAGS
    Hypotension upgrades to Eron IV / sepsis pathway (Eron 2003 class IV; SSC 2021 — septic shock definition)
  • hrrequired
    vital • used at CONTEXT
    Tachycardia → SIRS / qSOFA element (SSC 2021; IDSA 2014 SSTI Stevens — systemic toxicity marker)
  • pain_out_of_proportionrequired
    symptom • used at RED_FLAGS
    Necrotizing fasciitis red flag — STAT surgical eval (IDSA 2014 SSTI Stevens — cardinal sign of necrotizing infection)
  • crepitus_or_bullaerequired
    symptom • used at RED_FLAGS
    Necrotizing fasciitis or gas gangrene red flag (IDSA 2014 SSTI Stevens — crepitus indicates gas-forming organisms)
  • purulence_drainagerequired
    symptom • used at CONTEXT
    Purulent SSTI → MRSA coverage (IDSA 2014)
  • mrsa_colonization_or_priorrequired
    history • used at CONTEXT
    Drives empiric MRSA coverage (IDSA 2014 SSTI Stevens — purulent SSTI requires anti-MRSA empiric therapy)
  • diabetesrequired
    history • used at CONTEXT
    Polymicrobial coverage threshold; healing trajectory (IDSA 2014 SSTI Stevens; IDSA 2012 diabetic foot — broader empirics)
  • immunocompromiserequired
    history • used at CONTEXT
    Broader empirics + lower admission threshold (IDSA 2014 SSTI Stevens — immunocompromised host requires Eron class upgrade; NICE 2019 NG141)
  • tinea_pedis_or_lymphedema
    history • used at FOLLOWUP
    Modifiable risk factor for recurrence (NICE 2019 NG141); PATCH II prophylaxis candidacy (Thomas NEJM 2013 PATCH II)
  • wbcrequired
    lab • used at INITIAL_WORKUP
    SIRS criterion + severity tracking (IDSA 2014 SSTI Stevens — baseline CBC for systemic assessment)
  • crp
    lab • used at INITIAL_WORKUP
    Trend for response to therapy (NICE 2019 NG141 — serial CRP guides IV-to-PO switch and duration)
  • creatininerequired
    lab • used at TREATMENT
    Cefazolin / vancomycin renal dosing (IDSA 2014 SSTI Stevens — dose adjustment; IDSA 2020 vancomycin consensus — AUC-based dosing)
  • lactate
    lab • used at INITIAL_WORKUP
    Sepsis bundle when SIRS + skin source (SSC 2021 — lactate-guided resuscitation in SSTI sepsis)
  • doppler_ultrasound
    imaging • used at BRANCHING_WORKUP
    Rule out DVT mimic; abscess / fluid collection (NICE 2019 NG141 — unilateral leg swelling differential; IDSA 2014 SSTI Stevens — bedside US for abscess)

12-phase flow (12)

  1. 1FRAME
    Non-purulent vs purulent cellulitis (IDSA 2014 SSTI Stevens — distinct empiric pathways); exclude necrotizing fasciitis (separate engine) and erysipelas variant (NICE 2019 NG141)
    advance: scope confirmed
  2. 2ENTRY
    Recognise classic skin signs; capture symptom timing (NICE 2019 NG141 — clinical diagnosis; IDSA 2014 SSTI Stevens — symptom onset guides acuity)
    advance: entry trigger present
  3. 3CONTEXT
    Eron class drivers — fever, comorbidities, immunocompromise, MRSA risk, water/animal exposure (Eron 2003 classification; IDSA 2014 SSTI Stevens — exposure history determines empiric spectrum)
    inputs: temperature, hr, purulence_drainage, mrsa_colonization_or_prior, diabetes, immunocompromise
    advance: risk + Eron class assigned
  4. 4RED_FLAGS
    Pain out of proportion, crepitus, bullae, rapid spread, systemic toxicity → STAT surgical / ICU (IDSA 2014 SSTI Stevens — necrotizing fasciitis red-flag screen; SSC 2021 — qSOFA for sepsis screening)
    inputs: pain_out_of_proportion, crepitus_or_bullae, sbp
    actions: calc.qsofa
    advance: red flags ruled out or routed
  5. 5INITIAL_WORKUP
    CBC, BMP, CRP, blood cultures if Eron III/IV or systemic (IDSA 2014 SSTI Stevens), wound culture if purulent / abscess drained (IDSA 2014 SSTI Stevens)
    inputs: wbc, crp, creatinine
    actions: panel.cbc, panel.renal, panel.inflammation
    advance: workup sent; mark area for spread (CREST 2005 — border tracing at presentation)
  6. 6BRANCHING_WORKUP
    Doppler if DVT considered (NICE 2019 NG141); bedside US for abscess (IDSA 2014 SSTI Stevens); MRI/CT only if necrotizing suspected — do NOT delay surgery (IDSA 2014 SSTI Stevens)
    actions: workup.le_edema
    advance: mimics excluded
  7. 7DIFFERENTIAL
    DVT, stasis dermatitis, contact dermatitis, gout, septic arthritis, necrotizing fasciitis, lymphedema, erysipeloid, erythema migrans (NICE 2019 NG141 — common mimics of cellulitis; IDSA 2014 SSTI Stevens — misdiagnosis rate 30%)
    advance: mimics excluded
  8. 8RISK_STRATIFICATION
    Eron I-IV → outpatient PO vs inpatient IV vs ICU (Eron 2003 classification; CREST 2005 — Eron-based disposition algorithm)
    inputs: temperature, sbp
    advance: Eron class + disposition pre-set
  9. 9TREATMENT
    Non-purulent: cephalexin / cefazolin (IDSA 2014 SSTI Stevens) or flucloxacillin in UK (NICE 2019 NG141); purulent + MRSA risk: TMP-SMX / doxycycline / clindamycin PO or vancomycin IV (IDSA 2014 SSTI Stevens); add anaerobic coverage for diabetic / bite / water exposure (IDSA 2014 SSTI Stevens); duration 5-7 days if improving by day 5 (Phoenix G NEJM 2023 STOP trial); elevate limb, treat tinea/lymphedema drivers (NICE 2019 NG141; CREST 2005)
    inputs: creatinine
    advance: antibiotic + adjunct therapy started, follow-up in 48-72h booked (NICE 2019 NG141)
  10. 10DISPOSITION
    Eron I → outpatient; Eron II → outpatient + 24-48h reassess; Eron III → admit IV; Eron IV → ICU + surgical consult (Eron 2003 classification; CREST 2005; NICE 2019 NG141)
    inputs: temperature, sbp
    advance: disposition documented
  11. 11MONITORING
    Border tracing 24-48h (CREST 2005; NICE 2019 NG141); CRP / WBC trend (IDSA 2014 SSTI Stevens); transition IV→PO when afebrile + improving 48h (NICE 2019 NG141 — IV-to-PO switch criteria)
    inputs: wbc, crp
    actions: panel.inflammation
    advance: response confirmed at 48-72h (IDSA 2014 SSTI Stevens)
  12. 12FOLLOWUP
    Treat tinea pedis / lymphedema / venous insufficiency (NICE 2019 NG141 — modifiable risk factors); PATCH II prophylactic penicillin V if ≥2 episodes/year (Thomas NEJM 2013 PATCH II); counsel on early re-presentation (NICE 2019 NG141)
    advance: recurrence-prevention plan documented