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derm.skin-abscess.core.v1

Cutaneous abscess / furuncle / carbuncle (I&D-primary purulent SSTI)

dermatologyacuteadultpediatricacuteoutpatient
Start encounter →Print handoutPRODUCTION

Shard-06 Phase C gap-fill (2026-05-17): new I&D-primary purulent-SSTI / abscess dossier. Distinct from id.cellulitis.core.v1 (non-purulent) — the purulent-vs-non-purulent IDSA pivot is encoded in sibling_differentiation[0]. Master discriminator is source control (incision & drainage), not antibiotic selection: a simple drained abscess in a healthy host is cured by the procedure (Schmitz Ann Emerg Med 2010 PMID 20346539). Adjunctive TMP-SMX/clindamycin add NNT-quantified cure benefit at/above the small-abscess severity threshold (Talan NEJM 2016 PMID 26962903 +6.9%; Daum NEJM 2017 PMID 28657870 +13–14%). RxCUIs live-reverse-verified against RxNav 2026-05-22 (cui→properties name match): clindamycin 2582, doxycycline 3640, cephalexin 2231, vancomycin 11124, rifampin 9384 confirmed. THREE codes were corrected this pass: TMP-SMX 10180 (resolved to single-ingredient "sulfamethoxazole" only) → 10831 (MIN "sulfamethoxazole / trimethoprim", the fixed-dose combination); mupirocin 30144 (RxNav returned EMPTY/invalid) → 42372 (IN mupirocin); chlorhexidine 2364 (RxNav returned EMPTY/invalid) → 2358 (IN chlorhexidine). All replacements reverse-verified. Missing rxcui does not block INTEGRATED. Sibling routing edges: id.necrotising-fasciitis.core.v1 (necrotizing red flags — do NOT bedside-incise), id.sepsis.core.v1 (qSOFA ≥2 + skin source → SSC Hour-1 bundle), id.cellulitis.core.v1 (non-purulent pivot), derm.epidermoid-cyst.core.v1 + derm.hidradenitis-suppurativa.chronic.v1 (planned siblings; recurrent-intertriginous-abscess HS phenotype). HS/epidermoid-cyst engine_ids are forward references (engines not yet built) used only in sibling_differentiation strings — they are not registry tool ids and do not affect the audit. INTEGRATED blockers toward PRODUCTION: live RxNav rxcui verification, terminology pipeline validation (ICD-10/SNOMED/LOINC per project_terminology_pipeline_status.md ⚠ partial), and a dedicated abscess-pathway test beyond the shared contract test.

Entry points (5)

  • symptom
    Fluctuant, tender, erythematous nodule ± pointing/spontaneous drainage — cutaneous abscess (IDSA 2014 SSTI Stevens PMID 24973422 — purulent SSTI)
    fluctuant_tender_erythematous_nodule
  • symptom
    Tender perifollicular pustule/nodule (furuncle) or coalesced multi-loculated mass with multiple draining sinuses (carbuncle) in hair-bearing skin (IDSA 2014 SSTI Stevens PMID 24973422)
    furuncle_or_carbuncle_hair_bearing
  • symptom
    Recurrent painful nodules/abscesses with sinus tracts/scarring in axilla/groin/inframammary — recurrent furunculosis vs hidradenitis suppurativa pivot (Alikhan JAAD 2019 PMID 30872156)
    recurrent_abscesses_intertriginous
  • symptom
    Abscess with fever/tachycardia/hypotension or rapidly spreading erythema — sepsis vs necrotizing screen before drainage (SSC 2026; IDSA 2014 SSTI Stevens PMID 24973422)
    abscess_with_systemic_features
  • history
    Injection-site abscess in person who injects drugs — high MRSA + polymicrobial/anaerobic + occult deep extension risk (IDSA 2014 SSTI Stevens PMID 24973422)
    iv_drug_use_injection_site_abscess

Required inputs (18)

  • fluctuancerequired
    symptom • used at CONTEXT
    Fluctuance is the cardinal sign that a collection is drainable — drives the I&D-vs-observe decision (IDSA 2014 SSTI Stevens PMID 24973422 — incision & drainage is primary therapy for abscess)
  • abscess_diameter_cmrequired
    symptom • used at RISK_STRATIFICATION
    Diameter >2 cm is a key adjunctive-antibiotic and disposition discriminator (Talan NEJM 2016 PMID 26962903; IDSA 2014 SSTI Stevens PMID 24973422)
  • surrounding_cellulitis_extentrequired
    symptom • used at RISK_STRATIFICATION
    Surrounding cellulitis upgrades severity and triggers adjunctive systemic antibiotics after I&D (IDSA 2014 SSTI Stevens PMID 24973422)
  • pain_out_of_proportionrequired
    symptom • used at RED_FLAGS
    Pain out of proportion, dusky skin, crepitus, bullae → necrotizing fasciitis red flag — do NOT incise at bedside; emergent surgery (IDSA 2014 SSTI Stevens PMID 24973422)
  • anatomic_danger_zonerequired
    symptom • used at RED_FLAGS
    Facial danger triangle / perirectal / perineal / hand / deep-space location changes procedure setting (specialist/OR) and risk (IDSA 2014 SSTI Stevens PMID 24973422)
  • temperaturerequired
    vital • used at CONTEXT
    Fever drives severity class (moderate→severe purulent SSTI) and adjunctive-antibiotic decision (IDSA 2014 SSTI Stevens PMID 24973422)
  • sbprequired
    vital • used at RED_FLAGS
    Hypotension → sepsis pathway, route to id.sepsis.core.v1 SSC Hour-1 bundle (SSC 2026)
  • hrrequired
    vital • used at CONTEXT
    Tachycardia is a qSOFA/SIRS element when systemic toxicity present (SSC 2026)
  • recurrent_abscess_count
    history • used at FOLLOWUP
    ≥2 episodes/year defines recurrent furunculosis → decolonization candidacy and HS reconsideration (Fritz CID 2012 PMID 22198793; Alikhan JAAD 2019 PMID 30872156)
  • mrsa_colonization_or_priorrequired
    history • used at CONTEXT
    Prior MRSA / household MRSA drives adjunctive agent choice and decolonization (Moran NEJM 2006 PMID 16914702; Fritz CID 2012 PMID 22198793)
  • diabetesrequired
    history • used at CONTEXT
    Diabetes lowers the threshold for adjunctive antibiotics and admission; impaired healing (IDSA 2014 SSTI Stevens PMID 24973422)
  • immunocompromiserequired
    history • used at CONTEXT
    Neutropenia / transplant / biologic / advanced HIV → adjunctive antibiotics after I&D, lower admission threshold, broader pathogens (IDSA 2014 SSTI Stevens PMID 24973422)
  • injection_drug_use
    history • used at CONTEXT
    PWID injection-site abscess: high polymicrobial/anaerobic + occult deep extension; consider US + broader coverage (IDSA 2014 SSTI Stevens PMID 24973422)
  • pregnancy
    history • used at TREATMENT
    Antibiotic safety: avoid TMP-SMX (1st trimester / near term), tetracyclines; clindamycin pregnancy-acceptable (IDSA 2014 SSTI Stevens PMID 24973422)
  • wbc
    lab • used at INITIAL_WORKUP
    Leukocytosis supports systemic involvement / severe purulent SSTI class (IDSA 2014 SSTI Stevens PMID 24973422)
  • crp
    lab • used at INITIAL_WORKUP
    CRP/PCT supports severity assessment and response trend when systemic features present (IDSA 2014 SSTI Stevens PMID 24973422)
  • creatinine
    lab • used at TREATMENT
    TMP-SMX and vancomycin renal dose adjustment; baseline before TMP-SMX (hyperkalemia/AKI risk) (IDSA 2014 SSTI Stevens PMID 24973422)
  • point_of_care_ultrasound
    imaging • used at BRANCHING_WORKUP
    POCUS distinguishes drainable abscess from cellulitis when exam equivocal; finds occult/deep collections (Subramaniam Acad Emerg Med 2016 PMID 27770490)

12-phase flow (12)

  1. 1FRAME
    Purulent vs non-purulent SSTI pivot (IDSA 2014 SSTI Stevens PMID 24973422 — distinct pathways); abscess/furuncle/carbuncle → I&D-primary; exclude necrotizing fasciitis (id.necrotising-fasciitis.core.v1) and non-purulent cellulitis (id.cellulitis.core.v1)
    advance: purulent collection confirmed and scope set
  2. 2ENTRY
    Recognise fluctuant tender nodule / furuncle / carbuncle; capture onset, recurrence, anatomic site (IDSA 2014 SSTI Stevens PMID 24973422)
    advance: entry trigger present
  3. 3CONTEXT
    Severity drivers — fluctuance, fever, tachycardia, size, MRSA risk, diabetes, immunocompromise, PWID, recurrence (IDSA 2014 SSTI Stevens PMID 24973422; Moran NEJM 2006 PMID 16914702)
    inputs: fluctuance, temperature, hr, mrsa_colonization_or_prior, diabetes, immunocompromise
    advance: purulent-SSTI severity class (mild/moderate/severe) assigned
  4. 4RED_FLAGS
    Necrotizing fasciitis screen (pain out of proportion, dusky/bullae/crepitus, rapid spread) — do NOT bedside-drain, emergent surgery; sepsis screen (qSOFA); danger-zone anatomy (facial triangle/perirectal/hand/deep) (IDSA 2014 SSTI Stevens PMID 24973422; SSC 2026)
    inputs: pain_out_of_proportion, anatomic_danger_zone, sbp
    actions: calc.qsofa, calc.sirs
    advance: necrotizing + sepsis ruled out or routed to surgical/sepsis engine
  5. 5INITIAL_WORKUP
    Clinical diagnosis; wound culture of purulent material at I&D if moderate/severe, recurrent, immunocompromised, treatment failure, or outbreak (IDSA 2014 SSTI Stevens PMID 24973422); CBC + inflammation + blood cultures only if systemic toxicity (IDSA 2014 SSTI Stevens PMID 24973422)
    inputs: wbc, crp
    actions: panel.cbc, panel.inflammation, panel.renal
    advance: culture sent at drainage when indicated; systemic workup if toxic
  6. 6BRANCHING_WORKUP
    POCUS when abscess-vs-cellulitis equivocal or to find occult/deep collection (Subramaniam Acad Emerg Med 2016 PMID 27770490); CT/MRI only if deep-space/perirectal/necrotizing concern — do NOT delay surgery for imaging (IDSA 2014 SSTI Stevens PMID 24973422)
    actions: workup.le_edema
    advance: drainable collection confirmed / deep extension excluded
  7. 7DIFFERENTIAL
    Epidermal/sebaceous (epidermoid) cyst (inflamed vs infected), hidradenitis suppurativa, non-purulent cellulitis, necrotizing fasciitis, septic bursitis/arthritis, infected vascular access, pyomyositis, hematoma, lymphadenitis (IDSA 2014 SSTI Stevens PMID 24973422; Alikhan JAAD 2019 PMID 30872156)
    advance: mimics excluded; abscess phenotype assigned
  8. 8RISK_STRATIFICATION
    IDSA purulent-SSTI severity: mild (drain only) vs moderate (drain + culture + oral anti-MRSA) vs severe (drain + IV anti-MRSA, failed I&D+oral, immunocompromised, SIRS) (IDSA 2014 SSTI Stevens PMID 24973422); size >2 cm / multiple sites / surrounding cellulitis / age extremes drive adjunctive antibiotics (Talan NEJM 2016 PMID 26962903; Daum NEJM 2017 PMID 28657870)
    inputs: abscess_diameter_cm, surrounding_cellulitis_extent
    actions: calc.news2
    advance: severity class + adjunctive-antibiotic decision set
  9. 9TREATMENT
    Incision & drainage is primary curative therapy for all fluctuant abscesses (IDSA 2014 SSTI Stevens PMID 24973422); loop drainage or simple incision (packing optional — Gaspari Acad Emerg Med 2018 PMID 33037713); adjunctive TMP-SMX or clindamycin when moderate/severe or risk factors (Talan NEJM 2016 PMID 26962903 +6.9% cure; Daum NEJM 2017 PMID 28657870 +13–14% cure); IV vancomycin if severe/systemic; antibiotics NOT routinely needed for simple drained abscess in healthy host (Schmitz Ann Emerg Med 2010 PMID 20346539)
    inputs: pregnancy, creatinine
    advance: abscess drained; adjunctive antibiotic decision documented; wound-care + return precautions given
  10. 10DISPOSITION
    Outpatient I&D + observation for mild/moderate; admit IV for severe (systemic toxicity, failed outpatient I&D + oral, immunocompromise, large/multiple needing OR, danger-zone, perirectal/deep) (IDSA 2014 SSTI Stevens PMID 24973422)
    inputs: sbp, temperature
    advance: disposition documented
  11. 11MONITORING
    Wound recheck 48–72 h (response = decreased erythema/pain/induration); reassess for inadequate drainage, retained loculation, resistant pathogen, or NF if not improving (IDSA 2014 SSTI Stevens PMID 24973422)
    actions: panel.inflammation
    advance: clinical response confirmed at 48–72 h
  12. 12FOLLOWUP
    ≥2 abscesses/year → MRSA decolonization (intranasal mupirocin 5 d + chlorhexidine body wash 5–14 d ± household + hygiene; oral rifampin-based only for refractory) (Fritz CID 2012 PMID 22198793; IDSA 2014 SSTI Stevens PMID 24973422); reconsider hidradenitis suppurativa if intertriginous recurrent with sinus tracts/scarring → route to HS chronic management (Alikhan JAAD 2019 PMID 30872156)
    inputs: recurrent_abscess_count
    advance: recurrence-prevention / decolonization / HS-routing plan documented