Last reviewed: March 2026
Contents
MDM Templates
Abscess
Patient presents with a focal area of swelling, induration, and fluctuance consistent with subcutaneous abscess. They are afebrile, non-toxic, without surrounding cellulitis extending beyond the abscess margin, and without crepitus or pain out of proportion to exam.
Presentation is most consistent with simple cutaneous abscess. History and exam lower suspicion for necrotizing fasciitis, pyomyositis, osteomyelitis, or Sporotrichosis.
Plan: Incision and drainage performed with acceptable resolution. Wound packed with iodoform gauze. Antibiotics prescribed — TMP-SMX DS 1 tab PO BID x 5-7 days for MRSA coverage given abscess >2 cm / surrounding cellulitis.
Disposition: Discharge with wound care instructions (packing removal in 24-48 hours, warm compresses, daily repacking if needed). PCP follow-up in 48 hours for wound check. Return precautions for fever, worsening redness, or spreading pain.
Cellulitis
Patient presents with unilateral erythema, warmth, and tenderness without fluctuance, crepitus, or pain disproportionate to exam. They deny fever, rigors, or rapid progression. No history of immunocompromise, recent treatment failure, or IV drug use.
Presentation is most consistent with simple cellulitis. History and exam lower suspicion for abscess requiring drainage, necrotizing fasciitis, DVT, osteomyelitis, or septic arthritis.
Plan: Cephalexin 500 mg PO QID x 7 days. Elevate affected extremity. Skin marking with pen to track progression.
Disposition: Discharge with return precautions for worsening redness beyond marked borders, fever, blistering, or crepitus. PCP follow-up in 48 hours.
Admit if: Facial cellulitis, periorbital cellulitis, failed outpatient antibiotics, toxic-appearing, immunocompromised, rapidly progressing, or concern for deeper infection.
Osteomyelitis
Patient presents with focal bone pain, erythema, and constitutional symptoms concerning for osteomyelitis. There is a plausible mechanism — contiguous spread from overlying wound / hematogenous seeding / direct inoculation from trauma or surgery.
History, exam, and imaging raise concern for osteomyelitis. This is not a condition reliably excluded in the ED — early osteomyelitis can have normal plain films and nonspecific labs. Presentation warrants admission for advanced imaging, cultures, and IV antibiotics.
Plan: Vancomycin IV for empiric MRSA coverage. Additional gram-negative and anaerobic coverage added for diabetic foot-related osteomyelitis (ceftriaxone + metronidazole).
Disposition: Admit for MRI, possible bone biopsy for culture, and IV antibiotics. Infectious disease and orthopedic or surgical consultation.
Diabetic Foot Ulcer
Non-infected ulcer:
Patient presents with a diabetic foot ulcer that does not probe to bone and is without significant erythema, tenderness, purulence, or warmth. No systemic signs of infection.
Presentation is consistent with non-infected diabetic neuropathic ulcer. History and exam lower suspicion for osteomyelitis, abscess, necrotizing fasciitis, or acute limb ischemia.
Plan: Moist wound dressing, offloading of pressure with appropriate footwear. No antibiotics indicated for non-infected ulcers.
Disposition: Discharge with PCP or wound care follow-up within 1 week.
Infected ulcer:
Plan: Antibiotic selection per severity (see education section). Probe to bone — if positive, osteomyelitis is likely.
Disposition: Admit if moderate-to-severe infection (extending >2 cm from ulcer, deep tissue involvement, systemic toxicity, vascular compromise). Discharge for mild infection (limited cellulitis <2 cm) with cephalexin and close follow-up.
Gangrene
Dry gangrene:
Patient presents with well-demarcated, desiccated tissue without infection, active drainage, or surrounding cellulitis. No evidence of acute limb ischemia (preserved pulses, no rest pain in viable tissue).
Presentation is consistent with dry gangrene from chronic arterial insufficiency. History and exam lower suspicion for wet gangrene, acute limb ischemia, necrotizing fasciitis, or DVT.
Plan: Keep area clean and dry. No antibiotics unless superinfection develops.
Disposition: Discharge with vascular surgery referral for possible revascularization or amputation planning. PCP follow-up within 1 week.
Wet gangrene:
Patient presents with necrotic tissue with purulent drainage, crepitus, surrounding cellulitis, and systemic toxicity. This is a surgical emergency.
Plan: Broad-spectrum antibiotics (vancomycin + piperacillin-tazobactam), aggressive IV resuscitation, blood cultures, lactate.
Disposition: Emergent surgical consultation for debridement or amputation. Admit to ICU if hemodynamically unstable.
Clinical Education
Cellulitis Antibiotic Selection
| Scenario | Outpatient | Inpatient |
| Non-purulent cellulitis (no abscess) | Cephalexin 500 mg PO QID | Cefazolin 2g IV q8h |
| Purulent cellulitis or MRSA risk | TMP-SMX DS BID + cephalexin 500 mg QID | Vancomycin 15-20 mg/kg IV |
| Severe / septic / failed outpatient | N/A — admit | Vancomycin + piperacillin-tazobactam |
Per 2014 IDSA guidelines: Non-purulent cellulitis is typically caused by beta-hemolytic streptococci and does not require MRSA coverage. Purulent infections (abscesses, infected wounds) are more likely MRSA.[1]
MRSA Risk Assessment
Think MRSA with: purulent infection (abscess), prior MRSA history, IVDU, recent incarceration, close contacts with MRSA, dialysis, recent hospitalization, or failed first-line antibiotics. In these patients, add TMP-SMX or doxycycline for outpatient coverage, or vancomycin for inpatient.[1]
Necrotizing Fasciitis Red Flags
Necrotizing fasciitis is a clinical diagnosis — don’t wait for imaging to consult surgery. Key red flags: pain out of proportion to exam (the hallmark finding), rapidly progressing erythema, dusky or necrotic skin, bullae or hemorrhagic blisters, crepitus on exam, systemic toxicity with sepsis, and WBC >15 or <4 with bandemia.[2]
CT findings: Fascial thickening, fat stranding along fascial planes, gas tracking (specific but not sensitive). A normal CT does not rule out early nec fasc. If clinical suspicion is high, go straight to OR for surgical exploration — the definitive diagnostic and therapeutic intervention.
Diabetic Foot Infection Classification
IDSA classification guides disposition:[3]
| Severity | Criteria | Management |
| Mild | Cellulitis <2 cm from wound, superficial | Outpatient oral antibiotics (cephalexin) |
| Moderate | Cellulitis >2 cm, deep tissue involvement, no SIRS | Admit, IV antibiotics (cefazolin or ceftriaxone + metronidazole) |
| Severe | SIRS, sepsis, limb-threatening ischemia | Admit, vancomycin + piperacillin-tazobactam, surgical consultation |
Probe-to-bone test: If a sterile metal probe passes through a diabetic foot ulcer and contacts bone, the positive predictive value for osteomyelitis is ~89%. This simple bedside test can guide imaging and antibiotic decisions.[3]
Pseudomonal risk factors: Warm climate, frequent water exposure, puncture wounds through shoes. Add ciprofloxacin or anti-pseudomonal coverage if present.[3]
References
- Stevens DL et al. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the IDSA. Clin Infect Dis. 2014;59(2):e10-e52. PubMed
- Wong CH et al. The LRINEC Score: A Tool for Distinguishing Necrotizing Fasciitis from Other Soft Tissue Infections. Crit Care Med. 2004;32(7):1535-1541. PubMed
- Lipsky BA et al. 2012 IDSA Clinical Practice Guideline for the Diagnosis and Treatment of Diabetic Foot Infections. Clin Infect Dis. 2012;54(12):e132-e173. PubMed
tydotphrase.com 