Name: Cellulitis & abscess — bulletproof documentation — ER Toolkit
Creator: Kim Trinh, MD

Most skin and soft-tissue infections are simple cellulitis or a drainable abscess — but the necrotizing infection can look subtle for hours before it kills, and half of "cellulitis" that doesn't improve isn't infection at all. The defensible chart documents the necrotizing-infection assessment, the purulent-vs-nonpurulent decision (and the ultrasound that settled it), and the MRSA-vs-strep antibiotic rationale.

01What's at stake

The catastrophic miss is necrotizing soft-tissue infection — pain out of proportion to a deceptively ordinary-looking limb, progressing over hours. The expensive misses are draining (or not draining) an abscess on a guess instead of ultrasound, treating MRSA where strep coverage would do (or vice versa), and chasing "antibiotic failure" in what is really a DVT, a contact dermatitis, or a post-vaccine reaction.

02Can't-miss diagnoses

Necrotizing soft-tissue infection — pain out of proportion, rapid progression, bullae (esp. hemorrhagic), necrosis, crepitus, skip lesions, systemic toxicity → stabilize, broad-spectrum antibiotics + clindamycin, and urgent surgery — imaging must not delay it. → pain out of proportion
DVT as a cellulitis mimic — unilateral warm swollen leg without a clear portal; consider before committing to antibiotics. → mark the margin, reconsider
Septic joint near/under the cellulitis — don't aspirate through infected skin; consider the joint.
The toxic/septic patient — fever, tachycardia, hypotension mark a more serious infection needing admission/source control.
Special exposures — water (Vibrio/Aeromonas), animal/human bites (Pasteurella/Eikenella), the very young, and the immunocompromised change coverage and disposition.

03Cellulitis vs abscess (and the mimics)

Purulent vs nonpurulent drives therapy: nonpurulent cellulitis/erysipelas → strep + MSSA; purulent abscess → drainage + S. aureus (MRSA-aware) coverage. → purulent?
Point-of-care ultrasound for the equivocal lump — cobblestoning (cellulitis) vs a hypoechoic collection (abscess); it changes management, avoids unnecessary incision, and prevents return visits. → POCUS
Mark the margin / reassess: when "cellulitis" isn't responding, reconsider DVT, stasis or contact dermatitis (linear lesions, pruritus), gout, hidradenitis suppurativa, and post-vaccine/Arthus reactions.
Blood cultures are low-yield in uncomplicated SSTI — reserve for severe immunocompromise, NSTI, instability, or prolonged fever.

Skip the typing

Work the case in the Cellulitis & Abscess Workup — it records the necrotizing-infection assessment, margin marking, source control (I&D), and host factors, and assembles an MDM that documents the can't-miss infection and the antibiotic rationale.

04Management

Abscess: incision & drainage is the primary therapy (loop drainage preferred over packing). Add antibiotics for systemic signs, surrounding cellulitis, large or sensitive-area lesions, the very young, immunocompromise, or an inadequate I&D.
Antibiotics: nonpurulent cellulitis → cephalexin (cefazolin/vancomycin if more severe); purulent/MRSA → TMP-SMX, clindamycin, or doxycycline. MRSA prevalence has fallen — direct empiric therapy by your local antibiogram. Most uncomplicated SSTIs need only 5–7 days.
Necrotizing infection: vancomycin + piperacillin-tazobactam + clindamycin and emergent surgical debridement.
Disposition: systemic toxicity → admission/source control; otherwise discharge with 48–72 h follow-up, a wound check after I&D, and clear return precautions.

05What to document

▼ weak

"Red, warm leg. Cellulitis. Started antibiotics, discharged."

▲ defensible

"Left lower-leg erythema/warmth, mild tenderness proportionate to exam — no pain out of proportion, no bullae/crepitus/necrosis/skip lesions, no systemic toxicity (afebrile, normal vitals): no features of necrotizing infection. Nonpurulent; POCUS shows cobblestoning without a drainable collection — no I&D needed. DVT considered (clear portal of entry, low pretest probability). Margin marked. Nonpurulent cellulitis → cephalexin per local antibiogram (MRSA coverage not required). Return precautions for spreading past the marked margin, severe/worsening pain, fever, bullae, or dark skin; 48-hour follow-up arranged."

06Where charts fail

Calling pain out of proportion "cellulitis" and missing the necrotizing infection (or waiting on imaging before surgery).
Draining or not draining an abscess on a guess when ultrasound would have settled it.
No documented purulent-vs-nonpurulent or MRSA-vs-strep rationale.
Discharging a febrile/tachycardic patient as "mild cellulitis."
Chasing "antibiotic failure" without reconsidering DVT, dermatitis, hidradenitis, or a post-vaccine reaction; no margin marking or return precautions.

07Sources

Patel S, Singh P. Emergency department diagnosis and management of skin and soft-tissue infections in children. Pediatric Emergency Medicine Practice (EB Medicine). 2025;22(4).
Stevens DL, Bisno AL, Chambers HF, 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.
Daum RS, Miller LG, Immergluck L, et al. A placebo-controlled trial of antibiotics for smaller skin abscesses. N Engl J Med. 2017;376(26):2545-2555.
Fernando SM, Tran A, Cheng W, et al. Necrotizing soft tissue infection: diagnostic accuracy of physical examination, imaging, and the LRINEC score. Ann Surg. 2019;269(1):58-65.

Cellulitis & abscess: documentation that holds up