The Case

46yo female with PMH of hypertension, diabetes, ESRD on hemodialysis, PEs on warfarin, irritable bowel syndrome who presented to the emergency department for nausea, vomiting, and lower abdominal wound. She stated that she developed a lower abdominal rash two weeks prior to this for which she was started on erythromycin. She subsequently developed a “second rash” on her abdomen with anesthesia over the affected area as well as nausea, vomiting, and intolerance to oral intake for the past 4-5 days. ROS otherwise negative.

Vital Signs: T 96.9F, BP 99/56, HR 82, RR 16, SpO2 98%

Physical exam was notable for a large area of necrotic-appearing tissue in her lower abdomen with surrounding erythema, warmth, and crepitus extending from just below the umbilicus inferiorly to the vagina and laterally from one ASIS to the other. She had tenderness with palpation over lower abdomen with decreased sensation to the overlying skin. She also had a erythematous rash with scattered papules extending from bilateral flanks up into her inframammary folds.

She received IV fluids and broad spectrum antibiotics (vanc/zosyn/clindamycin) for necrotizing infection. She also received Kcentra and Vitamin K as her INR exceeded 11.

Point-of-care ultrasound showed the following:

POCUS findings: Scattered hyperechoic/echogenic foci with “dirty” posterior shadowing within the subcutaneous tissue with small amount of patchy fluid. Findings consistent with necrotizing infection.

Clinical course continued: CT abdomen/pelvis showed extensive necrotizing fasciitis throughout lower abdomen and pelvis. Surgery was consulted and she was emergently taken to the OR for debridement. She survived the OR but remained critical, in septic shock refractory to multiple pressors, and unfortunately died a little over 24 hours after surgery.

Necrotizing Fasciitis

BRIEF BACKGROUND [1]

Rapidly progressing infection of the deep soft tissue with high morbidity/mortality
Types
- Polymicrobial (type 1) aerobic/anaerobic. Tends to affect older adults and those with comorbidities
- Monomicrobial (type II) most commonly caused by group A strep
Presentation
- Signs/sx include: erythema, edema, pain out of proportion, crepitus, bullae, ecchymosis—>necrosis, cutaneous anesthesia
- May have systemic illness (fever, hypotension, MSOF, etc)
Management
- Surgical debridement is critical
- Broad spectrum antibiotics (i.e. vanc/zosyn+ clindamycin)
- As always, ABCs/resuscitate as indicated

Evaluating for Necrotizing SSTI Using POCUS

Technique

Linear transducer over the affected area
Scan & fan through entire area in both long and short axis to evaluate extent of infection & to ensure you don't miss anything

Findings

Thickening of tissue
Deep fluid collections (along fascia)
- Differentiates necrotizing infection from cellulitis
- Increased specificity and PPV [3]
- >4 mm in thickness = sensitivity of 88.2%, specificity 93.3% [4]
Fascial irregularity
Subcutaneous air — appears hyperechoic foci with dirty posterior shadowing
- Pathognomonic; later finding? [5]

**Useful mnemonic: STAFF (subcutaneous thickening, air, fascial fluid) [6]

Why Does This Matter?

Necrotizing infections are life-threatening, prompt recognition is key, and POCUS is a useful adjunct to clinical assessment, especially in unstable patients that you don't want to send out of the ED for imaging. It's generally a better rule in (than rule out) test but evidence is limited.

POST BY: DR. DENIZ EREN, PGY1

FACULTY EDITING BY: DR. LAUREN MCCAFFERTY

References

Hakkarainen TW, Kopari NM, Pham TN, et al. Necrotizing soft tissue infections: review and current concepts in treatment, systems of care, and outcomes. Current Problems in Surg. 2014;51:344-362.
Oelze, Wu S, Carnell J. Emergency ultrasonography for the early diagnosis of necrotizing fasciitis: a case series from the ED. Am J Emerg Med. 2013 Mar; 31(3): 632.e5–632.e7.
Lin CN, Hsiao CT, Chang CP, et al. The relationship between fluid accumulation in ultrasonography and the diagnosis and prognosis of patients with necrotizing fasciitis. Ultrasound Med Biol. 2019; 00(00):1-6.
Yen ZS, Wang HP, Ma HM, Chen SC, Chen WJ. Ultrasonographic screening of clinically-suspected necrotizing fasciitis. Acad Emerg Med. 2002;9(12):1448-1451.
Wronski M, Slodowski M, Cebulski W, Karkocha D, Krasnodebski IW. Necrotizing Fasciitis: Early Sonographic Diagnosis. J Clin Ultrasound. 2011;39(4):236-239.
Castleberg E, Jenson N, Dinh VA. Diagnosis of necrotizing faciitis with bedside ultrasound: The staff exam. West J Emerg Med. 2014;15(1):111-113.

POCUS BLOG MAIN PAGE

Intern Ultrasound of the Month: Necrotizing Fasciitis