US Journal Club: May, 2020 Soft-Tissue Ultrasound

Paper #1:

The Effect of Soft-tissue Ultrasound on the Management of Cellulitis in the Emergency Department

Tayal V, et al. Acad Emerg Med. 2006;13(4):384‐388. DOI:10.1197/j.aem.2005.11.074

Full text: https://onlinelibrary.wiley.com/doi/abs/10.1197/j.aem.2005.11.074

  • Introduction and background information
    • There are approximately 2 million annual visits for skin and soft tissue infections (SSTIs) per year in US Emergency Departments1
    • Differentiating cellulitis from abscess can be difficult with physical examination
    • The authors note that ultrasound in patients with clinical cellulitis without abscess has not been studied
  • What was the primary objective of this study?
    • To evaluate the effect of diagnostic soft-tissue US on management of ED patients with clinical cellulitis
  • Methods and study design
    • A prospective, observational study over 28 months at an urban ED with 100,000 visits per year
    • Inclusion criteria:
      • Age ≥18 years
      • Evidence of cutaneous soft-tissue infection
        • Defined as erythema, induration, warmth or tenderness
    • Exclusion criteria:
      • No signs of obvious abscess
        • Defined as area of flatulence, drainage, skin elevation or signs of purulence
      • No perineal infections
    • Treating physician given two question test prior to US:
      • 1) Need for further drainage procedures? (yes or no)
      • 2) Pretest probability for presence of subcutaneous fluid from 0-100 (with 10 point scale increments)
    • US performed by 5 ED physicians with >100 “typical” scans plus ≥5 soft tissue scans 
    • Used high frequency linear probes in two orthogonal planes
    • US images and interpretation was shown to treating physician and effect on management was recorded:
      • No effect
      • New drainage procedure
      • Elimination of drainage procedure
      • Consultation
      • Further imaging
      • Procedural guidance
  • Results
    • Total of 126 patients enrolled
    • Results of pre-US questions
      • 1) Felt that 35% of patients needed drainage
      • 2) Probability for subcutaneous fluid 35.5%
    • Ultrasound by EP found signs of abscess in 50% of patients
    • No significant difference in detection of fluid between those believed to need and not likely to need drainage  
    • US changed management in 56% of patients – and was most likely to influence the group believed needed further intervention
      • In the group not believed to need further drainage, US changed management 48% of cases – with all patients receiving drainage found to have an abscess
      • In the group believed to need further drainage, US changed management in 73% of cases – with about half no longer needing drainage and half who needed further guidance, testing or consultation 
  • Discussion
    • Cellulitis may hide occult abscess formation
    • For low pretest probability patients: management change was the presentation of an abscess requiring drainage
    • For high pretest probability: change was opposite, half did not require drainage
    • Even at very low pretest probability the benefit holds
  • Were there limitations?
    • EPs only had 5 SSTI ultrasounds performed, could limit accuracy
    • Unclear of the exact training level of those performing the tests
    • Likely significant variability in agreement of clinical cellulitis on exam
  • Take-home points
    • Cellulitis versus abscess can be difficult to assess via physical exam
    • Authors evaluated if US would change management in clinically apparent cellulitis
    • In patients with low pretest probability for further drainage, almost half of cases ended up requiring drainage for an abscess
    • In those with high pretest probability, more than half either did not need drainage or needed further work-up

References

  1. May L, et al. Incidence and factors associated with emergency department visits for recurrent skin and soft tissue infections in patients in California, 2005-2011. Epidemiol Infect. 2017;145(4):746‐754. doi:10.1017/S0950268816002855

Paper #2:

Abscess Incision and Drainage With or Without Ultrasonography: A Randomized Controlled Trial

Gaspari R, Sanseverino A, Gleeson T. Ann Emerg Med. 2019 Jan;73(1):1-7. doi: 10.1016/j.annemergmed.2018.05.014. 

Full text: https://pubmed.ncbi.nlm.nih.gov/30126754/

  • Introduction and background information
    • POCUS has been used clinically for patients presenting to the ED with an abscess, however there is limited literature supporting its use
  • What was the purpose of the study?
    • Hypothesis: clinical failure rates would be lower in patients treated with POCUS and I&D compared to those who received I&D after physical examination alone
  • Methods and study design
    • Prospective randomized controlled trial of adult patients who presented to the ED with an uncomplicated soft tissue abscess
    • Patients randomized to 
      • US, physical exam, and I&D
      • Physical exam and I&D 
    • Inclusion criteria:
      • Patients who presented to ED with suspected skin abscess requiring I&D
      • Atraumatic swelling, pain, or erythema consistent with an abscess cavity
    • Exclusion criteria
      • If patients were clinically ill (fever, hypotension, or “appeared clinically ill”)
      • If the abscess was due to an animal bite or foreign body trauma
      • Excluded paronychia, dental, genital, peritonsillar abscesses
      • If the patient was unable to consent
    • Information collected: demographics, PMH (incl DM, IVDU, hx abscess), abscess characteristics, symptoms
    • Abscess measurement included the length times width of fluctuance from outer edges, or outer edges of induration
    • US imaging was standardized for acquisition and interpretation
    • Used a high frequency linear array probe to obtain images in short and long axis 
    • Images were Interpreted as positive or negative for abscess
      • Definition: hypoechoic focus with surrounding induration or hyperechoic or isoechoic focus with posterior acoustic enhancement and surrounding induration
    • US incorporated into I&D was not standardized, with 3 possible options
      • Static images take prior to I&D
      • Dynamic guidance during I&D
      • Comprehensive guidance with cycles of images before and after I&D, repeated as necessary if multiple attempts were required
    • US performed by EM faculty and residents experienced with soft tissue US
    • Both groups received:
      • Local anesthesia, linear incision, +/- wick placement and/or antibiotics
      • Instructed to return in 2-3 days for repeat exam (68% success)
      • Each were contacted 10 days later and asked a series of questions about their symptoms
    • Primary outcome:  failure of therapy, requiring repeat I&D that produced purulence determined at 10 day point after phone follow up
    • Secondary outcomes: need for additional antibiotics or continued symptoms (pain and purulence)
    • Initial estimate of failure rates after physical exam alone was 20%, failure rates after US = 7%
  • Results:
    • 125 patients enrolled between Jan 2015 to July 2017, 63 into US, 62 into physical exam alone. After loss to follow up there were 54 US and 53 physical exam
    • 15 randomized to physical exam only required US before I&D
    • Several deviations including one patient that required OR for I&D, some patients received antibiotics only 
    • Overall clinical failure rate 10.3%
    • Failure rate for US 3.7%, for PE 17.0%, difference of 13.3% (CI 0.0-19.4)
    • I&D’s performed by 50 physicians including senior residents and faculty, no cluster of failures among a single provider
    • Those requiring 2nd I&D usually for 1 of 2 reasons:
      • #1. increased/constant pain with palpable fluctuance without purulence with manual compression, typically presented within 3 days
      • #2. retained abscess cavity
    • Findings at follow up 
      • Continued symptoms: pain (33.6%), purulence (22.4%)
      • Majority on antibiotics when presenting to ED or started on after procedure (57%)
      • Majority reported improvement in symptoms (78.5%)
      • No clinical difference in abscess characteristic between groups
  • Limitations: 
    • Not all abscesses that presented to the ED were enrolled which may yield a selection bias
    • Impossible to blind patients and  physicians due to the nature of the study
    • Two patients had follow up with research staff who were not blinded
    • Small n, wide CI 
  • Discussion:
    • Patients who underwent I&D without US were more likely to fail therapy and require repeat I&D
    • Failure is likely due to retained purulence from inadequate drainage
    • Failure was mostly like to occur in the first few days, but if untouched, may have resolved on their own
    • US guidance was not standardized for I&D so possible for variations in technique may result in different outcomes
    • Antibiotic use was not associated with clinical cure. There are several published studies that evaluate the efficacy of antibiotic use for abscess, and this concept may be combined with US to decreased antibiotic use in a future study
    • Speculate that US improves ID through
      • Better planning of initial incision
      • Better execution of procedure
      • Accurate assessment of residual purulence
  • Take home point:
    • Patients who underwent I&D without US were more likely to fail therapy and require  repeat I&D, though these results may not be clinically significant

Paper #3:

Diagnosis of necrotizing fasciitis with bedside ultrasound: The STAFF Exam

Castleberg E, et al. West J Emerg Med. 2014;15(1):111‐113. DOI:10.5811/westjem.2013.8.18303

Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935782/

  • Introduction
    • Necrotizing fasciitis is a life threatening, rapidly progressing infection of the fascia and subcutaneous tissues
    • The morbidity and mortality is significant, between 25 to 75%, along with prolonged length of hospital stay
    • Necrotizing fasciitis is a clinical diagnosis requiring operative management, but in ambiguous cases CT or MRI is traditionally used to confirm the diagnosis
  • Case Report
    • The authors present the case of a 44 year old female who presented to the ED with 3 days left groin/thigh redness and fevers
    • Was first seen at an urgent care, treated with IV vancomycin and discharged on on oral antibiotics
    • Within 24 hours presented to the ED with tachycardia and tachypnea
    • Was noted to have a large area of induration, crepitus was difficult to assess
    • Her labs showed elevated WBC and lactate; LRINEC score 6
    • EPs performed a soft tissue ultrasound and propose the following ultrasound exam mnemonic:
      • STAFF Exam
        • Subcutaneous
        • Thickening
        • Air
        • Fascial
        • Fluid
    • Subsequently taken to OR with large washout with prolonged ICU stay; discharged fully ambulatory
  • Discussion
    • The diagnosis of necrotizing fasciitis is clinical but with a wide range of presentations and difficult to distinguish between cellulitis/erysipelas
    • Only 53% are febrile
    • Rarely are large bullae or drainage seen
    • CT and MRI can be time consuming and delay definitive management
    • When performing ultrasound, look for subcutaneous thickening, subcutaneous air and fascial fluid accumulation
    • The authors cite a 62 patient observational review of US for necrotizing fasciitis showing sensitivity of 88% and specificity of 93%1 
    • They noted that ultrasound alone cannot rule out necrotizing fasciitis but if characteristic findings are seen, can allow foregoing of time consuming imaging and lead to faster OR transfer
  • Take home points
    • The diagnosis of necrotizing fasciitis is clinical but can be difficult due to the varied presentations; CT and MRI, used in difficult cases, can further delay definitive management
    • This case showed the use of ultrasound with the STAFF mnemonic to highlight typical features seen
    • Although US alone is not able to safely rule out necrotizing fasciitis, its can help to reduce delays to the OR in some patients

References

  1. 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. doi:10.1111/j.1553-2712.2002.tb01619.x

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