title: Sonoelastographic characteristics of abscess induration associated with therapy failure.
abstract: OBJECTIVE
  Sonoelastography can visualize components of skin and soft tissue abscesses, including the abscess cavity and surrounding induration, related to the patient's response to the infection. We speculate that characteristics of the induration surrounding an abscess may predict which abscesses will eventually fail therapy.
  
  
  METHODS
  We conducted a prospective trial of patients with a suspected skin abscess requiring surgical drainage who were enrolled from the emergency department of an urban tertiary care center. In this pilot study, all patients underwent incision and drainage for the suspected abscesses. Abscesses (n = 56) were imaged in orthogonal planes (long-axis and transverse to the body part) using B-mode sonography and elastography before incision and drainage. Telephone follow-up using a standardized questionnaire was performed 7 to 10 days after the initial drainage procedure to determine therapy failure. Physicians blinded to patient outcome analyzed the sonograms for predetermined image characteristics of the abscess induration.
  
  
  RESULTS
  All patients underwent incision and drainage, but 16.1% of patients failed therapy. Asymmetry of the surrounding induration was associated with therapy failure. A higher percentage of patients who failed therapy had asymmetry (66%; 95% confidence interval, 35.1%-88.3%) versus those who were successfully treated (12.8%; 95% confidence interval, 5.6%-25.6%; P = .003). In all patients, the mean volumes ± SD of the abscess cavity and induration were 2.2 ± 3.7 and 19.9 ± 24.7 cm, respectively, with a mean volume ratio (induration to abscess cavity) of 31.9 to 1.
  
  
  CONCLUSIONS
  We describe sonographic characteristics of the abscess induration imaged with sonoelastography that are associated with therapy failure. We found that patients with asymmetric induration visualized with sonoelastography have higher rates of therapy failure.
authors.affiliation: Department of Emergency Medicine, University of Massachusetts School of Medicine, 55 Lake Ave N, Worcester, MA 01655, USA. romolo.gaspari@umassmemorial.org
authors.forename: Romolo
authors.initials: R
authors.lastname: Gaspari
authors.forename: David
authors.initials: D
authors.lastname: Blehar
authors.forename: Justin
authors.initials: J
authors.lastname: Briones
authors.forename: Matthew
authors.initials: M
authors.lastname: Dayno
mesh_terms: D000038:Abscess / Q000000981:diagnostic imaging* / Q000601:surgery*; D000328:Adult; D016009:Chi-Square Distribution; D004322:Drainage; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D017211:Treatment Failure; D014463:Ultrasonography