While ultrasonography provides little benefit when clinicians are certain of whether an abscess is present or absent, it provides useful information and changes drainage decisions when emergency department (ED) clinicians are uncertain of abscess location, according to a new study published in the Annals of Emergency Medicine.

American researchers sought to examine the ability of ultrasonography to accurately detect the location of an abscess in order to influence drainage decisions in skin and soft tissue infections. In a trial that enrolled ED patients >12 years old with skin and soft tissue infections, clinicians were asked to perform ultrasonography on all suspected abscess cases and record their findings and planned management before ultrasonography and after ultrasonography along with actual treatment undertaken. The frequency with which final management differed from the initial planned management was recorded. Patients were also followed up with for data on whether they required subsequent ultrasonography, incision and drainage, and whether that drainage was purulent.

Among 1216 patients evaluated, clinicians were uncertain of abscess presence in 8.6% of cases (n=105) and certain in 91.4% of cases (n=1111). Based on surgical exploration and follow-up through 1 week, sensitivity and specificity for abscess detection were 90.3% and 97.7% by clinical evaluation and 94.0% and 94.1% by ultrasonography, respectively. In the 1111 cases for which the clinician was certain, sensitivity and specificity of clinical evaluation were 96.6% and 94.4% compared with an ultrasonographic evaluation sensitivity and specificity of 95.7% and 96.2%, respectively. Among the 105 uncertain cases, sensitivity and specificity of ultrasonography were 68.5% and 80.4%.

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Ultrasonography changed management of a patient’s case in 1.2% of certain cases (n=13), appropriately in 76.9% (10 of 13 cases) and inappropriately in 23.1% (3 of 13 cases). Of the 105 uncertain cases, ultrasonography changed management in 23.8% (n=25), appropriately in 84.0% (21 of 25 cases) and inappropriately in 16.0% (4 of 25).

Limitations of this study included that the patients had less severe infections and therefore had greater diagnostic uncertainty based on clinical examination and perhaps a greater utility of ultrasonography compared with populations who exhibit more significant disease. Also, enrollment in the main study was limited to those with abscesses and erythema greater than 2 cm in diameter. Therefore, discriminating ability of clinical evaluation or ultrasonography on smaller lesions could not be studied.

Researchers concluded that ultrasonography rarely changed management when clinicians were certain about the presence or absence of an abscess. As a result, “when clinicians are certain an abscess is present or absent according to clinical evaluation alone, they should proceed with appropriate management on the basis of their judgment.” When they are uncertain, “ultrasonography can provide useful information to better target need for surgical exploration and drainage.”

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Reference

Mower WR, Crisp JG, Krishnadasan A, et al. Effect of initial bedside ultrasonography on emergency department skin and soft tissue infection management [published online March 26, 2019]. Ann Emerg Med. doi:10.1016/j.annemergmed.2019.02.002