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

Study objective: We hypothesize that clinical failure rates will be lower in patients treated with point-of-care ultrasonography and incision and drainage compared with those who undergo incision and drainage after physical examination alone.

Methods: We performed a prospective randomized clinical trial of patients presenting with a soft tissue abscess at a large,
academic emergency department. Patients presenting with an uncomplicated soft tissue abscess requiring incision and drainage were eligible for enrollment and randomized to treatment with or without point-of-care ultrasonography. The diagnosis of an abscess was by physical examination, bedside ultrasonography, or both. Patients randomized to the point-of-care ultrasonography group had an incision and drainage performed with bedside ultrasonographic imaging of the abscess. Patients randomized to the non–pointof-care ultrasonography group had an incision and drainage performed with physical examination alone. Comparison between groups was by comparing means with 95% confidence intervals. The primary outcome was failure of therapy at 10 days, defined as
a repeated incision and drainage, following a per-protocol analysis. Multivariate analysis was performed to control for study variables. Our study was designed to detect a clinically important difference between groups, which we defined as a 13% difference.

Results: A total of 125 patients were enrolled, 63 randomized to the point-of-care ultrasonography group and 62 to physical
examination alone. After loss to follow-up and misallocation, 54 patients in the ultrasonography group and 53 in the physical
examination alone group were analyzed. The overall failure rate for all patients enrolled in the study was 10.3%. Patients who were evaluated with ultrasonography were less likely to fail therapy and have repeated incision and drainage, with a difference between groups of 13.3% (95% confidence interval 0.0% to 19.4%). Abscess locations were predominantly torso (21%), buttocks (21%), lower extremity (18%), and axilla or groin (16%). There was no difference in baseline characteristics between groups relative to abscess size, duration of symptoms before presentation, percentage with cellulitis, and treatment with antibiotics.

Conclusion: Patients with soft tissue abscesses who were undergoing incision and drainage with point-of-care ultrasonography demonstrated less clinical failure compared with those treated without point-of-care ultrasonography. [Ann Emerg Med. 2019;73:1-7.]