115 - Discrepancy between expected skin abscess incision & drainage outcome and amount of pus expressed

Poster Number: 115
Publication Number: 115.1113

Background: Incision and drainage (I&D) is the treatment of choice for pediatric skin abscesses. Discrepancies between either the estimated clinical or sonographic volume and the amount of pus expressed can be the product of poor ultrasound technique, poor I&D technique or poor estimation of the amount expressed. Regardless, these are not infrequent events in the pediatric emergency department (ED).

Objective: We sought to assess the prevalence of discrepancies between expected and expressed volumes during skin abscess I&D.

Design/Methods: A cross-sectional chart review was performed at an urban academic tertiary care pediatric ED between 2017 and 2023. We reviewed notes of all patients that had an I&D attempted for a skin abscess. We used a natural language processing program to screen ED clinical narratives in order to identify our cohort. We focused on two patient groups based off of documented abscess diameter (estimated clinically or by point-of-care ultrasound (POCUS)); abscesses with predicted volumes of < 1ml and those with predicted volumes of >10ml. The rationale was that these values correspond with decision making of ‘not worth pursuing I&D’ and ‘definitely worth pursuing I&D’, respectively.
We considered a positive discrepancy if for an expected abscess volume of < 1ml, the documented volume expressed was >10ml (underestimated), and if for an expected abscess volume of >10ml, the documented volume was < 3 ml (overestimated). We calculated prevalence with confidence intervals using descriptive statistics.

Results: We identified 606 patient meeting our inclusion criteria. 477 patients had both a POCUS abscess diameter as well as volume expressed documented, allowing calculation of POCUS-based discrepancies. 475 patients had a clinical abscess diameter as well as volume expressed documented, allowing calculation of clinical-based discrepancies. Finally, 394 patients had both a clinical and POCUS abscess diameter as well as volume expressed documented, allowing calculation of the combined impact on discrepancies.
Overall, 10.6% and 6.5% were underestimated by sonographic and clinical exam, respectively. In addition, 2.1% and 8.0% were overestimated by sonographic and clinical exam, respectively. When clinical assessment is combined with POCUS that rate decreases to 3.5% underestimated and 0.8% overestimated. Results for rate of discrepancies by evaluation method are presented in Table 1.

Conclusion(s): Combining clinical assessment with POCUS assessment of pediatric skin abscesses provides better prediction of abscess volume than reliance on a single method.