Easy as 1-2-3! Point-of-Care Ultrasound Estimation of Parapneumonic Effusion Size Using Intercostal Spaces in the Pediatric Emergency Department

Background: There is limited evidence on the ability of point-of-care ultrasound (POCUS) to quantify and characterize pediatric parapneumonic effusions. This study aimed to evaluate the agreement between lung POCUS and radiology ultrasound (RADUS) or chest x-ray (CXR) in determining effusion size and complexity in children presenting to the pediatric emergency department (ED). Methods: We studied patients aged younger than 18 years diagnosed with parapneumonic effusions at the Hospital for Sick Children between June 1, 2018, and December 1, 2024. Included patients had undergone a lung POCUS demonstrating a pleural effusion and a RADUS or CXR within 36 hours of their POCUS examination. Patients with suboptimal POCUS images were excluded. Using previously described criteria, we determined whether an effusion was “drainable” or “non-drainable” using the number of involved intercostal spaces as an estimate of effusion size. Our primary outcome was the rate of agreement between the POCUS estimation of effusion size to that of RADUS (or CXR if RADUS was unavailable) using Cohen Kappa statistic. We also compared the rate of agreement between POCUS and RADUS for effusion complexity and the time taken to complete both imaging modalities. Results: Eighty-five cases were included in this study. POCUS agreed with RADUS substantially in its ability to quantify (κ=0.76) and characterize (κ=0.65) parapneumonic effusions. There was also substantial agreement between POCUS and CXR for estimating effusion size (κ = 0.71). The median time to complete POCUS was significantly shorter compared with RADUS (6 vs. 14 min; P =0.003). Conclusions: Using a simple method of counting involved intercostal spaces, our results support the use of lung POCUS for quantifying and characterizing parapneumonic effusions in the pediatric ED. Future research is needed to evaluate the generalizability of these findings and their impact on clinical outcomes.