Arm position on portable neonatal/infant ICU chest radiograph can mimic lamellar effusion

Arm malposition in neonatal ICU radiographs may result in overlap of the arm soft tissues and chest wall giving the appearance of lamellar effusions. We aimed to determine the frequency of arm malposition on portable neonatal/infant intensive care unit (N/IICU) chest radiographs and the proportion of these mimicking lamellar effusions.

We evaluated a subgroup of supine portable chest radiographs performed at the N/IICU. Two reviewers, at a tertiary pediatric hospital located in the USA, evaluated each radiograph in consensus and classified arm position for either side independently as (1) acceptable: arm abducted and separated from the chest and (2) compromised: arm down and in contact with chest soft tissue. The compromised cases were evaluated regarding any overlap between soft tissues of the arm and chest of sufficient degree to mimic a lamellar effusion.

We reviewed 300 radiographs performed at the N/IICU (600 hemithoraces). The mean age was 1.8 ± 1.8 months. Of 600 hemithoraces, 233 (39%) showed arms down and in contact with the chest. In seven (1%) cases, the arm position was compromised and mimicked a lamellar effusion. We identified 32 (5%) true lamellar effusions in the whole sample; in 14 of the 32 cases with lamellar effusion, the radiographs were performed with the arms down.

Portable chest radiographs performed in the N/IICU without proper arm abduction represent a potential for misinterpretation of chest radiographs. Although the prevalence of mimickers of lamellar effusion is only around 1%, the prevalence of arms down on a portable chest radiograph is considerably high (39%).