Factors related to the failure of radiographic recognition of occult posttraumatic pneumothoraces.

Purpose: Although posttraumatic pneumothoraces (PTXs) are common and potentially life threatening, the supine chest radiograph (CXR) is an insensitive test for their detection. Computed tomography (CT) often identifies occult pneumothoraces (OPTXs). Previous descriptions of OPTX topography have been poor. Our purpose was to define their distribution and aid in the targeting of thoracic ultrasound.
Methods: Posttraumatic supine CXRs and CTs were reviewed for occult, overt, and residual PTXs. PTXs were compared according to their apical, basal, anterior, lateral, medial, and posterior components. A comparative size index was calculated.
Results: Among 761 patients, 338 CT scans revealed 103 PTXs in 89 patients; 55% were OPTXs. OPTXs were apical (57%), basal (41%), anterior (84%), lateral (24%), and medial (27%), with 0% posterior.
Conclusions: CXR missed over half of all PTXs. OPTXs had a greater anterior versus lateral (nearly 4-fold) and both basal and apical versus lateral (2-fold) distribution. OPTXs are often located at easily accessible sonographic windows.