Background Computed tomography pulmonary angiography (CTPA) is the gold standard for the diagnosis of pulmonary embolism (PE). However, contrast is contraindicated in some patients. The purpose of this study was to determine the diagnostic accuracy of unenhanced multidetector CT (MDCT) for diagnosis of central PE using CTPA as the gold standard. Methods The records of patients with suspected PE seen between 2010 and 2013 were retrospectively reviewed. Inclusion criteria were an acute, central PE confirmed by CTPA and non-enhanced MDCT before contrast injection. Patients with a PE ruled out by CTPA served as a control group. MDCT findings studied were high-attenuation emboli in pulmonary artery (PA), main PA dilatation > 33.2 mm, and peripheral wedge-shaped consolidation. Receiver operating characteristic (ROC) analysis was used to determine the sensitivity and specificity of unenhanced MDCT to detect PE. Wells score of all patients were calculated using data extracted from medical records prior to imaging analysis. Results Thirty-two patients with a PE confirmed by CTPA and 32 with a PE ruled out by CTPA were included. Among the three main MDCT findings, high-attenuation emboli in the PA showed best diagnostic performance (Sensitivity 72.9%; Specificity 100%), followed by main PA dilatation > 33.2 mm (sensitivity 46.9%; specificity 90.6%), and peripheral wedge-shaped consolidation (sensitivity 43.8%; specificity 78.1%). Given any one or more positive findings on unenhanced MDCT, the sensitivity was 96.9% and specificity was 71.9% for a diagnosis of PE in patients. The area under the curve (AUC) of a composite measure of unenhanced MDCT findings (0.909) was significantly higher than that of the Wells score (0.688), indicating unenhanced MDCT was reliable for detecting PE than Wells score. Conclusions Unenhanced MDCT is an alternative for the diagnosis of acute central PE when CTPA is not available.

A previously healthy 20-year-old man presented with a 4-day history of intractable cough and fever. A chest radiograph showed a right tracheal bronchus and a right paratracheal mass with the trachea shifted to the left (Figure 1). A contrastenhanced computed tomography scan of the chest showed a right aortic arch and compression of the trachea (Figure 2). A 3-dimensional reconstruction of a computed tomography scan of the chest in coronal view was created to make the tracheal bronchus more visible ( Figure 3). The patient's respiratory symptoms resolved after a course of oral antibiotic therapy.First described by Sandifort in 1785, 1 tracheal bronchus is an aberrant, accessory or ectopic bronchial branch arising directly from the lateral wall of the trachea 2 above the carina. It is congenital and has an incidence of about 2%.3 A right-sided bronchus such as the one we describe is not rare. Although developmental bronchial anomalies usually manifest in infancy or early childhood, some people may have no symptoms until adulthood. The anomaly may be discovered incidentally on computed tomography scans of the chest performed for some other reason. Tracheal bronchus is associated with recurrent infection and, in children, respiratory distress. Rarely, a tracheal bronchus may be intubated inadvertently during the administration of anesthesia or the treatment of respiratory failure. The resulting obstruction can cause atelectasis, postobstructive pneumonia or respiratory failure. Tracheal bronchus