Frequency and Reliability of the Reversed Halo Sign in Patients With Septic Pulmonary Embolism Due to IV Substance Use Disorder.
AJR Am J Roentgenol. 2020 Jan;214(1):59-67. doi: 10.2214/AJR.19.21659. Epub 2019 Oct 31.
Almeida RR, Marchiori E, Flores EJ.
OBJECTIVE. The purpose of this article is to assess the "reversed halo" sign in patients with septic pulmonary embolism (PE) due to IV substance use disorder.
MATERIALS AND METHODS. A retrospective analysis was performed of chest CT scans obtained between 2007 and 2017 that had findings of septic PE associated with IV substance use disorder. Inclusion criteria were history of IV substance use disorder, findings of septic PE on chest CT scans, and confirmation of infection. Image analysis was performed by three radiologists to assess the frequency, appearance, and evolution of the reversed halo sign. Interreader agreement to characterize the reversed halo sign was assessed using kappa statistical analysis. The chi-square test was used to correlate reversed halo sign shape with evolution on follow-up scans.
RESULTS. Of 62 patients who met the inclusion criteria (54.8% women; mean age, 32.8 ± 8.3 [SD] years), 59.7% (37/62) had reversed halo signs (κ = 0.837-0.958, p < 0.0001). The mean number of unique reversed halo signs per patient was 2.1 ± 1.7 (46.7% of patients had more than one reversed halo sign). Of 78 unique reversed halo signs, 93.6% (73/78) were peripherally located and 51.3% (40/78) were located at the lower lobe, 52.6% (41/78) were pyramidal and 47.4% (37/78) were round shaped, 89.7% (70/78) had central low-attenuation areas, and 34.6% (27/78) had internal reticulations. Cavitation developed in 37.2% (29/78) of reversed halo signs and more often in pyramid-shaped ones (70.8%, 17/24), whereas consolidation occurred in 30.8% (24/78) and more often in round-shaped ones (58.6%; 17/29, p = 0.03).
CONCLUSION. Septic PE should be considered in the differential diagnosis of patients with IV substance use disorder presenting with reversed halo sign. The reversed halo sign was reliably and frequently observed on the chest CT scans of patients with IV substance use disorder-related septic PE. Characteristics of reversed halo sign presentation were identified as potential features to differentiate septic PE from other causes of pulmonary infarct manifesting with reversed halo sign.
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