Incidental central pulmonary emboli in outpatients with deep vein thrombosis

BACKGROUND: While it has been demonstrated that large asymptomatic pulmonary embolism (PE) can occur, many studies have assessed inpatients or patients with known risk factors for venous thromboembolism (such as malignancy). There are few data regarding incidental PE in outpatients with deep vein thrombosis (DVT) or assessing whether these emboli occur centrally or peripherally in the pulmonary arteries. AIMS: To determine the rates of incidental central and peripheral PE in outpatients with proximal and distal DVT. METHODS: This was a retrospective cross-sectional study of 120 patients attending our community imaging clinic between January 2015 and March 2020, with ultrasound-confirmed lower limb DVT, and subsequent computed tomography pulmonary angiogram (CTPA) within 24 h. Exclusion criteria were symptoms indicative of PE. Imaging reports were retrospectively reviewed to record the proximity of DVT and the location of any PE as either central (pulmonary trunk or main pulmonary arteries) or peripheral (lobar, segmental or subsegmental pulmonary arteries). RESULTS: Incidental PE occurred in 71 patients (59.2%), with a rate of 77.5% in proximal and 50.0% in distal DVT. Sixteen patients had central PE (13.3% of all patients with DVT; 22.5% of all patients with PE). Two patients (both with proximal DVT) had PE in the pulmonary trunk. CONCLUSIONS: Incidental PE occur frequently in outpatients with lower limb DVT, including the possibility of asymptomatic central emboli. Further studies with larger patient cohorts would be useful to assess the utility of baseline chest imaging in outpatients with DVT.