The frequency of incidental pulmonary embolism in different CT examinations

Objective: Pulmonary embolism (PE) is commonly found in patients with oncologic and non-oncologic disease. The aim of the present study is to assess how frequently suspected, incidental and unreported PE occurs in particular CT examinations. In addition, differences in embolus distribution are to be considered. Methods: In a retrospective, single-centre study that covered a 5.5-year period, every contrast-enhanced CT examination was reviewed. The study group included 7238 patients with 11,747 CT examinations. A detailed pulmonary artery obstruction index (Mastora score) was used to assess thrombus mass and distribution. Results: PE frequency was 3.9% in oncologic patients and 6.6% in non-oncologic patients. PE was unsuspected in 54% of all PE events. Incidental PE was mostly often found in the following CT examinations: evaluation of acute pulmonary disease and follow-up staging. The thrombus mass was higher in non-oncologic patients than in oncologic patients. Furthermore, the thrombus mass was significantly lower in unsuspected PE than in suspected PE. In addition, the thrombus mass was significantly lower in unreported PE than in incidental PE. Conclusion: The radiologist should pay special attention to pulmonary vessels, even when not asked for PE, in the following CT examinations: evaluation of acute pulmonary disease and follow-up staging. Advances in knowledge: Particular CT indications are associated with a high frequency of PE. Whether PE is suspected or not and found or not highly depends on thrombus mass.