The frequency of incidental pulmonary embolism in different CT examinations

Abstract

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.

Incidental pulmonary embolism in oncologic patients—a systematic review and meta-analysis

“…There are also controversies of the clinical relevance of IPE. So, IPE is more often located on the segmental and subsegmental level without an occlusion of the vessel [ 1 , 30 , 31 ]. Correspondingly, the total embolic burden in incidental PE is lower than that in symptomatic PE [ 30 – 32 ].…”

Management of incidental pulmonary embolism

“…Subsegmental PE was not observed in any of the 60 incidental PE diagnoses on CT scan with 4-row technology or less, ( pooled frequency 0%, 95% CI 0-6.0) [24,[34][35][36], whereas 34 of the 173 PE diagnoses on multi-row-detector CT were limited to the subsegmental pulmonary arteries ( pooled weighted frequency 23%, 95% CI 6.7-40; figure 3) [28,[31][32][33]38]. Notably, on average, the total embolic burden in incidental PE is lower than that in symptomatic PE [23,43,46]. In one study, the median Qanadli score index was 16% lower in 48 patients with incidental PE, compared to a reference cohort of 113 patients with symptomatic PE, even with 40% of all incidental PEs located in the main pulmonary arteries [46][47][48].…”

“…The reported frequency of incidental PE on routine CT-imaging of the chest varies among different patient categories, and has increased over time with the introduction of more advanced multi-slice CT machines. Generally, incidental PE is most often observed in CT scans performed for the evaluation of acute pulmonary disease and cancer staging [23]. In cancer patients, the only study available that has assessed incidental PE in 385 chest-CT scans using a 4-row CT scanner reported an incidence frequency of 2.6% (95% confidence interval [CI] 1.2-4.7) [24].…”

“…Notably, most patients in these cohorts were referred for either cancer diagnosis or follow-up as well. One study focussed on the frequency of incidental PE detected on multi-slice chest CT in trauma patients, and reported a notable 24% (95% CI [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] showing PE [38]. Furthermore, the pooled weighted frequency of incidental PE on multi-slice coronary CT in a total of 7019 patients from four studies is 1.1% (95% CI 0.68-1.6) (figure 2) [39][40][41][42].…”

Low contrast volume dual-energy CT of the chest: Quantitative and qualitative assessment

“…In about two-thirds of DECT-R exams, the contrast enhancement in subsegmental branches was suboptimal and justifies the usage of different injection protocol for DECT-PA where pulmonary embolism is suspected. However, it is unclear if patients with isolated or incidental subsegmental pulmonary embolism require treatment [32].…”