Incidental pulmonary nodules detected on computed tomography pulmonary angiography: prevalence and malignancy outcomes from a Thai tertiary-care center.

Abstract

Background: Computed tomography pulmonary angiography (CTPA) is widely used for diagnosing pulmonary embolism (PE) and frequently reveals incidental pulmonary nodules. However, data regarding the prevalence and malignant outcomes of incidental pulmonary nodules, particularly among patients with PE, remain limited in Thailand. This study aimed to investigate the prevalence of incidental pulmonary nodules detected on CTPA and to evaluate malignancy outcomes, particularly in patients with concurrent PE.

Methods: This retrospective cohort study included patients aged ≥18 years who underwent CTPA at King Chulalongkorn Memorial Hospital between January 2017 and December 2018. Patients with active lung cancer or known pulmonary metastases were excluded. Clinical characteristics, CTPA findings, and follow-up data were reviewed. Pulmonary nodules were followed until a definitive diagnosis was established, until May 2024, or for a minimum of 2 years in the absence of interval growth.

Results: A total of 376 patients were included in the analysis. Incidental pulmonary nodules were identified in 129 patients (34.3%), while PE was diagnosed in 110 patients (29.3%). The prevalence of incidental pulmonary nodules did not differ significantly between the PE-positive and PE-negative groups (29.1% vs. 36.5%; P=0.17). Category-specific analyses demonstrated that patients with PE had a higher proportion of pulmonary nodules >8 mm (21.9% vs. 9.3%) and malignant outcomes (18.8% vs. 3.1%) than those without PE. Relative risks (RRs) with corresponding 95% confidence intervals (CIs) are reported in the Results section. Among the 9 patients ultimately diagnosed with malignancy, most received a definitive diagnosis within 6 months following CTPA.

Conclusions: The prevalence of incidental pulmonary nodules detected on CTPA were common and occurred more frequently than previously reported in several international studies. Patients with concurrent PE were more likely to have pulmonary nodules >8 mm and malignant outcomes than patients without PE. These findings suggest that incidental pulmonary nodules detected in patients with concomitant PE may identify a subgroup warranting careful clinical follow-up. Because of the retrospective design and limited number of malignant outcomes, larger prospective studies are required before changes to current surveillance strategies can be recommended.