Imaging Pulmonary Embolism in the Era of Subsegmental Clots: What the Internist Needs to Know About Overdiagnosis, Anticoagulation, and Follow-Up.

The widespread adoption of multidetector computed tomography pulmonary angiography has dramatically increased detection of subsegmental pulmonary embolism (SSPE), raising critical questions about overdiagnosis, optimal anticoagulation strategies, and appropriate follow-up. Despite increased detection, observational data demonstrate remarkably low short-term recurrence rates that do not differ significantly from more proximal pulmonary embolism. However, anticoagulation carries major bleeding risks, creating clinical equipoise about net benefit in low-risk isolated SSPE. Radiologist interpretation challenges compound the problem, with a substantial proportion of segmental and subsegmental emboli missed on initial reads in some series. This review presents current evidence on the epidemiology, diagnostic challenges, treatment controversies, and outcome data for SSPE, providing internists with actionable insights for clinical decision-making. Key findings include the lack of randomized controlled trial data to guide anticoagulation decisions, substantial inter-observer variability in SSPE diagnosis, and emerging evidence that selected low-risk patients may be safely observed without anticoagulation.