Lung Embolism: Key CT Imaging Findings and Clinical Implications

When evaluating patients suspected of pulmonary embolism (PE), computed tomography (CT) plays a crucial role in accurate diagnosis. One of the most telling signs observed on standard chest CT scans is the presence of wedge-shaped areas of increased density in the lung parenchyma. These hyperdense regions typically point toward the pleura and are often indicative of pulmonary infarction—a condition where blood flow to a portion of the lung is severely reduced or completely blocked due to an embolus.

Common Radiological Signs of Pulmonary Infarction

In many cases, these wedge-shaped opacities are accompanied by additional imaging features such as decreased lung volume and impaired aeration in the affected area. This phenomenon, known as parenchymal atelectasis or poor inflation, occurs because the obstructed blood supply compromises both gas exchange and normal lung expansion. While not all pulmonary emboli lead to infarction, the presence of such CT findings strongly suggests that tissue damage has already occurred.

Role of CT Pulmonary Angiography (CTPA)

To directly visualize the causative clot, CT pulmonary angiography (CTPA) is considered the gold standard. This specialized imaging technique allows radiologists to detect filling defects within the pulmonary arteries—areas that appear as low-attenuation (dark) regions surrounded by contrast-enhanced blood flow. These defects most commonly occur in the main pulmonary artery or its segmental and subsegmental branches.

Origin of the Embolus

The majority of these clots originate from deep vein thrombosis (DVT), typically in the lower extremities. When a thrombus dislodges from the leg veins, it travels through the venous system, passes through the right side of the heart, and lodges in the pulmonary circulation. CTPA clearly captures this obstruction, providing both anatomical and clinical context for the patient's symptoms.

Hemodynamic Consequences of Major Pulmonary Embolism

A large or centrally located embolus can significantly impede blood flow through the pulmonary vasculature, leading to increased pressure in the right ventricle and right atrium. Over time, this strain results in right heart dilation—a condition referred to as acute cor pulmonale. On follow-up CT scans, clinicians may observe enlargement of the right-sided cardiac chambers, a critical indicator of hemodynamic instability and poor prognosis.

Early detection through CT imaging not only confirms the diagnosis but also helps guide treatment decisions, including anticoagulation therapy, thrombolysis, or even surgical intervention in severe cases. Understanding these CT manifestations enables healthcare providers to respond swiftly and effectively, improving patient outcomes and reducing mortality associated with pulmonary embolism.