A patient presents with acute unilateral lower extremity swelling. What is the best examination to be performed at that time?

In the context of a patient presenting with acute unilateral lower extremity swelling, the examination that is most appropriate is Duplex sonography. This imaging modality combines traditional ultrasound techniques with Doppler ultrasonography, allowing for both anatomical visualization and assessment of blood flow within the venous system.

Duplex sonography is particularly effective for diagnosing conditions like deep vein thrombosis (DVT), which is often a cause of sudden swelling in one leg. It enables the sonographer to visualize the veins, identify any thrombus (clots), and evaluate the venous flow dynamics, which is critical in diagnosing potential vascular issues that may necessitate immediate medical intervention.

While Doppler ultrasonography alone is useful, it does not provide the same level of detailed anatomical context that Duplex evaluates. Other imaging modalities like CT scans and X-rays do not typically address vascular issues with the same precision and are not the first choice for evaluating acute leg swelling linked to possible venous thromboembolism. Thus, Duplex sonography stands out as the preferred examination for accurate diagnosis in this clinical scenario.