Which of the following is a common cause of localized edema?

Localized edema occurs when excess fluid accumulates in a specific area of the body, often due to local factors rather than systemic conditions. One of the most common causes of localized edema is venous obstruction. When there is blockage or obstruction in the venous system, such as from a thrombus or external pressure, blood flow returns less efficiently to the heart. This stagnation leads to an increase in hydrostatic pressure within the affected veins, causing fluid to leak into the surrounding tissues, which manifests as edema in that localized area.

In contrast, heart failure tends to cause systemic edema rather than localized swelling, affecting multiple areas of the body due to the heart's inability to efficiently pump blood. Kidney dysfunction also typically results in systemic fluid retention because the kidneys are less capable of regulating fluid balance, leading to generalized edema. Similarly, systemic infections usually lead to widespread inflammatory responses, which can result in generalized swelling rather than localized edema. Therefore, venous obstruction is specifically associated with localized swelling, making it the correct choice.