Lymphedema may be caused by all of the following EXCEPT:

Lymphedema is a condition characterized by the accumulation of lymph fluid, leading to swelling, primarily in the limbs. The condition can arise from multiple causes that involve disruption or obstruction of the lymphatic system.

Obesity is generally not a direct cause of lymphedema in the same way that infection, radiation, and trauma or surgical excision are. While obesity can contribute to an increased risk of developing lymphedema due to the added pressure on the lymphatic system and potential for greater tissue inflammation, it is not a primary etiological factor. In contrast, infections can lead to lymphatic damage (such as filariasis), radiation therapy can damage lymph nodes leading to obstruction, and trauma or surgical excision of lymph pathways can directly disrupt lymphatic drainage, all of which can cause lymphedema.

Therefore, the other options directly relate to identifiable mechanisms that can lead to lymphatic dysfunction and consequent lymphedema, while obesity is more of a risk factor than a direct cause.