Final answer:
The most likely cause of a swollen, red, and warm leg with accompanying fever is an infection, such as cellulitis, especially following a delayed cleaning of a wound as described in the patient's history.
Step-by-step explanation:
When examining a patient's lower extremities and noting one leg is swollen, erythematous (red), and warm to the touch, coupled with the patient being febrile, the most likely cause of these findings is an infection related to the wound or a cellulitis. The presence of fever, swelling, redness, and warmth indicates an inflammatory process, which is typically due to an infection. This could have been exacerbated in the case history provided by delayed wound cleaning, which can allow bacteria to enter and multiply. The inflammation described is a response of the body's immune system, which involves the movement of leukocytes and fluid to the site of infection. Another possibility, although less likely given the acute nature and presence of fever, is a condition like varicose veins or edema, but these are typically chronic and do not present with a generalized fever unless complicated by an infection such as thrombophlebitis.