Is ankle swelling associated with heat exhaustion or due to vasodilation?

Edema: Swelling about the ankle may have a different sources ranging from sprains and strains to increased sodium intake to lymphedema, etc.... See your physician for further eval of the edema and reccs.....

Both: Ankle swelling has many causes including vasodilation, venous insufficiency, lymphedema, high blood pressure, kidney problems, etc... Heat exhaustion will cause a temporary shut down of the kidneys, thereby also possibly causing swelling to the ankles.