I have blotchy purple marks, almost like burst bliod vessels, on the back of both my calves for the last couple of months. what causes this?

Purple Marks: If the marks look like bruises, this suggests an underlying bleeding diathesis and you should get it checked immediately. If they look more like "varicose veins, " this could mean something else. Either way, this represents a change for you and it is best to consult your doctor for a thorough exam. Often, the bruising is innocuous, but is is best to be vigilant.

Possibly varicose: Veins or petechiae/purpura - small bleeding of tiny veins, could be contributed by low platelets or Aspirin intake. If it worsens, go see your dr.

Spider veins: Likely it is spider veins. It could be related to heredity, occupations that involve a lot of standing, obesity, hormonal influences during pregnancy, puberty, and menopause, birth control pills, a history of blood clots, conditions that cause increased pressure in the abdomen including tumors, constipation, etc. Tx varies from stocking compression, lifestyle changes-weight loss, laser, surgery etc.