[Blood groups as a risk factor in venous thrombosis]. / Los grupos sanguíneos como factor de riesgo en las trombosis venosas.

We report 173 patients with venous thrombosis (or post-thrombotic syndrome) demonstrated by phlebography. We show up the importance of blood groups as risk factor, being very significant the A group. Female sex is associated with a high incidence of this pathology. A frequent location is the left lower limb.