Typically varicose veins will extend down the length of the vein or other branches rather than popping. If, however, the vein wall and surrounding skin becomes very thin they can rupture. Some people say they experience a "popping" sensation which may be when the small valves fail under pressure from above. It is hard to speculate what exactly causes this.
Varicose veins can rupture spontaneously, usually happening in the shower while bathing. This is the result of increased venous pressure and progressive thinning of the vein wall. This complication can be very frightening to the patient and frequently ends up in the ER. If this ever happens to you, apply finger pressure at the bleeding point, elevate the leg to the vertical position and apply a compression bandage, and seek medical attention. The compression bandage will prevent further bleeding. Go to the ER only if you lose more than a cups of blood or if the bleeding does not stop.
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