We normally see varicose veins and spider veins in the calves and thighs. Hidden varicose veins can also occur in the pelvic area. The reason is simple. Blood has to travel the farthest away from the heart to reach the feet. On its return to the heart, blood must flow upward against gravity. As a consequence, the veins in the legs tend to experience more pressure than veins elsewhere in the body. Under circumstances that increase pressure or weaken the veins, chronic insufficiency can develop.