Swollen veins might be a symptom of a person whose vein valves are not functioning properly and are causing fluid it flow away from the heart.
Explanation;
Valves are structures that are found in the circulatory system both in the heart and the veins.
They function to prevent the back flow of blood.
They do so by ensuring the continuous flow of blood in one direction.
If the valves are not functioning properly it may lead to various effects such as swollen veins due to the back flow of blood which may lead to the pooling of blood in the extremities.