What condition involves extended and twisted veins due to a lack of venous return?

The condition that involves extended and twisted veins due to a lack of venous return is varicose veins. This occurs when the one-way valves in the veins become weakened or damaged, resulting in blood pooling in the veins rather than being effectively returned to the heart. As the blood accumulates, the veins become enlarged and distorted, leading to the characteristic swollen, twisted appearance associated with varicose veins.

The other conditions do not involve the same mechanism of vein structural change or blood flow.

Phlebitis refers to inflammation of the veins, which can cause pain and swelling but does not inherently describe the twisting or elongation of the veins like varicose veins do. Aneurysms involve the abnormal bulging of a blood vessel wall, which is a different process altogether. Stenosis refers to the narrowing of a blood vessel, which would restrict blood flow but does not result in the twisting and expansion of veins as seen in varicose veins. Thus, the correct identification of varicose veins captures the key features of the condition described in the question.