Clinically, the so-called dilated veins are all visible to the naked eye, so the so-called dilated veins are all superficial venous dilatation. There are two main reasons for the formation of superficial venous dilatation: 1, it is due to the simple superficial veins, the superficial veins themselves have weak walls, venous valve insufficiency, and intravenous hypertension, resulting in poor venous return, which can cause the superficial veins to become tortuous and dilated, forming varicose vein-like changes; 2, it is the formation of deep vein thrombosis or deep vein embolism, resulting in the corresponding parts of the superficial veins The condition of tortuosity, dilatation, and establishment of collateral circulation to help the deep renal vein return. In this case, the superficial veins are compensated by thickening, tortuosity, and dilatation due to the obstruction of the return flow in the deep veins, creating varicose vein-like changes to help return the deep veins. Thus, the superficial veins are dilated for these two main reasons.