Usually, the clinical term for venous thrombosis in the lower extremities is venous thrombosis, which is mainly characterized by swelling and pain in the affected limb, with symptoms worsening after activity. Mild bruising of the affected limb at the ankle, or severe bruising, may improve with elevation of the affected limb. In addition, the patient may develop fever and itchy skin if there is a lack of nutrients in the limb due to prolonged thrombosis. If the thrombus is present in the deep iliac-femoral vein, edema may be evident at the belly of the leg, and the skin at the belly of the leg may turn white because the pressure in the tissue is greater than the intravascular perfusion pressure. Pain in the medial hip, swelling of the affected limb, palpable striae, accompanied by a feeling of tenderness, may be accompanied by systemic symptoms such as fever and chills, also known as central deep vein thrombosis. If the symptoms of thrombosis continue to extend to the whole venous system, the skin of the affected limb may appear tight and shiny, and the superficial veins may be visible to the naked eye as protruding from the epidermis and varicose, which may be accompanied by recurrent venous ulcers of the lower limbs in severe cases. If the thrombus is inadvertently dislodged and travels to the lungs with the blood flow, it may cause pulmonary embolism, which is life-threatening. In addition, thrombus can also be formed in the visceral system and upper extremities, such as renal vein thrombosis, portal vein thrombosis, and upper extremity thrombosis, but the symptoms are not obvious, so it is rare and easily confused with other diseases. Renal vein thrombosis may appear as hematuria, accompanied by back discomfort, hypertension, and swelling of the face. Portal vein thrombosis, on the other hand, presents with persistent abdominal pain, abdominal distension, and gastrointestinal bleeding, accompanied by systemic symptoms such as fever and chills. Upper extremity thrombosis is usually seen in upper extremity trauma or tumor compressing the subclavian vein, which can be clinically seen as red, swollen and painful limbs.