Complications of lower extremity venography include bleeding at the puncture site, allergic reactions and renal damage, and vascular injury. 1. Bleeding from puncture site: Lower extremity venography often requires puncture, which may cause bleeding ecchymosis, hematoma and other conditions. 2. Allergic reaction and kidney damage: Lower extremity venography requires the use of contrast medium, and some patients may have allergic reaction to the contrast medium, such as skin itching, hives and other reactions in mild cases, and in severe cases, it may even lead to anaphylactic shock. At the same time, the contrast agent needs to be excreted through the kidneys, and those with renal insufficiency may increase the load on the kidneys, which may cause some damage to the kidneys. 3. Vascular damage: Lower extremity venography is done with the assistance of guidewire and catheter, which may affect the function of vascular valves or cause some damage to the vascular wall, and then may cause thrombosis, etc. Angiography is commonly used in clinical practice. Angiography is one of the commonly used means of examination in the clinic, due to the invasive operation, there may be certain adverse reactions, but usually as long as the operation is carried out under standardized operating procedures, the occurrence of complications can generally be reduced.