Unilateral lower limb edema is a relatively common clinical symptom. Generally speaking, there are several common causes as follows: i. Dermatitis, Dermatitis is an acute infection of the lymphatic vessels of the skin, mostly seen in patients with footrot or local skin breakdown, where bacteria invade the lymphatic vessels along the skin breakdown, causing acute inflammatory manifestations. Patients will have obvious symptoms such as swelling and pain in the lower limbs, generally speaking, patients can recover after 2-3 weeks with active anti-infection treatment. Second, the formation of deep vein thrombosis in the lower extremity, the most common ones, such as femoral vein and popliteal vein thrombosis, will cause the obstruction of blood return to the lower extremity, so that more venous blood will accumulate in the lower extremity, causing unilateral limb swelling. Patients can have ultrasound ultrasound examination to clarify the cause, and at the same time actively anticoagulation treatment to avoid serious complications caused by thrombus dislodgement. Third, local lymphatic vessel blockage, such as lymphadenoma and enlarged lymph nodes in the groin area compressing lymphatic vessels can cause lymphatic vessel reflux obstruction, resulting in lower limb swelling.