Thigh swelling after patent foramen ovale surgery may firstly be caused by postoperative complications, such as lower extremity deep vein thrombosis, and secondly, it may also be caused by hypoproteinemia, nephrotic syndrome and other diseases. 1. Lower extremity deep vein thrombosis: patients with unclosed foramen ovale will be intervened through femoral vein puncture, and patients are prone to femoral vein thrombosis complications during femoral vein puncture. If the patient has femoral vein thrombosis, it will be manifested as swelling of the affected limb, skin bruising and tension blisters, so the patient will have thigh swelling after the patent foramen ovale. 2. Hypoproteinemia: If patients have insufficient protein intake or protein synthesis disorder after foramen ovale surgery, it may lead to edema, ascites, pleural effusion, so some patients may have symptoms of thigh swelling. 3. Nephrotic syndrome: patients with nephrotic syndrome after surgery for patent foramen ovale will have a large amount of proteinuria, edema, weight gain and other manifestations, so that some patients will be manifested as post-surgical thigh swelling. It is recommended that patients with postoperative thigh swelling need to consult a doctor in a timely manner, and can choose appropriate measures for treatment under the guidance of the doctor.