The most likely cause of foot swelling is venous valve insufficiency in the lower extremities. In this case, you should go to the vascular surgery department as soon as possible and have an ultrasound examination, through which you can determine whether there is venous valve insufficiency in the lower extremities and the degree of incomplete closure. After the diagnosis is clear, conservative treatment can be carried out by using elastic medical stockings and taking oral medication such as Avalanche or Mizarin, which can usually achieve very good results.