Swelling of the left foot may be a precursor to a blood clot or deep vein valve insufficiency of the lower extremity, and the two conditions can be treated separately. In the first case, the swelling of the left foot occurs suddenly, which often means that a thrombosis is likely, and this edema does not resolve with elevation of the affected limb or with rest and lying down. In the second case, the swelling occurs slowly and is relieved by rest and lying down, and is typically characterized by morning sickness, i.e., the symptoms are mildest in the morning and worst in the evening before bedtime. In most cases, this is due to increased oedema resulting from increased reflux of blood with upright movement in cases of venous valvular insufficiency in the lower limbs. A definitive diagnosis of these two conditions can be obtained by ultrasound, and staging and treatment is based on the clinical information obtained.