Often people have edema in the ankle area, and the indentation can be seen by pressing, especially after prolonged sitting and standing in a car, it will become more obvious, so how is edema caused? The most common cause of edema is kidney-related diseases, such as nephrotic syndrome, chronic nephritis and renal failure, which can be clearly diagnosed by checking urine routine and kidney function. The second is due to cardiac insufficiency, which causes stasis in the body circulation. This condition is common in the elderly, or in patients with congenital heart disease, and some rare causes include lower limb thrombosis, hypothyroidism, venous valve insufficiency, etc. The presence of edema requires consultation with a nephrologist to clarify the cause and treat the symptoms.