The most common cause of sudden swelling of the feet is kidney disease, such as glomerulonephritis, nephrotic syndrome and renal failure. When suffering from glomerulonephritis, there will be water and sodium retention, causing swollen feet. At this time, urine routine and blood albumin, creatinine and urea can be checked to clarify the diagnosis. In addition to kidney disease, cardiac insufficiency can also cause swollen feet. In right heart failure, there will be stasis of blood in the body circulation, mainly manifesting as lower limb edema, with swollen feet being the most common, which can be clearly diagnosed by examining cardiac ultrasound. When sitting and standing for a long time, the blood circulation in the lower extremities will also be poor, mainly due to poor venous return, causing swelling of the feet, which can be treated with diuretics. For example, nephrotic syndrome requires hormone and immunosuppressant treatment, while cardiac insufficiency requires cardiotonic and diuretic drugs to improve cardiac function.