The causes of swollen feet after sitting for a long time include physiological factors (prolonged sitting, prolonged sagging of the legs) and pathological factors (varicose veins, kidney disease, etc.), which need to be analyzed specifically. 1. Physiological factors: prolonged sitting, sagging lower limbs, gravity will lead to lower limb venous blood and lymphatic fluid reflux obstruction, resulting in increased exudation in the interstitial space of tissues; at the same time, prolonged sitting activities reduce the contraction of muscles, the deep veins of the lower limbs lose the role of the muscles on its extrusion, resulting in slow blood flow, easy to appear swelling of the lower limbs. 2. Pathological factors: varicose veins, due to structural and functional abnormalities of the veins of the lower limbs, lead to obstruction of venous blood return, and swelling of the lower limbs is easy to appear, and ultrasound of the veins of the lower limbs can assist in the clear diagnosis. Kidney disease, such as nephritis, nephrotic syndrome, etc., glomerular filtration rate decrease leads to sodium retention or plasma colloid osmotic pressure decrease easily caused by swelling of the lower limbs, renal function, renal biopsy and puncture can assist in the definitive diagnosis. Sitting for a long time feet swelling can be relieved by appropriate activities, reduce sedentary, such as the situation is not relieved or gradually aggravated, it is recommended to go to the hospital as soon as possible, a clear diagnosis, timely treatment, to avoid delays in the condition.