The swelling of the legs even after the conversion of urine protein may be related to hypoproteinemia, decreased glomerular filtration rate and activation of the renin-angiotensin-aldosterone system. 1. Hypoproteinemia: urinary protein is lost from the urine, hypoproteinemia occurs, and plasma colloid osmolality is lower than normal. After the urine protein turns negative, it takes some time for hypoproteinemia to recover, and the patient still shows edema. 2. Decrease in glomerular filtration rate: abnormal glomerular filtration and reabsorption function, sodium retention will also be manifested as edema. 3. Activation of renin-angiotensin-aldosterone system: renal hypoperfusion activates this system, leading to vascular smooth muscle contraction and sodium retention, causing leg swelling. If your legs are still swollen even after the urine protein has become negative, you should go to the hospital in time to have the cause clarified under the guidance of a professional doctor, and then have the symptomatic treatment.