Urine foam for a long time may be caused by nephritis, nephrotic syndrome, urethritis disease. 1. Nephritis: is caused by a variety of reasons for the renal tubules and the surrounding tissue inflammatory lesions, clinical manifestations and often overlap, often edema, hypertension, hematuria, proteinuria and so on. Increased urinary protein will lead to foam floating on top of the urine, and long lasting. 2. Nephrotic syndrome: it is a clinical syndrome caused by various renal diseases, characterized by massive proteinuria, hypoproteinemia, edema, and hyperlipidemia. Increased urinary protein will lead to foam floating on top of the urine and will not dissipate for a long time. 3. Urethritis: Urethritis is an inflammation of the urethra caused by bacterial infection, which can lead to an increase in urethral secretions such as immune proteins or other secretions, leading to more protein in the urine, triggering the phenomenon of long-lasting urine foam. Urine foam may also be seen in other kidney diseases such as diabetic nephropathy, nephrotic syndrome, etc. If the symptoms of urine foam do not dissipate and continue to be unrelieved, it is necessary to go to the regular hospital in time for medical treatment.