Can Protein in Urine Indicate Kidney Disease

Our kidneys are responsible for filtering blood and approximately 180L blood is filtered by glomeruli. For the glomerular barrier function, the macromolecular protein can not pass through glomeruli. Even if a small amount of protein and micromolecule protein pass thorough glomeruli, they will be reabsorbed by renal tubule. Therefore, only a small amount of protein(less than 150 mg) can be discharged into urine per day. Clinical tests show negative result. When more protein is excreted into urine, it is called proteinuria.

Protein in urine is a common symptom of Kidney Disease, but not all cases are caused by disease. In some stress situations like intensive exercise, under high temperature, undergoing operation and so on, there may be protein in urine of the healthy people. If stimulating factors are removed, their protein in urine will disappear afterwards. This belongs to biological protein in urine and it does not need treatment.

Pathological protein in urine is caused by glomerular diseases or other systemic diseases that influence the normal renal function. Pathological protein in urine can be divided into 4 types:

1. Protein in urine caused by primary or secondary glomerular diseases. The glomeruli are impaired so their barrier function is impaired and can not prevent protein leakage into urine.

2. Protein in urine is attributed to tubular damage. When the renal tubule is damaged, they can not reabsorb the protein that filtered by glomeruli. Another case is that the renal tubule secretes more protein, which also can lead to protein in urine.

3. In some cases, too much protein is produced in plasma so they are filtered out by glomeruli. The protein in filtrate surpasses the reabsorption ability of renal tubule so the excess protein will leak into urine.

4. Protein in urine is caused by abnormal renal hemodynamics. With the increasing of renal blood flow, the change in renal capillary transmembrane hydrostatic pressure can influence the glomerular filtration function and lead to temporary protein in urine.


As there are various kinds of causes of protein in urine, you should find its specific cause primarily before receiving relative treatment.