Proteinuria is the Typical Symptom of CKD

We know that protein is the material basis for maintaining human life and normal daily activities. Protein accounts for 16%-20% of body weight and it participates in the formation of each cell and all important parts.

Under normal circumstances, there is no or very small amount of protein (less than 150mg/d) leaked in uirne which are small-molecular proteins. It is negative in urinary protein qualitative test. If protein in urine increases and is detected in routine urine test, it is called proteinuria in clinic. It is massive proteinuria if urinary proteins exceed 3.5g/24h which is the typical symptom and sign of nephrotic syndrome.

Proteinuria is the typical symptom of chronic kidney disease and its formation has close relation with barrier function of the glomeruli and re-absorption ability of the tubules.

When kidneys are impaired by various pathological damages (including primary and secondary ones), the micro-circulation in the kidneys will be disturbed and renal tissues will suffer from ischemia and hypoxia. Lack of blood and oxygen supply will damage the glomerular capillary endothelial cells and infiltration of inflammatory medium. As a result, the gomerular filtration membrane and barrier functions will be damaged and large amount of protein will pass through it and proteinuria will occur.

Renal proteinuria can be sub-divided into glomerular proteinuria, tubular proteinuria and secretory proteinuria.

1. Glomerular proteinuria. It includes acute and chronic glomerulonephritis, IgA nephritis, latent nephritis, diabetic nephropathy, purpura nephritis, lupus nephritis, renal atherosclerosis, hyperuricemia nephropathy, etc.

2. Tubular proteinuria. It is more common in cases of interstitial nephritis, renal vein thrombosis, renal artery embolization, heavy mental poisoning, etc.

3. Secretory proteinuria. This is due to protein being mixed with urine during the formation urine and the protein comes from renal tubular metabolism.

Of cause, not all proteinuria case is definitely related to kidney diseases and it can be caused by other diseases such as multiple myeloma, infections in urinary system, etc.