Causes of proteinuria

When a disease occurs in the human body, it will also cause various problems in the body. Therefore, the treatment of the disease needs to be carried out in a timely manner. Many people do not understand proteinuria. It is an important element of the human body. Its abnormality is very harmful to human health. Moreover, its abnormality is also caused by the disease. Therefore, when the proteinuria is low during the examination, it is necessary to understand the cause of proteinuria.

Many people are not very clear about low proteinuria, so they can also consult in detail on this issue, so that they can have a good understanding of such problems and know how to improve them best. So what is the cause of proteinuria?

Causes of proteinuria:

1. Classification by the mechanism of proteinuria

Renal proteinuria

1. Glomerular proteinuria, whether primary or secondary to glomerular damage, is the most common protein in clinical practice. There are lesions in the glomerular filtration membrane, the basement membrane is thickened, the pores are enlarged, the protein leakage increases, and even globulins with larger molecular weight may leak out. It is seen in acute glomerulonephritis, various types of chronic glomerulonephritis, IgA nephritis, and latent nephritis. Secondary disease is seen in autoimmune diseases such as lupus nephritis, diabetic nephropathy, purpuric nephritis, renal artery sclerosis, etc. Metabolic diseases are seen in gouty kidney.

2. Tubular proteinuria refers to normal glomerular filtration and tubular reabsorption disorder. The most common causes are interstitial nephritis, renal vein thrombosis, renal artery embolism, heavy metal salt poisoning, etc. The amount of this type of urine protein is less than the amount of glomerular protein.

3. Renal tissue proteinuria is also called secretory proteinuria. Both the glomerular filtration function and the tubular reabsorption function are normal. This is because during the formation of urine, proteins produced by tubular metabolism infiltrate into the urine, such as the Tamm-Horsfall protein produced by the tubular mixing with the distal tubular protein (a large molecular glycoprotein). This protein is easy to form casts and stone cores.

Non-renal proteinuria

1. Humoral proteinuria is also called overflow proteinuria. Both the glomerular filtration function and the tubular reabsorption function are normal. This is because the plasma contains a large amount of small molecule protein that is filtered by the glomerulus, which exceeds the reabsorption capacity of the tubules. For example, in multiple myeloma, a large amount of light chain immunoglobulin in the plasma is excreted from the urine, which is called gelatin or Benee None protein. When the urine is heated to 45-60°C, the gelatin begins to coagulate and the urine becomes turbid. When it is further heated to the boiling point, it dissolves. The urine becomes clear, and when it is cooled to below 60°C, turbidity, precipitation or clots appear again. This test is the most commonly used method for diagnosing multiple myeloma. Furthermore, bone X-rays should be taken at multiple locations to detect bone destruction (mostly in the skull, ribs, spine, etc.) and a bone marrow examination should be performed. A large number of myeloma cells can be found, which is an important basis for diagnosis.

2. Tissue proteinuria: Proteins produced by some organs and tissues are filtered out by the glomeruli through the blood circulation and excreted in the urine, such as proteins in the urine of malignant tumors and host proteins produced by viral infections.

3. Proteinuria caused by the mixing of lower urinary tract protein into urine is seen in urinary tract infection, urinary tract epithelial cell shedding and urinary tract mucin secretion.

2. According to the nature of proteinuria

1. Functional proteinuria

It is a mild benign proteinuria, which disappears quickly after the cause is eliminated. The 24-hour urine protein quantity generally does not exceed 0.5g. Its production mechanism is still unclear. It may be caused by internal and external factors affecting the kidneys, causing renal vasospasm, congestion, and increased glomerular filtration rate. It is seen in strenuous exercise, long-distance marches, and high temperature environments. Fever, severe cold environment, mental stress, congestive heart failure, etc.

2. Pathological proteinuria

It is the most common and important proteinuria, seen in primary or secondary kidney diseases. Generally, the amount of urine protein is high, and the urine sediment contains red blood cells, white blood cells, camptothecin, edema, hypertension and other clinical manifestations.

3. Postural proteinuria

Its characteristic is that the appearance of proteinuria is related to body posture, such as long-term standing, walking, and lordosis of the spine. Postural proteinuria is caused by temporary circulatory disorder due to twisted renal vein or lordotic spine compressing the left renal vein. The urine protein disappears or decreases after one hour of lying down. When postural proteinuria is suspected, measuring the amount of protein in the urine before and after getting up in the morning may show a significant difference. If it is caused by lordosis, ask the patient to stand with his back against a wall for 10 minutes and then observe. If protein in the urine appears, the diagnosis can be confirmed. The diagnosis of orthostatic proteinuria should be made with caution and requires long-term follow-up, generally more than 5 years of observation, and a diagnosis can only be made if the condition remains unchanged and renal function remains normal. Once persistent proteinuria and functional impairment are detected, the diagnosis should be corrected and treatment measures should be taken promptly.

Through the above introduction, we have some understanding of the causes of proteinuria. When problems occur, we can compare them according to the above. If the physical problem is very serious, it is necessary to treat it in time, otherwise it will cause other diseases in all aspects of the body and pose a threat to one's life.