What causes white liquid in male urine?

When men urinate, white liquid often appears. This liquid is called proteinuria. Proteinuria includes normal physiological proteinuria and this type of proteinuria is mainly caused by physical reasons such as fever and tension. There is also pathological proteinuria, such as glomerular proteinuria, tubular proteinuria, overflow proteinuria, secretory proteinuria, tissue proteinuria, mixed proteinuria, etc.

1. Physiological proteinuria

There is no organic lesion, which is common in the following two situations:

1. Functional proteinuria is transient proteinuria caused by stressful conditions such as strenuous exercise, fever, tension, etc. It is more common in adolescents. The urine protein in qualitative tests usually does not exceed (+).

2. Postural proteinuria is common in adolescents during puberty. Proteinuria occurs in the upright and lordotic postures and disappears in the supine position. The general protein excretion is <1g/d.

2. Glomerular proteinuria

Proteinuria is caused by damage to the glomerular filtration membrane, increased permeability, and plasma protein filtration that exceeds the reabsorption capacity of the renal tubules. The most common proteinuria clinically is more common in primary or secondary glomerular diseases, such as acute nephritis, rapidly progressive nephritis, chronic nephritis, IgA nephropathy, nephrotic syndrome, lupus nephritis, purpuric nephritis, diabetic nephropathy, hypertensive nephropathy, tumor nephropathy, renal amyloidosis, toxic nephropathy and renal damage caused by infection. It is also seen in congenital nephritis, renal circulation disorders, renal hypoxia, accelerated renal blood flow, etc.

3. Tubular proteinuria

When the structure or function of the renal tubules is damaged, the renal tubules are unable to reabsorb normally filtered small molecular weight proteins, resulting in protein excretion in the urine, which is called tubular proteinuria. It is common in tubular-interstitial lesions caused by various reasons, such as pyelonephritis, interstitial nephritis, reflux nephropathy, uric acid nephropathy, renal tubular acidosis, heavy metal poisoning, Fanconi syndrome, hypokalemic nephropathy, renal medullary cystic degeneration, radiation nephritis, analgesic nephropathy, rejection reaction after renal transplantation, etc.

4. Overflow proteinuria

Proteinuria is caused by an abnormal increase in small molecular weight proteins in the blood, such as multiple myeloma light chain protein, hemoglobin, myoglobin, etc., which are filtered out from the glomeruli and exceed the threshold of tubular reabsorption. All of it can be reabsorbed by the renal tubules. Bence Jones protein is common in multiple myeloma, and is also seen in macroglobulinemia, heavy chain disease and light chain disease, amyloidosis, and occasionally in monocytic leukemia; hemoglobin or myoglobin is seen in massive muscle tissue damage, excessive hemolysis, etc.; rejection of transplanted kidney and diffuse intravascular coagulation, increased FDP in urine are also overflow proteinuria.

5. Secretory proteinuria

Proteinuria is caused by protein secreted by the renal tubules and lower urinary tract or other proteins that infiltrate into the urine. Related to immune response and urinary tract infection.

6. Tissue proteinuria

It mainly refers to some soluble tissue decomposition metabolites secreted by kidney tissue, and structural proteins released by kidney and urinary tract tissue necrosis in pathological conditions such as poisoning, ischemia, inflammation or tumor. For example, in case of glomerulonephritis, glomerular basement membrane antigens, tubular brush border antigens and various enzymes are excreted in the urine; in case of tumors, specific antigenic substances related to the tumor can be detected in the urine.

7. Mixed proteinuria

Clinically, when two types of proteinuria, such as glomerular proteinuria and tubular proteinuria, coexist, it is called mixed proteinuria. Glomerulonephritis can affect both the glomeruli and tubules, resulting in glomerular and tubular proteinuria. Mixed proteinuria is also common in chronic renal failure.