Proteinuria

Introduction When the protein content in the urine increases, regular urine examination can be measured, called proteinuria. If the urine protein content is 3.5g / 24h, it is called a large amount of proteinuria. Under normal circumstances, due to the filtration of glomerular filtration membrane and the reabsorption of renal tubules, the amount of protein in the urine of healthy people (multiple molecular weight proteins) is very small (less than 150 mg per day) ), when the protein is qualitatively tested, it is negative. In pathological conditions, such as with kidney disease, the filtration of the filtration membrane changes. One of the typical diagnostic criteria for chronic nephritis, purpuric nephritis, lupus nephritis, and diabetic nephropathy is the abnormality of proteinuria and hematuria at the time of routine urine examination, and is highly suspected of kidney disease. There is very little protein in normal urine, no more than 7~10mg/24h, which can not be detected by ordinary urine routine examination. Breakage, damage to the charge barrier, increased renal permeability, and a decrease or loss of negatively charged glycoproteins on the membrane may result in a significant increase in negatively charged plasma protein filtration over normal. Therefore, proteinuria is formed clinically in this period.

Cause

(a) renal proteinuria

Glomerular proteinuria

Found in acute glomerulonephritis, various types of chronic glomerulonephritis, IgA nephritis, occult nephritis.

Secondary findings in autoimmune diseases such as lupus kidney, diabetic nephropathy, purpuric nephritis, renal arteriosclerosis, etc. Proteinuria metabolic disorders are seen in gout kidneys.

There are two types according to the extent of lesion damage and proteinuria:

1 Selective proteinuria: mainly albumin, with a small amount of small molecular weight protein, no large molecular weight protein in urine (IgG, IgA, IgM, C3, C4), semi-quantitative in +++ ~ +++ +, the typical disease is nephrotic syndrome.

2 non-selective proteinuria: indicates that the glomerular capillary wall has severe damage and breakage, and there are large molecular weight proteins in the urine, such as immunoglobulin and complement. Medium molecular weight albumin and small molecular weight protein, urine protein, immunoglobulin/albumin ratio >0.5, semi-quantitative is +~++++, quantitatively between 0.5-3.0g/24h, more common in primary Glomerular diseases, such as acute nephritis, chronic nephritis, membranous or membrane proliferative nephritis, and secondary glomerular diseases, such as diabetic nephritis, lupus nephritis. The presence of non-selective proteinuria suggests a poor prognosis.

Proteinuria can also occur in strenuous exercise, long-distance marching, high temperature environment, fever, cold environment, nervousness, congestive heart failure, etc.

2. Renal tubular proteinuria

The most common causes of interstitial nephritis, renal vein thrombosis, renal artery embolism, heavy metal salt poisoning.

3. Renal tissue proteinuria

Also known as secreted proteinuria. Due to the infiltration of proteins produced by tubular metabolism into the urine during urine formation.

(two) non-renal proteinuria

Humoral proteinuria

Also known as spilled proteinuria, such as multiple myeloma.

2. Tissue proteinuria

Such as malignant tumor protein in urine, host protein produced by viral infection, and the like.

3. Lower urinary tract protein mixed into the urine causes proteinuria

Found in urinary tract infections, urinary tract epithelial cell shedding and urinary tract secretion of mucin.

an examination

Related inspection

Protein electrophoresis

(1) medical history

According to the reasons of proteinuria, different medical history should be emphasized, such as history of edema, occurrence of hypertension, history of diabetes, history of allergic purple epilepsy, history of drug use in damaged kidneys, history of heavy metal salt poisoning, history of connective tissue disease, metabolism History of illness and gout.

(2) Physical examination

Pay attention to edema and serous effusion, bone and joint examination, degree of anemia and examination of heart, liver and kidney signs. Fundus examination, normal nephritis, normal or mild vasospasm, chronic nephritis, fundus arteriosclerosis, hemorrhage, exudation, etc. Diabetic nephropathy often has diabetic fundus.

(3) Laboratory inspection

Urine protein examination can be divided into qualitative, quantitative and special examinations.

1. Qualitative examination: It is best to have morning urine, morning urine is the strongest, and orthostatic proteinuria can be ruled out. Qualitative examination is only screening and screening. The daily urine volume of 2000ml is qualitatively "+' of urine protein is more than the urine volume of 400ml as "+', so it is not an accurate indicator of urine protein content. The diagnosis of kidney disease, the observation of the condition, and the determination of the curative effect should be based on the quantitative determination of urine protein.

2. Quantitative examination of urine protein: There are many methods, such as Pap test, double porpoise method, phosphotungstic acid method, acid reading, ferric chloride method, etc., which is the most accurate and most commonly used. 24h urine protein 1g less glomerular disease opportunities, common causes of pyelonephritis, renal cirrhosis, urinary tract obstruction, urinary tract tumors and stones. The most common cause of urinary protein 1~3g is primary or secondary glomerular disease. 24h urine protein quantitation above 3.5g is seen in primary or secondary nephrotic syndrome.

(4) Urine eggs from special inspection

Commonly used urine protein electrophoresis examination can distinguish between selective proteinuria and non-selective proteinuria. Urine protein electrophoresis examination of multiple myeloma is helpful for typing, and can be divided into the following five types: chat. IgG, IgA, IgE, IgD type. The urine radioimmunoassay method is a qualitative method for urine protein. When the urine routine is negative, the radioimmunoassay can be positive, and the false positive rate of the defect is high. Radioimmunoassay urinary 2-mg determination is helpful for the diagnosis of early renal tubular dysfunction.

Differential diagnosis

It should be differentiated from the following symptoms:

1. Edema with proteinuria: edema with severe proteinuria is mostly renal edema. Mild proteinuria can also be seen in cardiogenic edema in addition to nephrotic edema. Edema during pregnancy, proteinuria is more common in gestational poisoning edema.

2. Pregnancy proteinuria: Generally speaking, the protein in normal urine is very small, no more than 7~10mg/24h, which can not be detected by ordinary urine routine examination. In fetal urine, when the protein content in the urine increases, regular urine examination can be measured, called fetal proteinuria. If the urine protein content is 3.5g / 24h, it is called a large amount of proteinuria.

3. Hematuria with proteinuria: Renal hematuria refers to hematuria derived from glomeruli, clinical manifestations of simple hematuria, or hematuria with proteinuria. If the treatment is not thorough, repeated attacks or treatment failure, the condition can not be effectively controlled, and eventually lead to uremia.

4. Low-molecular proteinuria: Low-molecular proteinuria is caused by damage to the tubular function of the renal glomerulus, which causes the protein that has been filtered through the normal glomerulus to reabsorb.

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