Cast urine

Introduction The tube type is an important component in urine sediment, and the appearance of tube type urine often indicates substantial damage to the kidney. A cylinder formed by the aggregation of proteins in the renal tubules. Normal people should have less than 5,000 urinary tube types in 12 hours, 2 to 5 in each milliliter of urine, or less than 1 in each low-power field. The increase in the type of tube in the urine is called tubular urine, and the appearance of tubular urine often indicates substantial damage to the kidney.

Cause

Protein secreted by renal tubular epithelial cells forms a transparent cast due to concentration and coagulation in an acidic environment. If accompanied by red and white blood cell agglomeration, it is called cell tube type. If there is degenerative cell debris, a granular cast is formed. If the tubular matrix contains fat droplets or embedded in epithelial cells containing fatty degeneration, it forms a fat tube type, which is an important component in urine sediment, and its appearance often indicates substantial damage to the kidney. It is a cylindrical structure formed by solidification of proteins in the urine in the renal tubules and collecting ducts. The formation of the casts requires proteinuria, and the matrix formed is a TH glycoprotein. In 1966, Mcqueen further confirmed by fluorescent antibody method that various proteins of different molecular weights in plasma can be aggregated in a transparent tubular matrix (TH glycoprotein) in the form of particles. In the pathological condition, due to the increased permeability of the glomerular basement membrane, a large amount of protein enters the renal tubule from the glomerulus, and in the renal distal convoluted tubule and collecting duct, acidification (increased acidity) and cartilage due to concentration (water absorption) In the presence of sulphate, the protein condenses and precipitates in the renal tubules to form a cast.

an examination

Related inspection

Urine sediment type inspection urine sediment type

The clinical significance of various tube types is as follows:

(1) Cell tube type:

1 The red blood cell cast is pathological, indicating that the source of hematuria is in the renal tubule or glomerulus, which is common in acute glomerulonephritis, acute pyelonephritis or acute renal failure.

2 white blood cell cast is pathological, is an important evidence for the diagnosis of pyelonephritis and interstitial nephritis. If there are more such tube types in the urine, it has more diagnostic value and can be used as a basis for distinguishing pyelonephritis and lower urinary tract infection.

3 Epithelial cell casts appear in large amounts in the urine, indicating that the renal tubules have active lesions. This condition can occur in glomerulonephritis, often coexisting with granules, clear or red, and white blood cell casts.

(2) Granular tube type: The granular tube type is derived from the epithelial cell cast type or formed by the protoplasmic adhesion of the disintegrated epithelial cells. The granular tube type means that there is degeneration and necrosis of renal tubular epithelial cells at the same time as proteinuria, which is more common in various glomerular diseases and toxic damage of renal tubules. Sometimes it can also occur in normal human urine, especially after strenuous exercise, if it is repeated frequently, it is abnormal.

(3) Wax-like and fat-tube type: wax-like and fat-tube type are formed after the cell granules are degraded again, often reflecting the atrophy and expansion of the renal tubules. More common in chronic kidney disease with reduced urine output, or in the presence of fatty disease in nephrotic syndrome.

(4) Transparent tube type: The transparent tube type can appear in normal urine, and the transparent tube type will increase when there is proteinuria, which is found in various glomerular diseases.

Differential diagnosis

Protein secreted by renal tubular epithelial cells forms a transparent cast due to concentration and coagulation in an acidic environment. If accompanied by red and white blood cell agglomeration, it is called cell tube type. If there is degenerative cell debris, a granular cast is formed. A fat tube type is formed if the tubular matrix contains fat droplets or is embedded in epithelial cells containing fatty degeneration. Increased granules in the urine often indicate damage to the renal parenchyma.

The tubular urine is a cylindrical structure formed by solidification of proteins in the urine in the renal tubules and collecting ducts. The formation of the tubular type requires proteinuria, and the matrix formed is a TH glycoprotein. In the pathological condition, due to the increased permeability of the glomerular basement membrane, a large amount of protein enters the renal tubule from the glomerulus, and in the renal distal convoluted tubule and collecting duct, acidification (increased acidity) and cartilage due to concentration (water absorption) In the presence of sulphate, the protein condenses and precipitates in the renal tubules to form a cast.

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