Casts
Casts are cylindrical proteinaceous formations that represent molds of the renal tubules, formed from protein and cellular debris under changing physicochemical conditions of urine. Their detection in urine is called cylindruria and is an important diagnostic sign of kidney diseases.
Main types of casts and their significance:
- Hyaline casts – composed of protein (tubular protein), may be found in small amounts in healthy individuals, especially after physical exertion. Increased amounts indicate proteinuria and early kidney damage.
- Granular casts – formed from destroyed epithelial cells of the renal tubules and protein masses. Indicate more pronounced kidney tissue damage.
- Waxy casts – dense, homogeneous, formed from hyaline or granular casts during prolonged urine stasis in tubules. Indicate severe chronic kidney diseases with marked tissue destruction.
- Erythrocyte casts – contain red blood cells, appear in glomerulonephritis and other diseases with glomerular damage and kidney bleeding.
- Leukocyte casts – contain white blood cells, characteristic of inflammatory kidney diseases such as pyelonephritis.
- Epithelial casts – composed of renal epithelial cells, indicate tubular damage due to toxic or ischemic injury.
Detection of casts in urine requires consultation with a nephrologist or therapist to identify the cause and prescribe treatment. Casts are absent or present in minimal amounts in normal urine. Their appearance is associated with kidney diseases, severe intoxications, systemic diseases, and acute transplant rejection reactions.
Diagnosis of cylindruria is performed by microscopic examination of urine sediment, often using centrifugation. The quantity and type of casts help assess the degree and nature of kidney damage, as well as the prognosis of the disease.