Casts

The image below represents different casts seen in urine at the same magnification and lighting. Shown are hyaline, hyaline casts with adherent fat, granular and waxy casts.

Hyaline casts: These can be quite difficult to see in wet preparations of urine sediments with light microscopy, even with the condenser of the microscope racked down. They are much easier to visualize using phase contrast, however phase is usually not available on most microscopes. They become more visible with regular light microscopy if fat sticks to the protein matrix (Tamm-Horsfall mucoprotein) that makes up the hyaline cast (hyaline with fat) or particulate material from degenerating cells is present within the cast matrix (hyaline to finely granular cast).

Cellular casts: These have distinct cells within the protein matrix - if the cells are of epithelial origin (i.e., not WBCs or RBCs), they are called epithelial casts..

Granular casts: As cells within the protein cast matrix break down, the cast becomes coarsely then finely granular.

Waxy casts: Waxy casts are the final stage of cast degeneration (usually originating from cellular and granular casts). Compared to hyaline casts, they are readily observable because they have a smooth appearance, no internal texture, and are more refractile than the surrounding urine.

Of all these casts, hyaline (with or without adherent fat) and finely granular casts may be seen in urine from healthy animals. Cellular, coarsely granular and waxy casts always indicate renal pathology. For more information on the meaning of casts, view the routine urinalysis section.

cast compilation
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