Urine Casts

Hyaline

● Most commonly encountered & most difficult cast to discover.

● Colorless, transparent, homogenous cylinders with smooth edges; often difficult to detect due to low refractive index.

Non-pathologic

Hyaline appears after strenuous exercise, dehydration, fever, or stress.

Pathologic

Hyaline increases in numbers seen in glomerulonephritis, pyelonephritis, chronic renal diseases, and congestive heart failure

RBC Cast

● Cylindrical casts containing intact or fragmented RBCs, giving a yellow to brown appearance; often granular as cells degenerate.

● Most diagnostic type of cast; may break down easily, so careful examination is needed.

● Strongly indicates bleeding within the nephron.

● Seen in glomerulonephritis, vasculitis, malignant hypertension, and strenuous exercise.

Blood Cast (Muddy Brown Cast)

● Appears as brown to muddy brown, pigmented casts without intact RBCs; color results from the incorporation of hemoglobin or myoglobin into the cast matrix.

● Formed when RBCs lyse within the tubules, releasing hemoglobin, or when myoglobin is filtered due to muscle injury

● Seen on severe intravascular hemolysis (Hemolysis) or rhabdomyolysis (Myoglobinuria).

● May also appear in acute tubular necrosis due to pigment-induced tubular damage.

● Sometimes described as pigmented casts and distinguished from granular casts by their uniform brown coloration.

WBC Cast (Pus Cast)

● Cylindrical cast containing intact or degenerated WBCs; may appear granular as cells break down.

● Indicates inflammation or infection withing the nephron, differentiating upper urinary tract infections from lower tract infections.

● Commonly seen in pyelonephritis and acute interstitial nephritis (often drug-induced).

Renal Tubular Epithelial/Epithelium (RTE) Cast

● Cells visible on the cast matrix are small, round, oval cells.

● Cylindrical casts with embedded RTE Cells, which appear as small, round to oval cells within the protein matrix'; may show eccentric nuclei.

● Strongly indicates tubular injury or necrosis.

● Seen in Acute Tubular Necrosis (ATN), toxic drug reactions, viral infections (e.g., CMV, hepatitis), and heavy metal poisoning

● As the cell degenerate, they may form granular casts, progressing to waxy casts in chronic damage.

Bacterial Cast

● Casts containing bacteria embedded within the protein matrix, often accompanied by WBCs.

● May appear granular or dirty-looking under the microscope.

● Presence of bacteria within casts confirms renal infection, differentiating upper urinary tract infection (pyelonephritis) from lower tract infection.

Granular Cast

● Derived from the degeneration of renal tubular epithelial (RTE) cells and the breakdown of cellular casts or from the aggregation of plasma proteins and filtered serum proteins.

● Associated with glomerulonephritis, pyelonephritis, and other renal diseases involving tubular damage or proteinuria.

Finely Granular Cast

Sandpaper-like appearance, often difficult to distinguish from hyaline casts.

Coarsely Granular Cast

Larger granules, representing further degeneration of cells or proteins.

Fatty Cast

● Contain lipid droplets or oval fat bodies embedded in the protein matrix.

● Strongly associated with Nephrotic Syndrome.

● Seen in nephrotic syndrome, diabetes mellitus, toxic tubular necrosis, lupus nephritis, and other disorders causing heavy proteinuria and lipid loss.

● Lipid content can be confirmed with Polarizing microscopy or lipid stains.

Waxy Cast

● Represent the FINAL STAGE OF DEGENERATION OF GRANULAR AND CELLULAR CASTS.

● Brittle, highly refractile, with jagged or notched edges and cracks; appear as ground glass under the microscope.

● Seen in chronic renal failure, severe long-standing renal disease, malignant hypertension, and renal amyloidosis.

● Considered a poor prognostic sign indicating prolonged stasis of urine flow within damages tubules.

Broad Cast (Renal Failure Cast)

● Much wider than other casts, reflecting formation in dilated or atrophic collecting ducts.

● May appear hyaline, granular, waxy, or cellular, depending on the composition.

● Indicates destruction and widening of tubular walls, most often seen in renal failure and advanced chronic kidney failure.