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Urinary Casts

What are Casts?

Urinary Casts are mainly transparent, cylindrical structures formed from the solidification of material within the lumen of the kidney tubules takes their long, thin, hollow shape. 

Pathological conditions that aid in the creation of casts include:

  • Presents of protein constituents in tubular urine

  • Increase urine acidity

  • Increase osmolar concentration

Major Casts Types

  • Hyaline

  • Epithelial

  • White Blood Cells

  • Red Blood Cells

  • Granular

    • Coarse​

    • Fine

  • Waxy

  • Fatty

Hyaline Casts

Appearance:

  • Transparent (clear), cylindrical

  • Have parallels sides with slightly rounded ends

Causes: 

  • Renal Proteinuria

    • Predominantly Tamms-Horsefall proteins​

      • ​Low pH​ & increased electrolyte

Cast Makeup: 

  • Precipitated protein matrix

  • Pure hyaline are devoid of formed elements

Clinical Indication:

  • Nephritis

  • Chronic Renal Disease

  • Diabetic Nephropathy

Hyaline Casts.jpg
Granular Casts

Appearance:​

  • More dense (opaque) 

  • Shorter & broader 

Fine Granular Casts:

  • may appear grey or pale yellow in color

Coarse Granular Casts:

  • may appear as darker

Clinical Indication:

  • Renal Disease

    • Acute Tubular Necrosis (ATN)

    • Advanced glomerulonephritis 

    • Pyelonephritis

    • Malignant nephrosis

  • Chronic lead poisoning​

Mixed Granular Cellular Cast

Causes:

  • Degeneration of cellular casts

  • Direct aggregation of serum proteins into a matrix of Tamm-Horsfall mucoproteins

Mixed cellular granular cast.png
Granular Casts.jpg

Fine Granular Cast

Coarse Granular Cast

Granular Casts.jpg
White Blood Cell Cast

Appearance:

  • Nuclear lobes can be seen

Causes:

Cast Makeup:

  • Aggregates of WBCs that trapped in protein matrix in the renal tubular lumen

Clinical Indication:

  • Inflammation

  • Acute pyelonephritis

  • Occasionally, glomerulonephritis

WBC Cast 1.png
WBC Cast 2.jpg
WBC Cast 3.png
Red Blood Cell Casts

Appearance:

  • Brown to almost colorless

  • Visible RBC cell membranes but without any nucleus

  • RBCs can appear to look concave

Clinical Indication:

Always Clinically Significant

  • Hematuria

  • Usually diagnostic of glomerular diseases

RBC Cast.jpg

Cast Makeup:

  • Aggregates of RBCs that are trapped in protein matrix in the renal tubular lumen

Waxy Casts

Appearance

  • Shorter & broader than hyaline casts

  • Yellowish

  • Broad Waxy Casts are 2-6 times the widths of 

  • Can appear waxy and granular (mixed)

  • Highly refractive

Causes:

  • May originate from: 

    • WBC cast​

    • RBC cast

    • Epithelial Casts

    • Hyaline Casts

Waxy cast 1.jpg

Cast Makeup

  • Composed of homogenous, yellowish materials

Clinical Indication:

  • Chronic Renal Disease

  • Tubular inflammation & degeneration

  • Localized nephron obstruction

  • Malignant hypertension in diabetic diseases

*Note: presence of waxy casts indicates the severity of renal disease

Waxy Cast 2.jpg
Fatty Casts

Appearance

  • Fat bodies are highly refractile on wet mount

  • Fat bodies have maltese cross appearance in polarized light

Cast Makeup:

  • Fat droplets or also called:

    • Fat bodies​

    • oval fat bodies

Clinical Indication

Always Clinically Significant

  • Nephrotic Syndrome

  • Chronic Renal Disease

  • Inflammation & degeneration of renal tubules

  • Lupus

  • Toxic Renal Poisoning

Causes:

  • Fat droplets formed after accumulation & degeneration of fat in the tubular vessels, especially tubular epithelial 

Fatty Cast.png
Fatty Cast 2.png

Maltese Cross seen under polarized light

Sources
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