Cast

• Casts

  Only element found in urine that are unique to the kidneys
• Cast formation

  1. Formed primarily within the lumen of DCT and Collecting Ducts

  2. Favored by urine stasis, acid urine, and sodium and calcium presence
• UROMODULIN/TAMM-HORSFALL


  Matrix of cast formation produced by the RTE
• Cylindroids


  • Casts with tapered end produced at the junction of ALH and DCT
  • Incomplete cast formation or disintegration
  • Same significance as casts
• Cylindruria

  Presence of cast in the urine
• Site of cast formation is DCT, ALH, & CD
• Order of cast degeneration

  Hyaline casts (mucus) -> cellular casts (RBC, WBC, RTE) -> Granular Cast (Coarse and Final) -> Waxy cast (Final degeneration product)
• Urine examination for cast detection

  1. Scanning is performed using the LPO along the edges of the coverslip

  2. Observed under subdued light because cast matrix has low refractive index

  3. Casts are dissolved quickly in dilute alkaline urine

  4. Casts must be identified as to composition using the HPO

  5. Reported as average #/LPO
• Hyaline cast

  • Only normal and most frequently seen cast
  • Colorless, homogenous, and has some RI with urine; consist almost entirely of Tamm Horsfall protein
  • Nonpathologic: strenuous exercise, dehydration, heat exposure, emotional stress
  • Pathologic: acute glomerulonephritis, pyelonephritis, chronic renal disease, congestive heart failure
  • Normal value: 0-2 /LPF
• Red blood cell cast

  • Orange-red color, cast matrix containing RBCs
  • Glomerulonephritis, strenuous exercise
• White blood cell cast

  • Cast matrix containing WBCs
  • Pyelonephritis, Acute interstitial nephritis
  • Presence indicates the need to perform bacterial cultures
• Epithelial cell cast


  • RTE cells attached to protein matrix
  • Renal tubular damage
• Granular cast


  • Coarse and fine granules in a cast matrix
  • Glomerulonephritis, Pyelonephritis, stress and exercise
  • Represents the disintegration of cellular cast
  • Granular dirty brown cast - hemoglobin degradation products (bc of methemoglobin); acute tubular necrosis, massive hemoglobinuria
• Waxy cast

  • Highly refractile cast with jagged edges and notches
  • Stasis of urine flow, chronic renal failure
• Fatty cast


  • Brittle; ground glass appearance with cracks and fissures
  • Pink - KOVA STAIN
  • Fat droplets and oval fat bodies attached to a protein matrix
  • Nephrotic syndrome, toxic tubular necrosis, diabetes mellitus, crush injuries
• Broad cast

  • Wider than normal cast matrix
  • Indicates distention of tubular lumen
  • Granular and waxy casts are the most common broad casts
  • Bile-stained broad, waxy casts are seen in tubular necrosis in viral hepatitis
  • Extreme urine stasis and renal failure
  • Also called Renal Failure Cast