Urine Sediment

(Am J Kidney Dis 2008;51:1052)

Method

  • Centrifuge fresh sample (prox. port if Foley) × 3-5 min at ↣ 1500-3000 rpm
  • pour off supernatant in one motion
  • resuspend pellet by agitating base of tube
  • pour suspension onto slide w/ coverslip
  • view under “high dry” power
  • phase contrast for RBC morphology

Urine Sediment Cells

  • RBCs: assess amount & morphology (many dysmorphic → glomerular)
  • WBCs: PMNs (UTI) vs. eosinophils (AIN; may require special stain)
  • Epithelial cells: tubular (ATN), transitional (bladder or ureters), squamous

Urine Sediment Casts

  • Proteins molded in lumen of renal tubule ± entrapped cellular elements RBC → GN
  • WBC → AIN, pyelonephritis, GN
  • Granular (“muddy brown”): degenerating cellular casts → ATN
  • Tubular cell → ATN
  • Hyaline: Tamm-Horsfall protein (nonspecific)
  • Waxy and broad → advanced chronic kidney disease

Urine Sediment Crystals

  • Calcium oxalate monohydrate: spindle, oval, or dumbbell shaped
  • Calcium oxalate dihydrate: envelope shaped or octahedral
  • Uric acid: variable shape; polychromatic under polarized light
  • Cystine: hexagon shaped
  • Struvite: coffin-lid shaped; seen in chronic UTI with urea-splitting organisms
  • Drugs: sulfa, protease inhibitors: “shocks of wheat”; acyclovir: fine needles