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