MICROSCOPIC EXAMINATION OF URINE: CASTS AND CRYSTALS Flashcards
Composed of Tamm-Horsfall (uromodulin) protein excreted by renal tubular epithelial cells
Casts
When other urinary constituents are present they become enmeshed in the cast matrix or attached to the matrix
Casts
Formed in the distal convoluted tubule and collecting ducts (wider casts)
Casts
Reported as the number per low-power field
Casts
Colorless
Hyaline
Orange/red–containing RBCs
RBC
WBCs in cast matrix
WBC
RTE cells attached to cast matrix
Epithelial cell
Bacteria attached to cast matrix
Granular
Coarse or fine granules in the matrix
Granular
Highly refractile, jagged edges and notches
Waxy
Fat droplets and oval fat bodies attached to cast matrix
Fatty
Wider than normal
Broad
Mucus, fibers, increased light
Hyaline
RBC clumps (look for cast matrix)
RBC
WBC clumps (look for cast matrix)
WBC
WBC casts
Epithelial cell
Granular casts
Bacterial
Clumps of small crystals, columnar RTE cells
Granular
Fibers, fecal material
Waxy
Fecal material
Fatty
Fecal material, fibers
Broad
Glomerulonephritis, pyelonephritis, congestive heart failure, stress, exercise
Hyaline
Glomerulonephritis, strenuous exercise
RBC
Pyelonephritis, acute interstitial nephritis
WBC
Renal tubular damage
Epithelial cell
Pyelonephritis
Bacterial
Glomerulonephritis, pyelonephritis, stress, exercise
Granular
Stasis of urine flow, chronic renal failure
Waxy
Nephrotic syndrome, diabetes mellitus, crush injuries
Fatty
Extreme urine stasis, renal failure
Broad
Precipitation of urine solutes affected by
temperature, solute concentration, and pH
are more abundant in refrigerated urine samples
Crystals
Polarized microscopy aids in their identification
Crystals
are found only in acidic or normal urine
Abnormal crystals
Normal Crystals Seen in Acidic Urine
Uric acid crystals
Amorphous urates
Calcium oxalate crystals
Normal Crystals Seen in Alkaline Urine
Triple phosphate crystals
Amorphous phosphate crystals
Calcium carbonate crystals
Ammonium biurate crystals
Abnormal Crystals
Cystine crystals
Cholesterol crystals
Tyrosine crystals
Leucine crystals
Bilirubin crystals
Sulfonamide crystals
Ampicillin crystals
Yellow-brown, flat-sided rhombic plates, wedges, and rosettes
Uric acid crystals
Sources of error
○ Cystine crystals (uric acid crystals polarize and cystine crystals do not polarize)
Uric acid crystals
Clinical significance
○ Patients receiving chemotherapy
○ Lesch-Nyhan disease
Uric acid crystals
Small spheres producing brick-dust (uroerythrin) or yellow-brown sediment
Amorphous urates
May also be seen in alkaline urine
Calcium oxalate crystals
The dihydrate form is envelope shaped; clumps in fresh urine may indicate renal calculi
Calcium oxalate crystals
The monohydrate form is oval or dumbbell shaped; presence of this form indicates ethylene glycol (antifreeze) ingestion
Calcium oxalate crystals
Coffin-lid shaped
Triple phosphate crystals
Associated with a very high pH and bacteria found in old specimens
Triple phosphate crystals
Produce a white precipitate after refrigeration
Amorphous phosphate crystals
Dumbbell and spherical shapes
Calcium carbonate crystals
Produce gas with acetic acid
Calcium carbonate crystals
Yellow-brown thorny apple-shaped crystals
Ammonium biurate crystals
Associated with old specimens with bacteria
Ammonium biurate crystals
Hexagonal flat plates
Cystine crystals
Clinical significance
○ Aninherited disorder that inhibits the reabsorption of cystine by the renal tubules (cystinuria); renal calculi form at an early age
Cystine crystals
Rectangular plates with notched corners, highly birefringent under polarized light
Seen in refrigerated urine and accompanied by fatty casts and oval fat bodies
Cholesterol crystals
Clinical significance
○ Nephrotic syndrome
Cholesterol crystals
Yellow needle-shaped forms in clusters or rosettes
Tyrosine crystals
Clinical significance
○ Severe liver disease
Tyrosine crystals
Yellow-brown spheres with concentric circles
Leucine crystals
Seen in conjunction with tyrosine crystals
Leucine crystals
Clinical significance
○ Severe liver disease
Leucine crystals
Bright yellow clumped needles and granules
Bilirubin crystals
Clinical significance
○ Liver damage often from viral infections that damage the renal tubules, preventing reabsorption of bilirubin
Bilirubin crystals
Needle, rosette, and rhombic shapes
Sulfonamide crystals
Clinical significance
○ Inadequately hydrated patients taking sulfonamide medications
Sulfonamide crystals
Colorless needles that form clumps after refrigeration
Ampicillin crystals
Clinical significance
○ Inadequately hydrated patients
Ampicillin crystals