CH2514 3.5 Microscopic Examination, Crystals/Casts

Flashcards about Crystals and Casts found in Urine

Abnormal Crystals

Will ALWAYS be found in acidic urine.

Uric Acid Crystals

Yellow-brown cystals with a rhombic, four sided shape. Associated with gout, leukemia patients receiving chemotherapy, and increased purine/nucleic acid levels.

Amorphous Urates

Granular sediment, yellow-brown or pink color. Found in acidic urine with pH greater than 5.5; common in refrigerated specimens and may dissolve if warmed.

Calcium Oxalate Crystals

Birefringent under polarized light. Dihydrate Calcium Oxalate (Envelope-shaped) or Monohydrate Calcium Oxalate (Oval or Dumbbell shaped).

Monohydrate Calcium Oxalate

Associated with ethylene glycol poisoning.

Amorphous Phosphates

Granular sediment found in alkaline urine, white-colorless. Present in large quantities after refrigeration, do NOT dissolve when warmed.

Calcium Phosphate

Can be confused with sulfonamide crystals, acetic acid can be used to differentiate (will dissolve, sulfonamide will not). Not clinically significant.

Triple Phosphate (Ammonium Magnesium Phosphate)

“Coffin lid” prism, or fern leaf shaped. Found in highly alkaline urine and patients with UTIs.

Ammonium Biurate

“Thorny apples”, yellow brown in color. Occurs in old specimens, dissolves at 60 degrees celcius.

Calcium Carbonate

Small dumbbell or spherical shape, may be confused with bacteria or amorphous materials. No clinical significance.

Cystine

Hexagonal plates that are difficult to differentiate from uric acid crystals. Found in cystinuria.

Cholesterol

Colorless rectangular plates with notched corners. Highly birefringent and associated with nephrotic syndrome.

Leucine

Spheres with concentric circles and radial striations, yellow-brown in color. Accompanied by tyrosine crystals.

Tyrosine

Fine needles in clumps or rosette, colorless to yellow. Seen with leucine crystals, chemical bilirubin test will be positive.

Bilirubin

Clumped needles or granules, yellow in color. Seen in disorders that produce renal tubular damage.

Sulfonamides

Variety of shapes including needles, rhombics, whetstones, sheaves of wheat, rosettes. Color varies from colorless to yellow brown. Inadequate patient hydration is the primary cause, and in a fresh urine may suggest tubular damage.

Radiographic Dye

Flat plates (similar to cholesterol crystals); colorless and highly birefringent. Will have a very high specific gravity when measured with a refractometer.

Ampicillin

Found in patients following large doses of ampicillin who are not adequately hydrated. Needles which form bundles after refrigeration.

Uromodulin (Tamm-Horsfall protein)

The major constituent of urinary casts.

Cylindruria

An increase in urinary casts.

Hyaline Casts

Most frequently seen, and made up entirely of uromodulin. Easy to overlook if not using low light, refractive index is similar to that of urine. 0-2 per LPF is normal.

RBC Casts

Orange-red color; cast matrix contain RBCs. Confirmed by free RBCs in the urine, and a positive reagent test strip for blood. Indicates bleeding within the nephron, primarily glomerulonephritis.

WBC Casts

Composed of neutrophils and may appear granular, indicate inflammation/infection in the upper urinary tract (pyelonephritis) accompanied by RTE casts, not seen in lower UTI. Matrix must be present to confirm a cast.

Renal Tubular Epithelial (RTE) Casts

Represent advanced tubular destruction; associated with heavy metal, chemical or drug-induced toxicity, viral infections, or allograft rejection. May accompany WBC casts in pyleonephritis.

Granular Casts

Occur as a result of disintegrating cellular casts; start off as coarse granules but will appear as fine granules if there is prolonged urinary stasis. Associated with glomerulonephritis, pyleonephritis, and stress/exercise.

Waxy Casts

Brittle and highly refractive, appear fragmented with jagged ends and notches; occur when hyaline and granular casts degenerate due to extreme urine stasis. Seen in chronic renal failure and extreme urine stasis.

Broad Casts

Wide casts, presence indicates destruction and widening of the tubular walls, represent extreme urine stasis. Can be any type of cast, but waxy and granular are most common. AKA renal failure casts.

Fatty Casts

Will have fat droplets and oval fat bodies attached to the protein matrix; primarily found in Nephrotic Syndrome. Highly refractive under bright field microscopy.

Oval Fat Bodies

Lipid-containing RTE cells; RTE cells absorb lipids in the glomerular filtrate (cholesterol, triglycerides or neutral fat).

Perform Microscopy

Done if a test strip is positive for blood, leukocyte esterase, protein, and/or nitrite.

Cyanide-nitroprusside test

Confirms precense of cystine crystals, vs. uric acid crystals.

Dirty brown RBC cast

Hemoglobin cast, associated with acute tubular necrosis. Will be seen with RTE cells and a positive reagent strip test for blood.