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How are crystals in the urine formed?
- Formed by the precipitation of urine salts, organic compounds, and meds
- Can be altered by temperature, pH, and urine concentration
- If an increased amount of a solute is present when the glomerular ultrafiltrate passes through the renal tubules, the ultrafiltrate becomes saturated - leading to the solute precipitating into a characteristic crystal form
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What is the most important factor when identifying crystals in urines?
pH
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In what pH are all clinically significant crystals found?
Acidic and neutral urine
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What acidic crystals are:
Formed from the urate salts of Na, K, Mg, and Ca
No clinical significance
Small yellow-to-brown granules usually in large amounts
May also be produced when refrigerated due to the presence of uroerythrin
Amorphous urates
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How do you get ride of amorphous urates when you need to see the sediment behind them?
- Dissolve at an alkaline pH
- Heating above 60 degrees celcius
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What acidic crystals are:
Seen in gout, chemotherapy for leukemia, and Lesch-Nyhan syndrome
Appear yellow-to-orange/brown but can be colorless
Pleomorphic (many) shapes that include four sided flat plates, rhombic plates, wedges, and rosettes
Uric acid
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What acidic crystals are:
Formed from oxalic acid (found in tomatoes, asparagus, spinach, berries, and oranges and Vit C)
Colorless, dihydrate form appears as octahedral envelope or 2 pyramids joined at their bases
Monohydrate form appears as dumbbell or oval shaped
Associated with renal calculi formation and seen in poison centers where children have ingested ethylene glycol (antifreeze)
Calcium oxalate
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What acidic crystals are:
Formed when urine bilirubin exceed its solubility
Appear as fine needles or granules that are yellow-brown in color
Associated with liver disease
Casts may contain these crystals in cases of viral hepaptitis when there is reanl tubular damage
Bilirubin crystal
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What acidic crystals are:
Fine delicate needles, colorless-yellow found in clumps or rosettes
Associated with severe liver disease and inherited diseases that affect amino acid metabolism
May be seen with leucine in urines that test positive for bilirubin
Tyrosine
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What acidic crystals are:
Yellow-brown, oily looking spheres with concentric circles and radial striations
May be found with tyrosine crystals
Associated with severe liver disease and inherited diseases that affect amino acid metabolism
Leucine
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What acidic crystals:
Colorless hexagonal plates
Associated with congenital disorder that inhibits renal tubular reabsorption of of cystine and renal calculi formation
Cystine
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What acidic crystals:
Clear, flat, rectangular plates with a notch in one or more corners
Seen with fatty casts and oval fat bodies
Associated with nephrotic syndrome and other disorders that produce lipiduria
Cholesterol
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Name the crystals that form due to meds
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What alkaline crystal:
Small, colorless granules
Refrigerated samples appear as white sediment
Not clinically significant
Amorphous Phosphate
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What alkaline crystal:
Colorless, 3-6 sided prism often resembling a coffin lid
May be associated with UTIs but not clinically significant
Triple phosphate
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What alkaline urine:
Colorless, thin prisms or rectangular plates
May be associated with renal calculi formation but not clinically significant
Calcium phosphate
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What alkaline urine:
Seen in old urine samples
Converts to uric acid crystals if acetic acid is added
Yellow-brown spheres with striations on the surface, also can show irregular, thorny projections (thorny apples)
Ammonium biurate
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What alkaline urine:
Appears as small, colorless crystals having dumbbell or spherical shapes
Not clinically significant
Calcium carbonate
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