Urinalysis Crystals
What are urine crystals?
Crystalluria- an oversaturation of crystal sediment in urine specimen
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Many factors can contribute to their formation so some types are less clinically significant than others. It is important to identify & distinguish these crystals with a fresh, unrefrigerated urine specimen.
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*Note: Even if its considered significant or not, if there are massive amount of any type of crystal it can mean something clinically significant. So it is important to take note of it.
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For example, even though ​uric acid crystals are common in urine it can be an indicator of gout if seen in large amounts.
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Below is list of clinically significant & clinically insignificant (common) crystals:
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Acid Crystals
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Alkaline Crystals
Clinically Insignificant
(Common Crystals)
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Uric acid
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Calcium Oxalate
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Amorphous Urates
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Triple Phosphate
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Ammonium Biurate
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Amorphous Phosphate
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Calcium Carbonate
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Calcium Phosphate
Clinically Significant
(Abnormal Crystals)
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Amino Acid Crystals:
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Leucine​
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Tyrosine
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Cystine
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Cholesterol​
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Bilirubin
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Ampicillin
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Sulfonamides

Acidic Urine Crystals
Amorphous Urates

Description:
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Very small & yellow- brown granules in clusters
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Similar to sand​
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"Brick Dust"- pink-orangish color​
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caused by Uroerythrin deposits on urate crytals​
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Crystal Makeup:
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Sodium (Na+)
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Potassium (K+)
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Magnesium (Mg+)
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Calcium (Ca+)
Clinical Indication:
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Precipitation is enhanced by refrigeration
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Indicates Old sample​
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Dissolves in when heated or in alkaline urine
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Precipitates in acetic acid
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Uric Acid

Description:
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Usually yellow to orange-brown
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Birefringent under polarizing light
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Diamond shape:
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​may cluster as a "rosette"
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Crystal Makeup:
Catabolism products of:​
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Purine Nucleic Acid
Clinical Indication:
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Gout (in large amounts)- inflammation in big toe
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Cytotoxic drugs
Calcium Oxalate

Description:
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Colorless
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Dihydrate form:
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"Envelope" (Octahedral)
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Monohydrate form:​
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"Dumbbell" or small ovoid​
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Birefringent under polarizing light​
Clinical Indication:
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Often seen in normal urine
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High Ascorbic Acid
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Ingestion of:
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Tomatoes​
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Asparagus
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Spinach
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Oranges
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Eth​ylene Glycol Poisoning

Bilirubin

Description:
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Fine needles
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Can also be seen as granules or plates
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Always yellow-brown
Clinical Indication:
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Always considered abnormal
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if very high concentrations of bilirubin in the urine
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Liver disease
Confirmatory Test: Bilirubin Strip
Amino Acid Crystal: Tyrosine
Description:
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Fine, delicate needles frequently seen in clusters of sheaves:
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"Stacks of Wheat"​
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Colorless or yellow​

Clinical Indication:
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Sometimes seen in severe liver disease
Seen more often than Leucine crystals because it is less soluble in acidic urine
Amino Acid Crystal:
Leucine
Description:
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Yellow-brown Spheres with concentric/radial striations
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Highly refractile
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Can be seen in urine containing tyrosine crystals if alcohol is used to precipitate

Clinical Indication:
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Sometimes seen in severe liver disease
Can be mistaken for fat globules (or vice versa)
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Unlike fat globules, leucine will not stain with fat stains or appear as maltese cross under polarization
Bactrim (sulfonamide) has a similar appearance, so it is important to check patient history
Amino Acid Crystal: Cysteine
Description:
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Colorless, flat, hexagonal plates
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Sides may be uneven​
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Refractile
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Crystals appear layered​ as it tends to clump​​

Clinical Indication:
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Congenital cytinosis
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Cystinuria & Homocystinuria
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Deposits in tubules as caliculi/ kidney stones causing damage​
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Can be confused with uric acid crystals
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Use Sodium Cyanide Confirmatory Test to distinguish
Ampicillin

Description:
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Appear as long, thin, colorless needles or prisms
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May aggregate in small clusters
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If refrigerated, may form large clusters
Indication:
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Rarely seen
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Large ampicillin dosage​
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Cholesterol

Description:
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Clear, flat, rectangular plates with "notched corners"
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Soluble in chloroform & ether
Clinical Indication:
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Rarely seen
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Always seen with positive protein & fat droplets, fatty casts or oval fat bodies
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Seen in Nephrotic Syndrome & other renal damage
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Conditions that produce chyluria​
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Sulfonamide
Description:
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Highly refractife & birefringent
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Yellow-brown sheaves or clusters of needles


Clinical Indication:
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Seen in patients undergoing antimicrobial therapy with sulfa-drugs
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Sulfa-drugs have now been modified to be more soluble, so sulfonamide crystals are actually rarely seen​
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Sulfadiazine
Description:
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Yellow to brown bundles of wheat
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Constriction may be central or excentric​
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Sulfamethoxazole
Description:
Bactrin & Septim more commonly seen
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Brown rosettes or spheres with irregular striations
Alkaline Urine Crystals
Amorphous Phosphates

Description:
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Fine, colorless masses resembling sand
Clinical Indication:
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Normal in urine- Clinically Insignificant
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tends to obscure other more significant sediment​
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Presence is enhanced by refrigeration
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Microscopically indistinguishable from amorphous urates:
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Distinguishable by urine pH & solubility
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Amorphous phosphate will precipitate white rather than the pink- orange of amorphous urates
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Soluble in acid & will not dissolve when heated to 60°C
Triple Phosphate

Description:
Colorless and will comes in different forms & sizes:
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Coffin Lids- most common form
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may also be seen as fern leaf or feather​​
Indication:
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Can be seen in normal healthy individuals
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Associated with UTI
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Present in formation of caliculi
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Also called Struvite
Calcium Phosphates

Description:
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Colorless thin prisms in rosettes or star-shaped
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"Stellar Phosphates"​
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Tend to have 1 tapered or pointed end & the other end is squared off​
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Ammonium Biurate



Description:
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Yellow-brown spheres with striations
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Can have irregular spicules & spines
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"Thorny Apple"​
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Clinical Indication:
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Usually seen in old specimens
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Not clinically significant unless seen in fresh urine
Calcium Carbonate

Description:
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Very small granular crystals
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Can be misidentified as bacteria
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Usually found in pairs
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"Dumbbell Shape"​ or spheres
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Sources:
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Aryal, S. (2020, January 04). Types of Crystals in Urine: Infection. Retrieved May 07, 2020, from https://microbenotes.com/types-of-crystals-in-urine/
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Barsanti, J. (2011, December 15). Urinary Disorders. Retrieved June 05, 2020, from https://www.sciencedirect.com/science/article/pii/B9781437706574000077
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Bishop, M. L., Fody, E. P., & Schoeff, L. E. (2010). Clinical chemistry: Techniques, principles, correlations (7th ed.). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
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D. (2014). Variations of Uric acid crystals in urine. Retrieved May 07, 2020, from http://www.medical-labs.net/variations-of-uric-acid-crystals-in-urine-2351/
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LAB CE. (2001). Crystals of Clinical Significance. Retrieved June 06, 2020, from https://www.labce.com/spg2087057_crystals_of_clinical_significance.aspx
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Lab CE. (2016). Review of Common Crystals. Retrieved June 04, 2020, from https://www.labce.com/spg30204_review_of_common_crystals.aspx
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Salazar, E. (2018). Microscopic Examination Crystals [PowerPoint slides]. Retrieved from UTMB Blackboard