URINARY CRYSTALS

CM LEC 5

URINARY CRYSTALS

●Formed by the precipitation of urine solutes such as inorganic salts, organic compounds, and medications. ●Precipitation is subject to changes in temperature, solute concentration, and pH. ●Solutes precipitate more readily at low temperatures. ●Specimens that have remained at room temperature or refrigerated, expect that there will be crystal formation in the specimen. ●The pH of a specimen becomes a valuable aid in the identification of crystals because this can also determine the type of chemicals precipitated. ●Organic and iatrogenic compounds crystallize more easily in acidic pH. ●Inorganic salts are less soluble in neutral and alkaline solutions. ● Calcium oxalate precipitates in both acidic and neutral urine.

• amorphous urates crystals

• uric acid crystals

• sodium urates crystals

• calcium oxalate crystals

NORMAL CRYSTALS SEEN IN ACIDIC URINE

AMORPHOUS URATES

●Yellow-brown granules, may appear in clumps. ●Encountered frequently in refrigerated specimens but this will disappear when the urine is warmed. ●PINK SEDIMENT caused by accumulation of the pigment uroerythrin on the surface of the granules. ●pH >5.5 ●random sand-like appearance of the granules

URIC ACID CRYSTALS

●Seen in a variety of shapes- rhombic, four-sided flat plates (whetstones), wedges, rosettes. ●Some also have that six-sided shape, similar to cysteine crystals. ●Yellow-brown in color, but they may also be colorless. ● Highly birefringent under polarized light. ●Increased amounts of uric acid crystals when there are increased levels of purines and nucleic acids, seen in patients with leukemia who are receiving chemotherapy, Lesch–Nyhan syndrome, and gout.

SODIUM URATES CRYSTALS

●These are needle-shaped and seen in synovial fluid (fluid in between joints) during episodes of gout. ●Also appears in urine. ●Examples of joints? Your knee, that's a joint.

CALCIUM OXALATE CRYSTALS

●Acidic/neutral urine ●2 forms 1. Dihydrate - most common form. Colorless, octahedral envelope or as 2 pyramids joined at their base. 2. Monohydrate - less frequently seen, oval or dumbbell shaped. ●Both forms are birefringent under polarized light, and you have to distinguish monohydrate form from nonpolarizing RBCs. ●Finding clumps of calcium oxalate crystals in fresh urine may be related to the formation of renal calculi (kidney stones). ● Renal calculi is composed of calcium oxalate. ●Food high in oxalic acid, such as tomatoes and asparagus, and also ascorbic acid, since oxalic acid is an end product of ascorbic acid metabolism. ●Pathologic significance: presence of monohydrate forms in cases of ethylene glycol (antifreeze) poisoning.

• amorphous phosphate crystals

• triple phosphate crystals

• calcium phosphate crystals

• calcium carbonate crystals

• ammonium biurate crystals

NORMAL CRYSTALS SEEN IN ALKALINE URINE:

AMORPHOUS PHOSPHATE CRYSTALS

●Granular in appearance, similar to amorphous urates. ●Seen in alkaline urine (alkaline pH) ●Present in large quantities after refrigeration ●If there's pink sediment: WHITE precipitate (does not dissolve upon warming).

TRIPLE PHOSPHATE CRYSTALS

● Ammonium Magnesium Phosphate Crystal ●Prism shape that resembles “coffin lids” ●Birefringent ● No clinical significance ●Often seen in highly alkaline urine associated with the presence of urea splitting bacteria.

CALCIUM PHOSPHATE CRYSTALS

● Not encountered frequently ● Colorless, flat rectangular plates or thin prisms often in rosette formations. ● Rosette forms may be confused with sulfonamide crystals when the urine pH is in neutral range. ●To double check: dissolve in dilute acetic acid (which sulfonamides do not dissolve in as compared to calcium phosphate). ● Calcium phosphate - common constituent of renal calculi.

CALCIUM CARBONATE CRYSTALS

●Small and colorless, with dumbbell or spherical shapes ● May occur in clumps that resemble amorphous material ●To distinguish calcium carbonate from amorphous: formation of gas after the addition of acetic acid ●Birefringent ● No clinical significance

AMMONIUM BIURATE CRYSTALS

●“thorny apples” appearance, spicule-covered spheres ● Resemble other urates → dissolve at 60°C and convert to uric acid crystals when glacial acetic acid is added. ● Mostly encountered in old specimens and may be associated with the presence of urea splitting bacteria.

• cystine crystals

• cholesterol crystals

• radiographic dye crystals

• sulfonamide crystals

• ampicillin crystals

ABNORMAL URINE CRYSTALS:

CYSTINE CRYSTALS

●found in the urine of people with metabolic disorder that prevents the reabsorption of cystine by the renal tubules ● Cystinuria ●Patients who have cystinuria tend to form renal calculi at an early age ●Appear as colorless, hexagonal plates, may be thick or thin ● Disintegrating forms may be seen in the presence of ammonia ●It is difficult to differentiate from colorless uric acid crystals ●To differentiate cystine crystals from uric acid crystals: uric acid crystals (birefringent and thick); cystine crystals (polarizing capability) ●Positive confirmation for cystine crystals: Cyanide Nitroprusside Test

CHOLESTEROL CRYSTALS

● Rarely seen unless specimens have been refrigerated because lipids remain in droplet form. ● Resembles rectangular plate with a notch in one or more corners. ●Associated with disorders producing lipiduria (nephrotic syndrome). ●Seen in conjunction with fatty casts and oval fat bodies. ● Highly birefringent with polarized light

RADIOGRAPHIC DYE CRYSTALS

●Appear similarly to cholesterol crystals, also highly birefringent ● Comparison is made of other urinalysis results as well as patient history in order to confirm what type of crystal is. ●If a patient has a history of taking radiographic dye, possibly the crystals seen in urine sediment is radiographic dye. ●Specific gravity of urine specimen is markedly elevated when measured by refractometer

SULFONAMIDE CRYSTALS

●Found in urine of patients being treated for UTI ●Inadequate hydration of patients → primary cause of sulfonamide crystallization ●Appearance in fresh urine suggest tubular damage ●Variety of shapes - needles, rhombics, whetstones, sheaves of wheat, and rosettes.

AMPICILLIN CRYSTALS

●Precipitation of antibiotics is not frequently encountered except after massive doses of this penicillin compound without adequate hydration. ● Colorless needles that tend to form bundles after refrigeration

• tyrosine crystals

• leucine crystals

• bilirubin crystals

CRYSTALS ASSOCIATED WITH LIVER DISEASE:

TYROSINE CRYSTALS

●Fine colorless to yellow needles that frequently form rosettes or clumps. ● Usually seen in conjunction with leucine crystals ●Specimen is positive for bilirubin ● May be encountered in inherited disorders of amino acid metabolism ●If the specimen is positive for bilirubin, expect dark yellow color. When you do a shake test, there's formation of a stable yellow foam.

LEUCINE CRYSTALS

●Yellow-brown spheres concentric circles and radial striations. ●Seen less frequently than tyrosine crystals

BILIRUBUN CRYSTALS

●Present in patients with haptic disorders ●Appear as clumped needles or granules with the characteristic yellow color of bilirubin ●Positive chemical test result for bilirubin ●Viral hepatitis - bilirubin crystals may be found incorporated into the matrix of casts.