Calcium Oxalate crystals usually take on the dihydrate form, appearing like two pyramids joined at the base. They may be described as “envelope-shaped.”

Monohydrate crystals are less common and have a wider variety of shapes, such as oval, elliptical, or dumbbell-shaped. These forms may be confused for RBCs under normal light but can be differentiated by their birefringence under polarized light.

Found in acidic or neutral urine. Soluble in dilute hydrochloric acid.

Calcium Oxalate crystals may appear normally in urine after ingestion of food rich in oxalic acid or after a large intake of vitamin C. They may also indicate renal calculi.

Triple phosphate crystals are typically rectangular prisms with a “coffin lid” appearance. Rarely, partially dissolved triple phosphate crystals may have a fern or feather-like appearance.

lly rectangular prisms with a “coffin lid” appearance. Rarely, partially dissolved triple phosphate crystals may have a fern or feather-like appearance.

Found in alkaline or neutral urine. Soluble in dilute acetic acid.

Usually not clinically significant but may indicate struvite calculi.

Uric acid crystals are typically diamond or lemon-shaped. Clumps of them may form a rosette. Less commonly, they may appear as barrels, star-like clusters, or other hexagonal shapes.

Found in acidic urine. Soluble in sodium hydroxide.

Can appear in normal urine but may also be seen in conditions such as gouty nephropathy, hyperuricemia, or uric acid stones.

Leucine crystals typically appear as yellow-brown spheres with concentric rings. Under polarized light, these crystals show a pseudo “Maltese Cross.” Commonly found alongside tyrosine crystals.

Found in acidic urine. Soluble in hot acetic acid, hot alcohol, and sodium hydroxide. Insoluble in sodium chloride.

Leucine crystals can be found in urine of patients with severe liver disease or maple syrup urine disease.

Cystine crystals a clear, colorless hexagons that may stack. Birefringence under polarized light is weak or absent but may be more apparent when crystals are stacked.

Found in acidic urine. Soluble in hydrochloric acid and alkali. Insoluble in boiling water, acetic acid, and alcohol.

Found in urine of patients with congenital cystinuria.

Bilirubin crystals usually appear as small clusters of yellow-brown or reddish-brown needles. Bilirubin in urine typically stains ther elements in the urine as well.

Found in acidic urine. Soluble in acetic acid, hydrochloric acid, and sodium hydroxide. Insoluble in alcohol.

The presence of the crystals themselves is not significant. Rather, the presence of bilirubin in the urine in general is indicative of liver disease.

Amorphous Urates appear as granular material in the sediment. Brownian motion of these granules may make them appear as bacteria, so care must be taken with identification. Warming the specimen usually dissolves these crystals, allowing for proper identification of elements the sediment that may otherwise be obscured. Macroscopically, it has a “brick dust” appearance.

Found in acidic urine. Soluble in alkali and heat. Insoluble in acetic acid.

Not clinically significant.

Check out this post on a urine with amorphous urates.

• Ammonium Biurate
• Amorphous Phosphates
• Hippuric Acid
• Struvite
• Tyrosine
• Xanthine