Urine Crystals

Amorphous crystals

The most common crystal in urine

• Non-specific, no bacteria, no organisms

• Seen in both acidic and basic urine

What is amorphous in acidic urine called?

Amorphous urate

• colorless, yellow-brown, aggregates, no specific shape

• If stored in fridge, sediment forms in red brick color

What is amorphous in basic urine called?

Amorphous phosphate

• If stored in fridge, sediment forms in white color or colorless

Why is it important to warm up the urine before testing the urine? (Amorphous crystal)

To dissolve crystals

• Amorphous crystals can interfere with the process of microscopy

• If the urine is stored in fridge, crystals formation will be enhanced.

Calcium oxalate crystal

Shape: Envelope or two pyramids

Characteristics:

• The most common crystals in urine

• Seen in acidic, neutral, or alkaline urine

Others:

• If you see crystals in the fresh urine (30 mins of collection with no refrigeration), patients have a high chance of having calcium-based kidney stones

Why is kidney stone formed?

Metabolism or physiology problem

• Accumulation of crystals → sticks together → kidney stone

Calcium oxalate variation

1. Monohydrate: Associated with ethylene glycol poisoning (drinking anti-freeze)

2. Dihydrate (two pyramid feature)

3. Cylindrical (look at the multiple fields)

Uric acid crystals (urate crystal)

Shape: Pleomorphic; flat, diamond, rhombic, cubic, rossette, different colors

Characteristics:

• Seen in acidic urine

Usually seen in:

• Gout patient

• Chemotherapy: kills the cell → uric acid generated by break down of nucleic acid

Struvite cyrstals (triple phosphate crystal)

Shape: Prisoned, 2-3 sides

Characteristics:

• Composed of magnesium, ammonium, and phosphate

• Seen in alkaline urine

Usually seen in:

• vegan: urine pH goes up due to no absorption of meat

• women with chronic UTI: bacteria multiplies and convert urea to ammonia to increase pH → increase production of struvite stones

Hippuric acid crystals

Shape: Flat, slander, 1 dimensional

Characteristics:

• Seen in acidic, neutral, or slightly alkaline urine

Usually seen in:

• Patient with antibiotics

• Depend on diet and medication

Ammonium urate (biurate) crystals

Shape: spherical, striation associated, spicules (thorn apple), color is dark yellow to brown

Characteristics:

• Seen in alkaline urine

Usually seen in:

• Patients with hepatic problems (liver issues)

• Seen in old urine due to the increased pH

Bilirubin crystal

Shape: very fine needle (usually clustered), yellow to brown color

Usually seen in:

• Several hepatic disorders

Others:

• when urine is stored in a fridge, this crystal form easily

• Presence of bilirubin (liver obstruction)

• Ex) tumor in bile duct → bile cannot empty → bile backflow in the blood → bilirubin seen in the urine → crystalizes in the fridge

Cholesterol

Shape: colorless rectangular plates with a notch in the corners; multilayered and flat

Characteristics:

• Seen in acidic urine

Usually seen in:

• Nephrotic syndrome

• urine stored in the fridge enhances the crystallization process

Cystine crystals

Shape: hexagonal, and crystals overlap and grow together

Characteristics:

• Seen in acidic urine

Usually seen in:

• Associated with an inherited disorder (cystinuria)

• Could differentiate between cystinosis and cystinuria

• PCT defect in amino acid reabsorption

Leucine crystal (rare)

Shape: Concentrated circles form in layers; brown color

Usually seen in:

• Patients with increased leucine production

• Lack of leucine absorption in nephron

• Patients with liver disorders (amino acid metabolism is impaired)

• Patient suspected with aminoaciduria → put the urine specimen in the fridge to enhance the leucine crystal formation

Calcium carbonate crystal (very rare)

Shape: Looks like leucine, with spikes that come out from the center

Characteristics:

• Seen in alkaline urine

Usually seen in:

• patients associated with diet and medications

Tyrosine crystals

Shape: looks like hay stacks

Characteristics:

• Seen in acidic/neutral urine

Usually seen in:

• Patients with tyrosinemia

• Patients with certain liver disorders in which amino acid metabolism is impaired

• usually seen with leucine crystals when patients have tyrosine problem → aminoaciduria

Others

• Don’t get confused with bilirubin crystals

• Bilirubin crystal: brown

• Tyrosine crystal: colorless to yellow

Sulfanomide crystal

Shape: thick crystals, pointy ends (stars)

Usually seen in:

• patients with antibiotics like sulfide drugs

• Associated with drug

• crystals get enhanced when urine is stored in the fridge

Types of kidney stones

1. Calcium oxalate & phosphate (60-70%)

2. Struvite (10-15%)

3. Uric acid (urate) (10-15%)

4. Cystine (rare)