Urinalysis: Urine Crystals

What is the clinical significance of urine crystals? (3)

- most are clinically insignificant
- clinically significant crystals are in freshly voided urine
- presence may imply (not confirm) the presence of urinary calculi

What inherited metabolic disorders can produce amino acid crystals? (2)

- cystine
- leucine

High doses of some drugs can cause the formation of their metabolites. What crystals? (3)

- salicylates
- sulfonamides
- ascorbic acid

How do urine crystals form?

form in vitro as the urine cools to room temperature

How do crystals precipitate out of the solution?

when the concentration in solution is greater than the solubility threshold for that solute

What are the factors that affect crystal formation? (3)

- pH
- solute concentration
- kidney filtration rate

What are the classifications for normal and abnormal crystals? (3)

- normal acidic crystals
- normal alkaline crystals
- abnormal crystals

What are characteristics of urinary crystals? (4)

- pH
- morphology
- polarization and birefringence
- solubility

Crystals commonly found in acidic urine are what? (3)

- uric acid
- urates
- calcium oxalates

Uric acid crystals can have a pH of what?

< 6.0

Uric acid crystals may be ________________ (most common).

amorphous

Uric acid takes on the pigment of urine so it may appear what?

yellow-red brown

What does the concentration of uric acid depend on?

dietary intake of purines and breakdown of nucleic acids

When is uric acid pathologic? What is associated with?

- seen in freshly voided urine
- gout

Uric acid crystals can have ____ sides which can be confused with what?

- 6
- cysteine crystals

T or F: uric acid polarizes light

true

What do sodium urate crystals look like? (2)

- colorless or yellow
- needles or slender prisms

Does sodium urates have clinical significance?

no

Often seen in acidic urine, especially after refrigeration.

amorphous urates

What color can the amorphous urates look like?

pinkish

What pH is calcium oxalate seen with? What condition can you see with calcium oxalate?

- pH usually acidic (or neutral or alkaline)
- present with symptoms of urinary calculi

What can cause excessive oxalate ingestion? (2)

- rhubarb, spinach
- ethylene glycol poisioning

What appearance does calcium oxalate have?

envelope (in the dihydrate form)

What shape can monohydrate calcium oxalate exhibit?

uncommon oval or dumbbell shape that can form rosettes

What are the characteristics of hippuric acid? (5) (pH, clinical significance, color, shape)

- pH usually acidic (can be seen in neutral or alkaline urine)
- rarely seen in urine
- little to no clinical significance
- yellow-brown
- can be seen in needles or clusters

What crystals are found commonly in alkaline urine? (3)

- phosphates
- carbonates
- ammonium biurate

What is the pH where amorphous phosphates appear in? What is the appearance?

- alkaline urine
- sandy appearance

What is the distinct shape of phosphate crystals?

Triple Phosphate (ammonium magnesium)
- also referred to as struvite

What does calcium phosphate crystals look like?

long prisms

What are the characteristics of triple phosphate? (4)

- alkaline urine
- polarizes light
- demonstrates birefringence
- has a coffin-lid appearance or picture frames, feathery, or fern

What is calcium phosphate present in? What can this cause?

- normal urine
- calculi

What are the appearances of calcium phosphate crystals? (3)

- long thin colorless prisms that have one square end and one pointy end
- can be rosettes or star-like
- can have plate-like formations

When is ammonium biurate seen? (4) (pH, what type of specimens)

- alkaline urine
- rarely seen in freshly voided urine
- common in old specimens
- abnormal only if found in freshly voided urine

What is the appearance of ammonium biurate crystals? What is it termed?

- yellow-brown spherical bodies with long, irregular spicules
- termed "thorn apple"

What urine can calcium carbonate crystals be seen in? What is the shape? (3)

- alkaline urine
- rhomboid, spherical, dumbbell

What are abnormal crystals of metabolic origin? (4)

- cystine
- tyrosine
- leucine
- cholesterol

What urine pH is cystine seen in?

acidic urine

What metabolic disorder causes cystine in urine? How?

- cystinuria
- inherited amino transport disorder affecting cystine

What is shape of cystine crystals?

- colorless, retractile hexagonal plate

What can cystine be confused with? How is it differentiated?

- uric acid
- cystine is clear and doesn't polarize light

What urine type is tyrosine seen in? What are some other properties? (2)

- acidic urine
- rarely seen, polarizes light

What disease can tyrosine be seen in?

severe liver disease

What is the shape of tyrosine crystals?

colorless needles in bundles or sheaves

What urine types is leucine seen in? How does leucine polarize light?

- acidic pH
- polarizes light into a maltese cross and the outer edge may resemble "crushed diamonds"

What is the shape of leucine? (2)

- yellow, oily-looking spheres with striations and thick outer boarder
- resembles grapefruit sections

Leucine presence indicates liver disease when seen with what?

tyrosine

What are the characteristics of cholesterol? (4)

- acidic pH
- polarizes light
- free fat from degradation of RTE cells
- may be mistaken for radiologic dyes

What is the characteristic shape of cholesterol?

colorless, large, flat, rectangular plates with one or more corners notched

What type of urine is bilirubin crystals seen in? It also may be present in ___________________.

- acidic urine
- bilirubinuria

What is the shape of bilirubin crystals?

reddish-brown needles or granules

What drugs can cause abnormal crystals of latrogenic? (2)

- aspirin
- sulfa drugs

What supplements can cause abnormal crystals of latrogenic? (3)

- acidic pH
- caffeine
- vitamin C

What are the characteristics of sulfonamide drugs in urine? (3)

- acidic pH
- polarize light
- demonstrate birefringence

What is the shape for sulfonamide drugs?

yellow to brown, needles in sheaves

What can sulfonamide drugs cause as they precipitate out in the nephron?

renal damage

____________________ may look similar to cholesterol crystals.

Radiologic contrast media

Radiologic contrast media will grossly elevate the specific gravity to what?

> 1.050

What is the shape of radiologic contrast media?

needles or elongated rectangles- very dense crystals

Round or oval and retractile. Hexagonal but usually have an indentation. This is an artifact.

starch

What shapes can uric acid be? (5)

- rombus
- stop signs or football
- lemon shapes
- rosettes
- barrel shapes