Crystals, Organisms, and Artifacts

Crystals:
Most urine crystals are normal and offer no clinical significance. Normal crystals can be found in both acidic or alkaline pH; whereas, all abnormal crystals are found only in acidic pH. Below is a list of normal and abnormal crystal types with characteristics of each.

Normal crystals:

Uric acid crystals:

acid pH
soluble in alkali and heat
insoluble in HCl and acetic acid
multiple forms
highly birefringent (can be seen in polarized microscopy)

Hippuric acid crystals:

colorless, 6-sided prisms, needles, or rhombic plates
uncommon
confused with triple phosphate crystals

Calcium oxalate crystals:

acid pH but may be seen in neutral or slightly alkaline pH
soluble in HCl and 90% ethyl alcohol
insoluble in acetic acid
can cause kidney stones
octahedral envelope shape or ovoid dumbbell shape

Triple phosphate crystals:

alkaline pH
effervesces with HCl or acetic acid
insoluble in alkali
granule or dumbbell shape

Calcium phosphate crystals:

alkaline pH
soluble in dilute acetic acid
insoluble in alkali
large flat-shaped or wedge-shaped prisms
appear singly or in rosettes

Ammonium biurate crystals:

alkaline pH
soluble in acetic acid
insoluble in ammonium hydroxide
yellowish-brown color with “thorn apple” shape
indicator of incorrect specimen preservation

Abnormal crystals:

Leucine:

acid pH
soluble in sodium hydroxide and hot water
insoluble in HCl
spheroid with concentric striations
seen in liver disorders
often seen with tyrosine crystals

Tyrosine crystals:

acid pH
soluble in HCl and sodium hydroxide
insoluble in alcohol and acetic acid
colorless to yellow-brown single needles or rosettes
seen in liver disorders or tyrosinemia (genetic)
often seen with Leucine crystals

Cystine crystals:

acid pH
soluble in HCl, sodium hydroxide, ammonium hydroxide
insoluble in acetic acid
thin, colorless, hexagonal plates
may appear wrinkled while dissolving
can be confused with uric acid
can be differentiated using polarization; cystine crystals are not bi-refringent
found in cystinuria (inherited)

Bilirubin crystals:

acid pH
soluble in acetic acid, HCl, sodium hydroxide, and acetone
insoluble in alcohol
typically yellow-brown needles or granules
found in hepatic disorders

Cholesterol crystals:

acid pH
soluble in chloroform or ether
insoluble in dilute acids and alkalis
associated with nephrotic syndrome
found with ↑urinary protein, ↑serum cholesterol, and ↓serum albumin

Sulfonamide crystals:

acid pH
soluble in acetone and alkali
insoluble in acetic acid
wide variety of shapes
seen in urine during drug therapy
confirm with biochemical test before reporting

Radiopaque dye crystals:

associated with a very high specific gravity, > 1.035
variable shape but usually flat needles or sheaves with round globules
highly bi-refringent (seen in polarized light)
commonly mistaken for tyrosine or sulfonamide crystals

Organisms and artifacts:
Anyone who tries to make the argument urine is sterile hasn’t been through a urinalysis rotation!

Yeast:

Seen in urinary tract infections (UTIs) of diabetics
Non-budding yeast can be confused with RBCs
RBCs can be lysed using dilute HCl to distinguish

Trichomonas vaginalis:

This parasite is commonly seen in urine
More frequently seen in females but can be seen in males
Can be confused with WBCs
Flagella motility is necessary for identification

Sperm:

Seen in urine of females and males
Not clinically significant

Bacteria:

Bacteria in a clean catch urine sample is indicative of a UTI if there are bacteria and WBCs.
Clean catch urine is basically midstream urine. It’s used to avoid         contamination with skin bacteria etc.
Common bacteria will cause a positive nitrate biochemical test
Numerous bacteria without WBCs can indicate poor specimen handling
Bacteria and WBCs can be more visible in phase microscopy

Fibers:

May be present as contaminants from clothing or fecal material
Can be confused with hyaline or waxy casts
Fibers will be seen in polarized light, casts will not be seen

Starch:

Contaminant from powdered lab gloves
Greenish appearance and t-shaped notch in the center
Produces a pseudo “maltese cross” when polarized
Can be confused with fat droplets