The presence of crystals is called
crytalluria. The type of crystal that
forms, depends on the pH of the
urine. Other factors include urine
concentration, temperature, and the
solubility of the elements.
Refrigeration of samples can either
increase or decrease the number of
crystals in the sample. The materials
that make up crystals are less soluble
at lower temperatures. Sometimes
crystals dissolve when a refrigerated
sample is warmed to room
temperature.
Struvite crystals are also referred to
as triple phosphate crystals. They are
found in alkaline to slightly acidic
urine. Struvite crystals are prisms
with tapering sides and are described
as resembling a coffin. These are the
most common type of crystal that
you will identify.
How a stone is formed: Urea is a
component excreted in the the urine.
If infected with bacteria, the bacteria
digests the urea and breaks it down
into ammonia. Ammonia is toxic to
the cells of the bladder wall causing
inflammation. Proteins are released
to form a matrix which the crystals
use to form a stone.
The general rule in dogs is :
No infection
No stone
85% of canines with struvite stone
occurrence occurs in females.
Predisposed breeds include beagle,
schnauzer and cocker spaniels. The
average age for stone occurrence is
2 ½ years.
Magnesium ammonium
phosphate
Magnesium ammonium
phosphate
Calcium oxalate dihydrate crystals
appear as small squares containing
an X.
Calcium oxalate monohydrate may
be shaped like a dumb bell or they
may be elongated and pointed at
each end, resembling a picket fence
slat.
Calcium oxalate crystals are
formed in acidic and neutral urine
and may be seen in small numbers
normally in dogs.
The urine of animals poisoned
with ethylene glycol often contains
large numbers of the monohydrate
crystals.
Large numbers of calcium
oxalate crystals seen in the urine
may indicate a predisposition to
oxalate urolithiasis.
73% of canines affected by calcium
oxalate crystals and stones are male.
Breeds predisposed include,
schauzer, lhasa, yorkie, poodle, shih
tzu, bichon. The average age is 5 –
12 years
Calcium oxalate stones can not be
dissolved by diet and must be
surgically removed.
50% of animals who undergo
cystotomy sx will redevelop
stones within 3 years.
Calcium phosphate crystals
assume various forms including
the rosette and pointed finger
forms. They appear most often in
alkaline urine.
Uric acid crystals appear yellow to
yellow brown. The most common
shapes seen are diamond,
rhomboid or rosettes. These
crystals are very uncommon in
small animals but are seen in
dalmations.
• We eat purines when we eat meat and drink them
when we drink coffee and our livers convert them
ultimately into something called “Allantoin” which
is readily soluble in water and easy for us to unload
in that waste/water mixture known as urine.
• Dalmatians just cannot seem to convert uric acid to
allantoin; the process described above never gets
past the uric acid stage. Dalmatian liver cells simply
cannot absorb uric acid which is where the
conversion to allantoin ought to take place.
Dalmatians must excrete uric acid in their urine and
the problem is that the stuff just is not that water
soluble. Being unable to convert uric acid to
allantoin is the main predisposing factor to uric acid
stone formation and accounts for why 80% of uric
acid bladder stones come from Dalmatians.
Ammonium urate crystals are seen
in slightly acidic, neutral and
alkaline urine. The shape of these
crystals is called the “thorn apple”
These crystals are not common but
are frequently observed in dogs
with portal vascular anomalies.
Common breeds are Dalmations
and English Bulldogs
Cystine crystalluria is not a
normal phenomenon. These
crystals may develop in animals
with metabolic disorders
Cholesterol crystals are seen in the center of this field with
squamous epithelial cells on either side. Cholesterol crystals
are found in acid or neutral urine. They appear as regular or
irregular transparent plates. They may occur singly or in large
numbers. Usually one or more corners are cut off or notched,
justifying their description as "stair step crystals". They are
not commonly seen and are always considered pathological.
They can be found in various renal diseases.
Tyrosine crystals are not normally found in urine. They are
products of protein metabolism and appear in urine of animals
with tissue degeneration or necrosis (acute liver disease) They
are present only when urine is acid. They are colorless to
yellowish brown, needle shaped crystals and have a fine silky
appearance. The needles may be single or arranged in sheaves
or rosettes. Tyrosine crystals usually appear in urinary
sediment together with leucine crystals
Leucine crystals are not normally found in urine They appear in
urine in association with tyrosine and are manifestations of the
same clinical conditions. When found, leucine crystals are in
acid urine in the form of spheroids with concentric striations.
They are dense, highly refractive and appear as yellowish
brown bodies.
Cystotomy :