Introduction to Urinalysis
Laboratory Procedures
Urinary System
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Designed to maintain a balance between
fluid, electrolytes, and acid-base homeostasis
by selectively eliminating waste products
from the body.
Urine is formed through glomerular filtration,
tubular reabsorption, and tubular secretion
(remember everything you were taught in
A&P).
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These are influenced by hormones
Medical Terminology
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Pollakiuria
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Polyuria
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Decrease in the formation or elimination of urine
Anuria
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Increased urine output or production
Oliguria
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Frequent urination
Complete absence of urine formation or elimination
Dysuria
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Difficult urination
Urinalysis
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Urine collection can
be accomplished
through mid-stream
free catch, manual
expression,
catheterization, and
cystocentesis.
Advantages to Urinalysis
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Fast
Simple
Inexpensive
Provides useful information (urinary tract
and/or other body systems)
Voided Urine Sample
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Easiest to obtain
May be contaminated
from distal genital tract
Not satisfactory if
examining for bacteria.
Voided Urine Sample Collection
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Use a clean container
Wash prepuce or vulva (when possible)
Try to collect mid-stream urine
Disadvantages to Voided Sample
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Contamination
Difficult in cats
May be difficult in easily scared dogs and
short breeds
Expressing the Bladder
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Use steady gentle pressure
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Will feel like a balloon or ball under your hands.
Make sure you are expressing in a squeezing
motion where you are forcing urine down urethra.
Wash external genitalia
Contamination from lower urinary tract/genital
tract is a concern.
DO NOT DO MANUAL EXPRESSION
WHEN THERE IS AN URETHRAL
OBSTRUCTION!!!
Urinary Catheterization
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Act of placing a catheter through urethra into
bladder
Advantages:
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Less possibility of contamination from lower
genital tract.
Helpful in obese animals when bladder is difficult
to palpate
Disadvantages
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Trauma to sensitive urethral mucosa
Possible contamination
Cystocentesis
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Act of obtaining a urine sample via a needle
and syringe directly from the bladder
Advantages
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Sterile sample
Disadvantages
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Difficult to obtain in obese animals
Trauma to organs if not done correctly
Urine Sample Preservation
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Analyze all urine within
30 minutes if possible
May refrigerate for 6-12
hours if needed
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Bring to room temperature
before anlaysis
Morning samples are
more concentrated
If allowed to stand at
room temperature, may
get false results.
Physical Characteristics of Urine
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Color
Transparency
Odor
Specific gravity
Volume
Urine Color
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Normal color is due to pigments called
urochromes
Normal: light yellow to amber color
Abnormals:
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Red: blood (hematuria)
Reddish-brown: Hemoglobin or Myoglobin
Dark yellow-brown: Bilirubin (bilirubinuria)
Orange-Reddish brown: Normal in rabbits
Urine Transparency
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Clear vs. Cloudy
Cloudy could indicate increase cells, mucus,
casts, crystals and bacteria.
Horses and some rabbits have cloudy urine
due to high content of mucus and calcium
carbonate crystals.
Urine Odor
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Not Very diagnostic
Strong odor may suggest bacterial production
Male cats, goats, and pigs have a very strong
urine odor
Urine Specific Gravity
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Measure urine concentration which is
dependent on the number, molecular size,
and weight of urine solutes
Measures the density of urine as it compares
to water
Specific gravity of water is always 1.000
“Normal” Urine Specific Gravities
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Man: 1.003-1.037
Dog: 1.013-1.030
Cat: 1.013-1.050
Horse: 1.015-1.045
Methods of collecting a urine specific
gravity
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Refractometer
Reagent strip
Urinometer
Causes of Altered Specific gravity
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Increased specific gravity
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Dehydration
Increase fluid loss
Decreased water intake
Decreased specific gravity
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Kidney disease
Excessive water
Pyometra
Some drugs
Urine Volume
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Influenced by several factors
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Water intake
Size of animal
Species of animal
Crystals
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The presence of crystals in the urine is called
crystalluria.
There are many types of crystals that can
form in urine, we are going to cover just a
few. (More to come in Clinical Pathology!)
Crystalluria may or may not be of clinical
significance.
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Certain crystals form as a result of elements being
secreted into the urine by normal renal activity.
Crystal formation
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Crystal formation depends on the pH of the
patients urine.
Some crystals form in acidic urine, while
others form in basic or neutral urine.
If a urine sample is allowed to stand and cool
to room temperature, the number of crystals
in the urine will increase because the material
that forms the crystals is less likely to
dissolve at cooler temperatures.
Types of crystals
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Triple phosphate
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Includes Struvite, and Ammonium Magnesium
Phosphate.
While their name may be interchanged, these
crystals have slightly different composition.
Generally appear as “coffin lids” or roof-tops
Form in alkaline to slightly acidic urine.
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May take a fern-leaf shape if urine has high
concentration of ammonia
Calcium Oxalate Dihydrate
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Generally appear as small squares with a
visible “X” across the top of the crystal.
Most often form in acidic and neutral urine.
Are commonly seen in small numbers in dogs
and horses.
If seen in large numbers, can indicate calculi
formation.
Calcium Oxalate Monohydrate
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May be small and “dumbbell” shaped, can
also appear as a slat from a picket fence.
Generally form in any pH urine, but are a key
indicator if an animal is experiencing ethylene
glycol toxicity!
Uric Acid/Ammonium Urate Crystals
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Uric Acid crystals often appear as yellowbrown “rosettes” or as diamond-shaped
“plates”.
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Ammonium Urates often appear as “thornapples”
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Can form in any pH urine!
Generally form in neutral to alkaline urine.
Are very rarely seen in dogs and cats.
(Except Dalmatians!!)
Uric Acid Crystals
Ammonium Urate Crystals