Urinalysis
Laboratory Procedures Ch. 5
Urinalysis
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This test is often part of an
initial data base for case
work up of a clinically ill
patient.
It is a very useful indicator of
renal function, and should be
performed on any animal
suspected to have renal
disease or urinary tract
pathology
Urinalysis

A urinalysis consists of gross examination of
urine, a specific gravity (SG), chemical
analysis, and sediment evaluation.

Equipment required : clean glass or plastic
collection container, a centrifuge and conical
centrifuge tubes, chemical reagent strips,
clean glass slides and coverslips, a
refractometer and microscope. A sediment
stain is recommended.
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The best samples for urinalysis are morning
samples. These are the most concentrated.
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Urine samples should be analyzed within 30
minutes to 1 hour of collection.
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Physical properties of urine include volume ,
color, odor, transparency, and specific
gravity.
Collection for analysis
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There are several different methods of
collection for urinalysis and each has its
benefits and draw backs.
Collection methods will often be dictated by
the information that you are looking to
gather.
Analysis of urine samples should be
performed only in samples taken before
administration of therapeutic agents.
Midstream, voided or “Free Catch”
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This collection method is often
easiest for the animal but can
be quite difficult for the
collector.
Collection is made into a
container directly from the
patient.
This collection method will
obviously contain
contamination
Manual Expression:

This collection method is most often
performed on small dogs and cats. It is
sometimes difficult, and can result in
trauma in the form of red blood cells in
the urine. This method will also contain
contamination from the lower urinary
tract
Catheterization

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Catheterization is the
insertion of a polypropylene
or rubber catheter into the
bladder by way of the urethra
This test can be used on
male dogs for the
assessment of urethral
patentcy and upper urinary
tract infection. This method
often results in iatrogenic
presence of red blood cells in
the urine.
Lubricate the catheter
Cystocentesis:
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This method requires penetration of
the bladder through the body wall
and can be accompanied by
minimal bleeding. This is the best
way to analyze the upper urinary
tract for infection.
Use a 22 or 20 gauge needle by 1
inch or 1½ inches and a 10 ml
syringe
For male dogs, insert the needle
caudal to the umbilicus and to the
side of the sheath
For female dogs and cats insert the
needle on the ventral midline caudal
to the umbilicus
Volume
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Normal 24 urine production for dogs and
cats is 20-40 ml/kg. An average sized
saddle horse may produce between 5
and 15 L of urine in 24 hours.
An increase in this volume is termed
polyuria and may be due to physiological,
pharmacological or pathological causes.
Decreased urine volume is called
oliguria, and occurs in dehydration, renal
failure, or urinary blockages.
No urine is called anuria, and is an
emergency condition that may be due to
renal failure, urinary blockage or ruptured
bladder.
Color
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Urine color will vary between species,
but it is normally some shade of yellow
depending on the concentration.
Abnormal color changes in the urine
could be due to drugs, increased
urinary pigments or red blood
cells. Red to reddish-brown could be
due to either hematuria,
hemoglobinuria, or myoglobinuria.
Occasionally, unusual colors may be
caused by dyes associated with food or
drugs.
urine sample exhibiting
hematuria
Turbidity


Urine is normally transparent in
most animals, except for the
horse. The horse has a thick
viscous urine that is cloudy on
examination.
In small animals, turbidity
suggests the presence of cells,
casts, or crystals. Often
refrigeration will propagate the
sedimentation of crystals in the
urine, producing a cloudy
appearance. This is usually of no
significance
The sample on the left is
exhibiting turbidity. The
sample on the right is a
normal color and clarity for
canine urine
Odor

Urine has a characteristic smell that varies slightly by
species and concentration of the sample.
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A particularly foul odor may occur in the presence of
bacteria. Thus, strong smelling urine is common in cases of
cystitis.
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Ketonuria produces a very sweet smell as does glucosuria.
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Sweet smelling urine is commonly associated with diabetes
mellitus.
Specific Gravity
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Specific gravity measures the concentrating ability of
the kidney tubules. It is the ratio of the weight of
urine to the weight of an equal volume of water.
Normal values range from 1.001-1.060 in most of
our domestic animals. If the kidneys are unable to
concentrate urine the specific gravity will approach
that of the glomerular filtrate, at 1.010.
A small drop of the urine sample is placed under the
slide on the top of the scope, and the measurement
is made by looking through the eye piece to read the
value indicated.
The Chemical Analysis
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A chemical analysis of urine is performed
using a commercial dip stick reagent strip.
If the sample is turbid, the chemistry tests
are done on the supernatant.
What is evaluated on chemical
analysis?
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Protein
Glucose
Ketones
Blood
Bilirubin
Urinary pH
pH
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Urine pH will be affected by many things
including the diet, handling of the sample,
and acid-base balance of the animal. An
alkaline pH is most indicative of an
infectious process. Normal pH is between 6
and 8 for most animals depending on their
diet.
Glucose
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In the normal animal there should not be
glucose in the urine.
If glucose is present, it is a classic response
to hyperglycemia and should instigate an
investigation into the possibility of diabetes in
the patient.
Ketones
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In the normal animal there will
be no ketones in the urine. An
animal that is undergoing fat
metabolism or is deficient in
carbohydrates will have
ketones in the urine. Slight
ketonuria should be expected
in malnourished animals. A
ketonuria also frequently
accompanies diabetes
mellitus.
Bilirubin

Bilirubinuria increased concentrations of
bilirubin due to biliary obstruction,
cholestasis, or increased bilirubin production
secondary to hemolysis.
Blood
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There should not be any blood in the
urine of a normal animal. Most test
strips cannot differentiate between
red blood cells, hemoglobin, or
myoglobin, thus some care should be
taken in interpretation.
Hematuria is also evaluated in urine
sedimentation microscopically and is
reported as cells per high power field
(or HPF). Remember that collection
methods may also cause blood to
appear in the urine. Other causes of
hematuria include infection,
neoplasia, or trauma.
Protein
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Urine normally contains a small amount of
protein, which is due to normal leakage and
secretion from the urinary tract lining. This
“normal” amount of protein will not show + on
the dipstick.
Proteinuria is an excess of serum proteins in
the urine. This is an important factor of renal
disease.
Proteinuria can also be found in
glomerulonephritis, congestive heart failure,
and renal ischemia of all kinds.
Sediment
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Urine sedimentation may contain cells, casts and
crystals and is examined microscopically after
centrifugation of a urine sample.
A very small amount of all of the above sediments is
normal. Concern begins when any of these
components is significantly elevated.
There are many different crystals, cell types, and
casts that may be found in the urine of animals, and
it varies from species to species.
Urinary Crystals
Crystals cont’d
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pH dependant
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May indicate a urolith (bladder stone)
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May lead to urethral obstruction
Calcium Oxalate crystals
Acidic urine (6.5 and below)
Calcium Oxalate crystals in a slightly
different configuration
Struvite Crystals / Triple Phosphate
Neutral to Acidic (7.0 and above)
Struvite Urolith
Casts
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Casts are elongated structures composed of
protein from plasma and mucoprotein from the
renal tubules.
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In general, they form in the distal tubules, in
which the urine is more concentrated and acidic.
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Any structures that happen to be in the tubules
at the time the casts form (RBCs, WBCs or
epithelial cells), become embedded in the casts.
Casts
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The presence of increased numbers of casts
helps to localize the renal disease to the
tubules, but the numbers to not necessarily
correlate with the severity of the disease.
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The five main types of casts are :
Hyaline, Cellular, Granular, Waxy and Fatty
Cast Compilation
The image below represents different
casts seen in urine at the same
magnification and lighting. Shown are
hyaline, fatty, granular and waxy casts.
Hyaline casts can be quite difficult to see
in wet preparations of urine sediments
with light microscopy, even with the
condenser of the microscope racked
down. They are much easier to visualize
using phase contrast, however phase is
usually not available on most
microscopes. They become more visible
with regular light microscopy if fat sticks
to the protein matrix (Tamm-Horsfall
mucoprotein) that makes up the hyaline
cast (image B) or particulate material
from degenerating cells is present within
the cast matrix (image C). Cellular casts
have distinct cells within the protein
matrix - if the cells are of epithelial origin
(i.e., not WBCs or RBCs), they are
called epithelial casts (images D and E).
As cells within the protein cast matrix
break down, the cast becomes coarsely
(image E and F) then finely granular
(image G). Waxy casts are the final
stage of cast degeneration (usually
originating from cellular and granular
casts). Compared to hyaline casts, they
are readily observable because they
have a smooth appearance, no internal
texture, and are more refractile than the
surrounding urine.
Legend: A: Hyaline cast; B: Fatty cast;
C: Hyaline to finely granular cast; D:
Cellular cast;
E: Cellular to coarsely granular cast; F:
Coarsely granular cast; G: Finely
granular cast; H: Granular to waxy cast,
I: Waxy cast.
A: Hyaline cast
B: Fatty cast
C: Hyaline to finely granular
D: Cellular cast;
E: Cellular to coarsely
granular
F: Coarsely granular cast;
G: Finely granular cast
H: Granular to waxy cast
I: Waxy cast.
Hyaline Casts
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Colorless, homogenous, and semitransparent. May be
difficult to see unless the light is reduced. These casts
occur in health and also in association with mild
glomerular leakage.
Cellular Casts
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Contain recognizable cells embedded in the
protein matrix.
Cellular casts may be epithelial cell casts that
contained sloughed tubular epithelial cells,
RBC casts that indicate renal hemorrhage, or
WBC casts that indicate renal inflammation of
pyelonephritis.
RBC Cast
WBC Cast
Granular Casts
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Casts derived from degenerating cells or
cellular casts.
Characterized by a nonspecific granular
matrix and are designated as either coarsely
or finely granular.
This is the most common type of cast found
in animals.
Granular casts
Coarse
Fine
Waxy Casts
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Homogenous and wide.
Usually has distinct blunt or squared ends.
Indicate a more chronic renal lesion.
Fatty Casts
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Contain fat globules from degenerating
tubular epithelial cells.
Most common in cats because of high lipid
content of feline tubular epithelium.
Bacteria / Microorganisms
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Bacteria in a voided sample are usually not
clinically significant = contamination from
distal urinary tract.
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Bacteria in a catheterized or cystocentesis
sample = clinical significance.
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Bacteria in a sample is most often correlated
with the presence of WBC.
Rod bacteria may appear singly or in chains. Cocci bacteria may also
be present.
Bacteria Video
YouTube - Bacteria In Urine
How to Microscopically Examine
Urinary Sediment
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A sample of well-mixed urine (usually 10-15 ml)
is centrifuged in a test tube at relatively low
speed (about 2-3,000 rpm) for 5-10 minutes.
The supernatant is decanted and a volume of
0.2 to 0.5 ml is left inside the tube. The sediment
is re-suspended in the remaining supernatant by
flicking the bottom of the tube several times. A
drop of re-suspended sediment is poured onto a
glass slide and coverslipped. Another drop is
stained using urinary sediment stain.
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The sediment is first examined under low
(10X) power to identify most crystals, casts,
squamous cells, and other large objects. The
numbers of casts seen are usually reported
as number of each type found per low power
field (LPF). Since the number of elements
found in each field may vary considerably
from one field to another, several fields are
averaged.
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Next, examination is carried out at high (40X 100X) power to identify crystals, cells, and
bacteria. The various types of cells are usually
described as the number of each type found
per average high power field (HPF). Example:
1-5 WBC/HPF.
RBCs
Red Blood Cells
 Red cells may also contaminate the urine
from the vagina in menstruating dogs or from
trauma produced by bladder catherization.
Theoretically, no red cells should be found,
but some find their way into the urine even in
very healthy animals. However, if one or
more red cells can be found in every high
power field, and if contamination can be ruled
out, the specimen is probably abnormal.
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RBC's may appear normally shaped, swollen
by dilute urine (in fact, only cell ghosts and
free hemoglobin may remain), or crenated by
concentrated urine. Both swollen, partly
hemolyzed RBC's and crenated RBC's are
sometimes difficult to distinguish from WBC's
in the urine. In addition, red cell ghosts may
simulate yeast.
RBC Cast
White Blood Cells
 Pyuria refers to the presence of abnormal
numbers of leukocytes that may appear with
infection in either the upper or lower urinary
tract or with acute glomerulonephritis.
Usually, the WBC's are granulocytes.
 If two or more leukocytes per each high
power field appear in non-contaminated
urine, the specimen is probably abnormal.
Leukocytes have lobed nuclei and granular
cytoplasm.
WBC Cast
Epitheleal Cells
Renal tubular epithelial cells, usually larger than
granulocytes, contain a large round or oval nucleus and
normally slough into the urine in small numbers.
However, with nephrotic syndrome and in conditions
leading to tubular degeneration, the number sloughed is
increased.
Represent possible contamination of the
specimen with skin flora. Large polygonal with small
nuclei.
Transitional epithelial cells from the renal pelvis, ureter,
or bladder have more regular cell borders, larger nuclei,
and smaller overall size than squamous epithelium.
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Squamos Epitheleal
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Transitional Epithelial (A)
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Renal Tubule Epithelial (B)