Transcript Performing the Urinalysis

Performing the Urinalysis
Laboratory Procedures
Analyzing the Urine Sample
 A complete urinalysis usually involves
3 steps.
 1. Checking and recording the physical
characteristics of the urine
 2. Performing a chemical analysis using a
multi-test dipstick
 3. Centrifuging a small portion of the
sample and examining the sediment
under a microscope
1. Checking and recording the
physical properties of the urine
 Physical properties include:
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Color
Transparency
Odor
Specific gravity
Volume
2. Chemical Analysis
 Many chemical tests can be performed on a small
quantity of urine by using a dipstick
 Each pad on dipstick is designed to test for a
particular substance in the urine.
 When the urine comes in contacts with the reagents,
a chemical reaction will cause a color change based
on the amount of the substance in the urine.
 Color is compared to chart, and approximate amount
of substance in urine can be determined
 Several brands of dipstick exist.
Chemical analysis
 Certain drugs and medications may
interfere with chemical tests.
 Be sure to know any medications
animal is currently receiving when
performing a urinalysis.
Components on the Dipstick
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Urine pH
Protein
Glucose
Ketones
Bilirubin
Urobilinogen
Blood
Nitrites
Urine pH
 Number of how acidic or alkaline the urine is
 pH is affected by diet.
 Plant diets can cause alkaline urine
 High protein diets can cause acidic urine
 Small animal pH is usually acidic
 In general dog and cat urine pH is 6-7
 Large animal urine is usually alkaline
 Other factors may affect urine pH
 Fever
 Starvation
 Certain drugs
Protein
 Healthy animals will usually not have any
protein in their urine although in some
cases trace amounts can be found in
concentrated dog and cat urine.
 The urine protein level must be interpreted
along with the Urine specific gravity.
 Small amounts of protein are more
significant in dilute or unconcentrated
urine.
 Protein may be lost in the urine due to
glomerulopathies, inflammation, or
hemorrhage.
Glucose
 If the sugar in the blood is
significantly higher than normal,
some excess may be found in the
urine.
 Normal dog and cat urine should be
negative for glucose.
 In some cases if the urine is not run
immediately, false glucose readings
may occur.
Ketones
 Ketones are the substances formed in the
body during the breakdown of lipids.
 Normal pet urine should be negative for
ketones
 When excess amounts of ketones are
formed, their levels rise in the blood and
then are released in the urine.
 Can cause CNS depression and acidosis
 May result in ketonuria caused by:
 Starvation
 Diabetes
Bilirubin
 Pigment made by the liver from dead or
dying red blood cells.
 Small amounts may sometimes be found in
healthy dogs.
 Dogs can conjugate bilirubin in their kidneys, so
small amount may be insignificant.
 Bilirubin found in cat urine is a concern and
can be a sign of liver disease, bile duct
obstruction, or hemolysis.
Urobilinogen
 Compound formed from bilirubin by
intestinal tract.
 Normal dogs and cats have small amounts
of urobilinogen in their urine.
 Results from dipstick are not considered
very accurate and may be difficult to
interpret.
 Usually recorded as “normal” or
“abnormal”.
Blood
 Healthy pets may have a
few red blood cells in their
urine, but greater than ~5
cells per field may indicate
a problem.
 Hematuria can be due to a
number of causes:
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Trauma
Urinary Tract Infection (UTI)
Bladder Stones
Blood Clotting Problems
Blood cells in the Urine
Nitrites
 May be produced by the bacteria
present in some infections
 Test often shows a “false negative”
and is considered inaccurate in pets.
 However, if positive, should examine
sediment closely for bacteria.
Examining Urine Sediment
 After urine sediment is centrifuged
(generally about 5 minutes), the top
portion of the liquid is poured off and the
sediment is resuspended and examined
microsopically.
 Indications for sediment exam include:
 Provides additional information
 A form of cytology
 Must be interpreted with other clinical data,
including physical and chemical composition of
the urine.
Urine Sediment Exam Procedure
 1. Collect urine in a clean container
 2. Throughly mix specimen and transfer 35 ml volume to a centrifuge tube
 3. Centrifuge for 3-5 mins
 4. Pour off supernatant
 5. Leave approximately 0.5 ml of
supernatant
 6. Resuspend urine sediment by tapping
tube or flicking it w/ your finger.
 7. Examine a stained or unstained
sediment. (Or both!)
Potential Sediment Elements
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White blood cells
Red blood cells
Lipid droplets
Bacteria
Crystal
Casts
White blood cells
 Larger than normal numbers of white
blood cells may indicate inflammation
from a bladder or kidney infection.
Lipid Droplets
 Are common in the sediment of urine,
especially in cats.
 Number and size may vary
 Should not be confused w/ air
bubbles or RBC’s. They will be in
focus when other structures are
not.
Bacteria
 Sediment is examined for presence of
bacteria
 Small amounts may be due to
contamination, large amounts may
indicate bladder infection (especially
if sample is obtained via
cystocentesis).
 A urine culture and sensitivity may
indicated with large amounts of
bacteria.
Crystals
 Made up of minerals and can
sometimes be found in the urine.
 Under certain conditions, crystals can
clump together to form bladder
stones (uroliths).
 The pH of the urine may influence the
type of crystal development
 Some animals and species are more
predisposed to crystal and stone
formation.
Common Crystal
Types
 Struvite
 Calcium Oxalate
 Ammonium Urate
Casts
(These will be covered in depth in Clin-Path!)
 Urine Casts are small cylinder-shaped formations of
cells and debris from inside the tubules of the kidneys
 Presence and composition of casts can indicate kidney
function
 Types of casts:
 Hyaline
 Granular
 Waxy
 Fatty
 Cellular
 Mixed
 Bile stained
Specific Gravity
 Measures the concentrating ability of the
kidney.
 Done with a refractometer
 There may be a spot on the dip-stick
for SG, however in animals, these are
not valid results.
Specific Gravity “normals” p. 158 Lab bk
 “Normal” values in dogs is between 1.001-1.060
 “Normal” values in cats can range from 1.001 – 1.080
 There is no set “normal” value in animals, however the
following guidelines should be used:
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SG: below 1.008 is said to indicate dilution (hyposthenuric)
SG: 1.008-1.012 is said to be fixed or isosthenuric (same SG as
plasma)
SG: 1.013 – 1.030 is considered normal if no dehydration
suspected.
SG: above 1.025 implies renal tubule concentration ( in cats, this
can indicate renal disease)