Urine collection, processing and physical examination Flashcards
Specimen Storage and Handling for urine
Diagnostic tests are of little value if the sample has not been collected or stored properly
It can lead to an incorrect diagnosis and treatment, or a condition can be missed completely
Appropriate urine containers
Can be disposable or reusable
Must be dry and free of chemical residue
Transparent containers are useful for the physical examination of the urine but are not essential
When purchasing containers, they should be readily available, sturdy, leak-proof and inexpensive
If storage or shipment is required, a tight-fitting lid is essential
4 ways to collect urine
Natural micturition (aka free catch)
Manual expression (still considered to be free catch)
Catheterization
Cystocentesis
Sample preservation
Urine is considered unstable so should be looked at as soon as possible (within 30-60 minutes)
The longer the sample sits at room temperature, the more alkaline the sample will become
Record when the sample was collected and when it was analysed
When to refrigerate urine
Refrigerate the sample if it is not going to be processed within 30 minutes
Use an opaque or amber container, keep away from light
Make sure it has a tight-fitting lid to prevent spilling,evaporation and contamination
Refrigeration is the most common form of short-term storage and preservation–can be used for up to 12 hours after collection
What to do once a urine sample has been refrigerated
Samples need to be warmed to room temperature before analysis
USG will be increased if the urine is cold Enzyme- based reactions are decreased if the urine is cold
Crystals can form in refrigerated samples–may not dissolve when the urine is brought to room temperature
Abnormalities found on stored samples should be retested on a fresh sample
Samples that require storage for more than 12 hours can be preserved by adding one of the following:
1 drop 40% formalin to 29.6 ml of urine
Must do chemical analysis first
Toluene sufficient to form a layer on top of the sample
One thymol crystal
One part 5% phenol to nine parts urine
Unfortunately, no single preservative agent is satisfactory for all routine U/A tests
Physical Examination of Urine should include
Before the chemical tests or a microscopic evaluation is performed, the physical properties of the urine should be noted. These include:
Urine Volume
Color
Clarity/Transparency
Odor
Specific Gravity
How to measure urine volume
Owner often provides this information
May mistake pollakiuria for polyuria
Taking an accurate history will aid in differentiating between the two
Urine production is influenced by several variables including:
Species
Body weight and size
Diet
Fluid intake
Physical activity
Environmental factors such as temperature and humidity
Polyuria is
The formation & elimination of excessive amounts of dilute urine
Often accompanied by polydipsia
Polyuria in the presence of dehydration occurs when the kidneys are unable to conserve water despite the body’s dehydrated state
May be caused by renal failure, diabetic ketosis, pyometra and some liver disorders
What are the two types of polyuria
Pathological
Physiological
Pathological polyuria is caused by
Occurs with many disease conditions including diabetes insipidus, diabetes mellitus, CRF, ARF, nephritis, pyometra, hepatic disorders
Physiological polyuria is caused by
Due to high fluid intake, high salt intake, fluid therapy, or medications (steroids and diuretics)
Oliguria is
Decreased urine formation by the kidneys and/or decreased elimination of urine from the body
Oliguria is caused by and treated by
Can be physiological as a result of:
Decreased water consumption
Exposure to a warm environment
May be a response to dehydration, fever, vomiting…
The situation results in a small volume of urine that is usually very concentrated
It is reversible if the primary problem is corrected
Colour of urine
Normal urine colour varies from nearly colourless to a deep amber
The color of the urine is usually related to the degree of urinary concentration
Though it may also be due to the presence of abnormal constituents within the sample
An animal’s first urination of the day is usually the most concentrated sample of the day, and therefore the darkest in color
You must report urine colour as part of the urinalysis
A number of conditions result in a change the color of urine
Evaluate urine color by placing the sample in front of a white background
Red or red-brown urine means
Most often due to hematuria or hemoglobinuria
Fresh hemorrhage of the urinary tract
Must confirm presence of RBCs with microscopic exam
Proteinuria accompanies this colour change
Brown or brown-tinged urine means
Myoglobinuria
Proteinuria accompanies this colour change on the chemical analysis of the urine
Yellow-brown/green colour urine is caused by
Produces a greenish-yellow foam when shaken
Usually due to bilirubinuria
Due to liver disease, hemolysis or the presence of bile
Bilirubin is usually confirmed by microscopic or chemical means
What can drugs in urine look like for colour
Can produce variations in colour from pink to green or blue
Therefore, an adequate history must be taken
Clarity/Transparency is determined by
Clarity is a reflection of the number of particles present in the urine
How clear the urine is, NOT the color of the urine
An increase in turbidity may be caused by the presence of mucus, cells, vaginal secretions, sperm, crystals, bacteria, fat, calcium compounds, fecal and other contaminants
The underlying cause is determined by microscopic examination of the urine
How does urine clarity change by species
rom species to species
Canine–normally clear
Feline- normally slightly cloudy
Horses– normally cloudy
Due to the presence of calcium carbonate crystals and mucous
Rabbits-normally turbid with a milky appearance
Due to the presence of calcium carbonate crystals
How to tell transparency of urine
When evaluating transparency, it may be easiest to do so by placing a sheet of paper with lettering behind the sample to evaluate the urine
Turbid/flocculent urine looks like
Turbid/Flocculent–cannot see through the sample, suspended particles are present in the sample and may be visible with the naked eye
Urine will become more turbid upon sitting due to bacterial growth and crystal formation
Slight foaming is normal in urine but will be increased when urine protein levels are elevated
What does cloudy urine look like before and after centrifuge
cannot read through the sample, objects are blurred, sample usually contains large particles
Significant amount of sediment is present after centrifugation
What does horse urine look like after sitting
Horse urine will become brown and opaque upon standing while freshly voided urine is dark yellow and turbid
Odour of urine
Male cats, pigs and goats produce strong smelling urine
Odor is often increased when urine is concentrated
Often not a highly diagnostic test
What can the smell of urine tell you
Strong/ammonia odor: concentrated samples
Little to no odor: dilute samples
Foul odor: may be noted with bacterial growth
Sweet smell: may be an indicator of the presence of ketones in the urine
Specific gravity is
It is the ratio of the density of urine compared to the density of distilled water
Because it is a ratio, there are no units
It is an estimate of the ability of the kidney tubules to concentrate urine
why do we test urine SG
Provides valuable information regarding the patient’s hydration status and renal concentrating ability
How to test urine SG
Dipstick method is NOT accurate so we test separately with a refractometer
Must be performed on the supernatant if the sample is turbid or if it is hard to see the line on the refractometer
Affected by temperature– so sample must be at room temperature
Normal values for urine specific gravity vary between species
What does the urine Sg tell u
A USG below the normal range for that species means that the urine is dilute
Hyposthenuria: USG is between the normal range and the isosthenuric range
Isosthenuria: when USG is approaching that of the glomerular filtrate (1.008-1.012)
What is SG dependent on
Urine concentration depends upon water intake, diet, electrolyte balance, age, renal concentrating ability and hydration state (including fluid administration)
Must look at all aspects of the animal to interpret the results, including hydration status, BUN and creatinine levels
The USG value will fluctuate throughout the day and from day to day
USG dog
> 1.030
USG cat
> 1.035
USG horse
> 1.025
USG of cattle
> 1.025
