Chemical evaluation or urine Flashcards
How to perform a chemical evaluation of urine using reagent strips
Evaluation is semi-quantitative when using reagent strips
The strips have pads that are impregnated with chemicals
When urine is applied to them, a colour change occurs
Must adhere to expiry date of the urine strips to avoid false negative results
Keep the lid of container tightly sealed to prevent color changes due to environmental conditions
Don’t touch the pads with your fingers
The strips must be stored at room temp
They should be fully immersed (dipped) in the urine with excess being wicked away by tilting the long edge on a paper towel
Can pipette the sample on the test strip but must make sure that the pads are fully saturated
Strips can be for individual tests or for multiple tests
Must read colour changes at appropriate times
Use test strips that are specifically made for animals
The following test results have limited reliability on reagent strips
Leukocyte tests- verify on microscopic exam
Specific gravity
Urobilinogen
Nitrates
pH of urine is tested by
Urine must be fresh and at room temp for testing
The pH tends to increase the longer the sample is sitting at room temp
Can be measured with the dipstick or a pH meter
The pH meter is more accurate, however the strip gives sufficient results
Less than 7 is acidic, greater than 7 is alkaline
pH will vary depending on the animals diet
Forage based diet→ alkaline urine
High protein, cereal based diet→ acidic
Meat based diets → acidic urine
Dogs and cats have acidic urine in health with a normal pH of 6-7
The pH of dog and at urine tends to increase shortly after eating due to “alkaline tide”
Herbivores have alkaline urine in health
What will the pH of urine tell you
The pH of the urine will help you to identify structures present in the urine sediment
Struvite crystals tend to form in alkaline urine
Calcium oxalate, cysteine and uric acid calculi tend to form in acidic urine
How to use pH to your advantage
Urine pH is influenced by diet which can use to the animals benefit
Prescription urinary diets- prevent the recurrence of stones and crystals by acidifying the urine
These diets also have increased salt content to increase drinking, thus diluting the urine
They also minimise pH fluctuations during alkaline tide
Increased urine pH may be caused by
Urease-producing bacteria will cause urine to become alkaline
This is possible with a bladder infection or if urine is sitting for extended periods at room temp
Stress and excitement can case an increase in urine pH
Alkalosis
Urine retention
Medications
A reduction in urine pH may be caused by
Fever
Starvation
Acidosis
Excessive exercise
Medications
Proteinuria is
an abnormal increase in quantity of protein in the urine
Protein in urine
Dogs and cats normally have zero to trace amounts of protein in their urine
Collection method dependant
The presence of proteinuria should be interpreted based on quantification, urine collection method, microscopic examination of the urine and USG
Dilute urine can give false-negative results
Proteinuria may be caused by the following conditions
Urinary tract haemorrhage or inflammation, renal tubular degeneration, exercise, fever, or due to contaminants form the genital tract, trauma from urinary catheterization, manual expression or cystocentesis
When can change the results for proteinuria
False + protein tests can be the result of extremely alkaline urine samples
The presence of cells and casts in the urine can elevate protein levels
The supernatant should be retested
Urine dipstick tests primarily test for albumin
Less sensitive to globulins
The test strip should never be allowed to sit in the sample, as there will be false + due to bleeding of buffers from one test pad to the other
Urine protein/creatinine ratio
Used to confirm whether the amount of protein present in the urine is significant or not
It eliminates urine volume and USG as variables
Can be done in house with some analyzers or as a referred out test
glucosuria/glycosuria is and most commonly occur when
the presence of glucose in the urine
Most commonly occurs when an animal’s blood glucose concentration exceeds the maximum renal tubular threshold
What does glucosuria do to the USG and when to evaluate it
Glucose in the urine should be evaluated along with blood glucose levels
Increased levels of glucose or protein will increase the USG
Glucosuria may be caused by
Diabetes mellitus- most common cause of glucosuria
Stress- possible in cats, but uncommon for stress to be severe enough to cause glucosuria
Postprandial effect after a high carbohydrate meal-uncommon
After receiving dextrose containing fluids
After a general anesthetic- rare
Rarely with other disease conditions
Ketones in urine and the reagent strips
The stips are only a screening test as certain ketones are not detected by the strips
Do detect acetoacetic acid and acetone
Do not detect β-hydroxybutyric acid
ketonuria means
the presence of ketones in the urine
Why do ketones get in the urine
Altered carbohydrate metabolism will cause the body to shift to fat breakdown as a source of energy
If there are insufficient carbohydrates available to aid i metabolizing the fatty acids, ketones will begin to appear in the urine
Causes of ketonuria
Diabetic ketoacidosis
Pregnancy toxemia in ewes
Ketosis in lactating dairy cows
Starvation
Anorexia
Low carbohydrate and high fat diet
Liver disease
when are ketones in the urine normal and what will cause a decreased amount
A low level of ketones in the urine can be normal in ruminants and in rabbits
Bacterial contamination of the sample will decrease the ketone level in the urine, therefore proper handling and storage are important
Bile pigments in urine are
Include bilirubin and urobilinogen
Bilirubin and urobilinogen
When is bile pigments in urine significant
Small amounts are normal in cattle and male dogs
Rarely found in pigs, sheep, horses or cats
Any amount in cats is considered abnormal
Usually due to liver disease, diabetes, aspirin toxicity, FIP, FIV or FeLV
What does bile pigment in urine look like
The urine will generally be a dark yellow colour
What causes bile pigments in urine
Causes include hemolytic anemia (most common cause in dogs), toxicities, liver disease or bile duct obstruction, obstructions of the upper intestinal tract
It is generally detected before jaundice is seen in the patient
How to test for bile pigments in the urine
Testing must be performed on a fresh sample that has been kept out of direct light and has not been refrigerated
Bilirubin is sensitive to both light and temp
Concentrated samples can give a false +
Yellow, yellow-green or brown foam on top of the urine sample when shaken indicate high bilirubin, urobilinogen or protein levels
Urobilinogen is
Urobilinogen is normal in urine
Screening tests are considered questionable
Urobilinogen is very unstable
Blood (hemoprotein) in urine tests
This test detects erythrocytes, hemoglobin or myoglobin
Hematuria is the presence of the intact RBCs in the urine
Hemoglobinuria is the presence of free hemoglobin in the urine
Myoglobinuria os the presence of myoglobin in the urine
Most test strips now will separate out erythrocytes form hemoglobin and myoglobin
Hematuria is and looks like
Intact RBC are present due to hemorrhage somewhere in the urogenital tract
Gives the urine a cloudy, reddish colour
Red pellet after the urine is spun down
When there are small amounts of blood that do not impart a colour change, it is referred to as occult blood
Will be picked up by a chemical analysis and sediment exam
Hemoglobinuria causes
Intravascular hemolysis- most common cause
Immune mediated hemolytic anemia, neonatal isoerythrolysis, incompatible blood transfusions
Contain heavy metals (copper), severe hypophosphatemia, postparturient hemoglobinuria in cattle, infections, toxins, hemolysis when cattle drink excessive amounts of water
When are ghost cells present in urine
If RBCs are present in very dilute or very alkaline urine, the cells will lyse and ghost cells may be present
What does urine with blood look like
The presence of hemoglobin in the urine gives it a clear red to red-brown colour
After centrifuging the urine will remain red in colour, no pellet is formed
Myoglobinuria is and looks like
Myoglobin is a protein that is found in muscle tissue
Myoglobinuria is caused by extreme muscle damage
Will be accompanied with increases in serum levels of CK, LDH, AST (muscle derived enzymes)
Seen in horses with exertional rhabdomyolysis
Gives urine a dark brown to almost black appearance
In low concentrations it may look similar to hemoglobinuria
The history and clinical findings are necessary to differentiate between eh two
Leukocytes in urine
The test strips give a large number of false negative results in most species
This test is considered unreliable and is often ignored
The presence or absence of leukocytes must be confirmed microscopically
Nitrates in urine
A positive on this test is significant as you do not get false +
In LA, a + result may indicate that the animal has a UTI
In SA it is generally only found in rabbits
urinalysis analyzers
In clinic machines are generally semi automated
Htere are machines that will read tha urine stips
Separate machines are now also available that will perform a sediment exam on the urine
Reference labs may have automated machines that perform the chemical, physical, and sediment analysis
