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