Urinalysis Flashcards
What are 4 factors that may account for interpretation of urine components to vary?
- Sample type
- Urine concentration (SG)
- Urine pH
- Type of sediment present
What does it mean that SG is a sliding scale approach?
As SG increases –> increased concentrations of solutes (normal excreted amount in smaller volume)
Increase concentration can cause increase in some test results even though total solutes being excreted is normal.
Name three major methods of urine collection. How can the method of collection influence your interpretation?
- Cystocentesis – localized and easy to figure out where things come from.
- Catheterization – same as cysto
- Free catch – we will interpret RBC, protein, etc differently. Less localization of a problem.
What are the components of a physical examination of urinalysis?
- Color
- Turbidity
- Specific gravity
- Odor
- Volume
Interpret these color changes in the urine:
- Red to brownish
- Yellow- brown
- Brownish
- yellow to yellow-amber
- Blood (Hb) or Myoglobin (oxidized Hb)
- Bilirubin
- Methemoglobin
When are there exceptions to normal, clear urine turbidity?
Horses – cloudy due to mucus/crystals (calcium carbonate)
Rabbits – may look pyuric (carbonate and oxalate crystals)
What function of the kidney does SG measure?
Tubular function
T/F
Increased USG always indicates inadequate tubular function
False
Abnormally high amounts of some urinary components can directly increase it independent of tubular concentrating fxn
T/F
Ammonia is odorless
False
Ammonium is odorless
What is included on a urine chemical strip?
Urine protein
Ketones
Glucose
Bilirubin
Urobilinogen
Blood ("occult" blood)
pH
Nitrite
LeukocytesWhat ways can we test for urine protein?
- Chemistry strip
- Acid precipitation test (Sulfosalicylic acid – SSA)
- Urine Protein:Creatinine Ratio (UPC)
What protein does the chemistry test strip predominantly look at (specificity)?
Albumin
What can cause a mild false positive protein test strip?
Alkaline pH >8
What is the benefit of using a SSA urine protein test instead of the chemistry strip? When would we use this?
Looks at both albumin and globulin
Less sensitive to pH changes
Do this test with any sample pH > 7
To confirm presence of non-albumin proteins (e.g. myeloma light chains)
What is a normal UPC result in dogs and cats?
Dogs </= 0.4
How would you interpret these UPC findings? < 1.0 > 1.0 > 3.0 > 10
< 1.0 gray area (repeat, monitor)
> 1.0 definite increased protein loss (probably glomerular but tubular is possible)
> 3.0 glomerular (tubular is very unlikely)
> 10 Glomerulonephritis or Amyloidosis
When would you decide to complete a UPC?
Unexplained proteinuria
- Confirm that the degree of proteinuria is clinically significant
- provides a baseline value for monitoring progression of dz or response to therapy
Why repeat a U/A?
confirm persistence and magnitude of unclear causes b/f performing further diagnostics
follow progression of obvious sources of proteinuria (hemorrhage, inflammation)
What are 6-7 major causes of proteinuria?
- Hemorrhage
- Inflammation
- Pre-renal “physiologic”
- Pre-renal “overflow”
- Primary Glomerular renal dz
- Primary Tubular renal dz
- Strenuous exercise
What are the three ketone bodies?
- Acetone
- Acetoacetate
- B hydroxybutyrate
What ketone do test strips look for?
Acetoacetate
What ketone is the primary one produced clinically?
Beta hydroxybutyrate
What may cause a false negative ketone test?
Test strips only test for Acetoacetate.
The strip may not be looking for the primary ketone causing the problem (beta hydroxybutyrate or acetone)
What are three clinical conditions associated with ketonuria?
Diabetes mellitis
Lactation
Pregnancy with twins (common in cattle)
What is the significance of ketonuria?
Tells us the animal has a negative energy balance
What comes first, ketonuria or ketonemia?
Ketonuria
What will we see on our acid/base profile with ketoacidosis?
Increased anion gap
Decreased TCO2
What are some associated laboratory changes with ketone production?
Hyperglycemia (DM)
Hypoglycemia (lactation)
Glucosuria
Increased AG, decrease TCO2
What are two major mechanisms for glucosuria?
- Overflow
Seen in DM when the glucose filtered through the glomerulus exceeds renal threshold - Damaged PCT
Glucose is unable to be reabsorbed by the renal tubules
What is the renal threshold for cows, horses, dogs, cats, and other?
Cow (100)
Horse (150)
Dog and other (180)
Cat (280)
When interpreting results, what are three considerations you should make through your thought process?
- Sample consideration (age, storage)
- Assay consideration ( pH, protein, bilirubin, RBC)
- Physiologic considerations (Entry, production, and why it’s there – protein, bilirubin, ketones…)
Which is true in a normal animal?
A. urine creatinine > urine proteins
B. urine creatinine < urine proteins
A
When may we see a false negative urine glucose result?
They occur with high urinary concentrations of ascorbic acid (vitamin C) – Dogs and cats synthesize their own
T/F
Urine glucose measurements are a useful way to monitor insulin therapy
False
What are some laboratory changes associated with glucosuria?
Serum glucose
Ketonuria
Proteinuria (PCT damage)
What can lead to a false negative bilirubin?
Exposure to light
neutralizes bilirubin –> biliverdin
What test can we use that is more sensitive for bilirubin than the chemistry strip?
Ictotest (tablet test)
What should your interpretation be of bilirubinuria?
Cholestasis
What is special about dogs and bilirubin in the urine?
Dogs tubules can convert heme into Bc and pass it it urine
What is the difference b/w dogs and cats when interpreting urine bilirubin?
Dogs – small amount of bilirubin in urine can be normal
renal threshold < serum Bc cutoff : normal serum bilirubin can exceed a dog’s renal threshold.
Cats – Any bilirubin in urine is abnormal.
renal threshold > serum Bc cutoff
The test strip is sensitive to what 3 things when detecting occult blood?
- Intact RBC
- Free Hemoglobin
- Myoglobin
What has to happen for intact RBC, free Hb, and myoglobin to be present?
Intact RBCs – Hemorrhage
Free Hemoglobin – Hemolysis
Myoglobin – Muscle damage
What do you call RBC in the urine vs. Hemoglobin in the urine? You will know the difference based on the physiologic insult
RBC - hematuria
Hemoglobin - hemaglobinuria
How can you tell if it’s intact RBC, hemoglobin or myoglobin in the urine?
RBC – supernatent (clear after spinning); RBC observed on sediment
Hemoglobin – serum is red
Myoglobin – serum is clear (rapidly cleared from plasma)
When is it incorrect to say hemoglobinuria when there is hemoglobin in the urine? Explain
If it is occurs after urinary tract hemorrhage
- storage time: old sample
- pH: alkaline damages organic material
- SG: dilute
How do you confirm the Hb in the urine is actually from IV hemolysis and not from sample alterations?
Look at the Hct and RBC morph for characterization of hemolytic anemia
Why can’t myoglobin be present in the serum?
No serum binding proteins
Fully excreted by the urine
What factors can affect urine pH?
Storage time – CO2 loss –> alkalization –> cells and casts breakdown and become underestimated
Bacteria – urease (urea –> ammonia –> increase pH)
When will you see ghost cells on urinalysis?
Hemolysis after urinary tract hemorrhage
What is paradoxical aciduria? What will happen to urine pH?
Acidic urine pH with metabolic alkalosis
Metabolic alkalosis –> hypokalemia causes Na/K pump in kidney to switch to Na/H pump to preserve K in blood –> increased H pumped into urine –> acidic urine
What is renal tubular acidosis? What will happen to urine pH?
Alkaline urine pH with hyperchloremic metabolic acidosis
alteration in tubular function –> Chloride is pumped into the blood while HCO3 is pumped into urine –> alkaline urine
What is the urine pH for carnivores vs. herbivores?
Carnivores – aciduria (5.5-7.0)
Herbivores – alkaline urine (7.0-8.4)
Explain post-prandial “alkaline tide”
1-3 hours after animal is fed, urine will become alkaline due to HCl excretion from stomach causes HCO3 production
When is there nitrite in urine?
Bacterial detection
Bacterial reductase: nitrate –> nitrite
What are special considerations when looking at nitrite?
Urine needs to be in the bladder for at least 4 hours so there is enough reductase present
Poor sensitivity (don’t trust a negative results)
What does the leukocyte strip look at? How do you confirm?
Senses leukocyte esterase activity
Confirm with sediment
What can happen if you refrigerate urine?
Refrigeration can preserve chemical and sediment components BUT calcium oxylate dihydrate crystals can form… may be present in normal animals also (not too concerning)
What may happen with urine at room temperature?
Cells, chemicals, and casts may breakdown from alkalinization
What are reference intervals for urine dipstick for protein, bilirubin, ketones, occult blood, glucose? RBC, WBC, Epithelial cells, bacteria, casts?
Protein </=1+ cat negative/0
Occult blood: negative
What are reference intervals/normal for urine sediment for RBC, WBC, epithelial cells, bacteria, casts?
RBC 0-5 WBC 0-3 Epithelial cells Occasional Bacteria None Casts None
What conditions does the sediment look for?
Hemorrhage
Inflammation
Neoplasia
Hyperplasia/dysplasia
T/F
Cells, casts, and crystals are less stable in concentrate urine
False
less stable in unconcentrated/dilute urine
Where do casts form?
Distal tubules and ascending loop of Henle
