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Clinical Chemistry (me) > Urinalysis > Flashcards

Urinalysis Flashcards

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1
Q

What are 4 factors that may account for interpretation of urine components to vary?

A
  1. Sample type
  2. Urine concentration (SG)
  3. Urine pH
  4. Type of sediment present
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2
Q

What does it mean that SG is a sliding scale approach?

A

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.

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3
Q

Name three major methods of urine collection. How can the method of collection influence your interpretation?

A
  1. Cystocentesis – localized and easy to figure out where things come from.
  2. Catheterization – same as cysto
  3. Free catch – we will interpret RBC, protein, etc differently. Less localization of a problem.
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4
Q

What are the components of a physical examination of urinalysis?

A
  1. Color
  2. Turbidity
  3. Specific gravity
  4. Odor
  5. Volume
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5
Q

Interpret these color changes in the urine:

  1. Red to brownish
  2. Yellow- brown
  3. Brownish
  4. yellow to yellow-amber
A
  1. Blood (Hb) or Myoglobin (oxidized Hb)
  2. Bilirubin
  3. Methemoglobin
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6
Q

When are there exceptions to normal, clear urine turbidity?

A

Horses – cloudy due to mucus/crystals (calcium carbonate)

Rabbits – may look pyuric (carbonate and oxalate crystals)

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7
Q

What function of the kidney does SG measure?

A

Tubular function

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8
Q

T/F

Increased USG always indicates inadequate tubular function

A

False

Abnormally high amounts of some urinary components can directly increase it independent of tubular concentrating fxn

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9
Q

T/F

Ammonia is odorless

A

False

Ammonium is odorless

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10
Q

What is included on a urine chemical strip?

A 
Urine protein
Ketones
Glucose
Bilirubin
Urobilinogen
Blood ("occult" blood)
pH
Nitrite
Leukocytes
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11
Q

What ways can we test for urine protein?

A
  1. Chemistry strip
  2. Acid precipitation test (Sulfosalicylic acid – SSA)
  3. Urine Protein:Creatinine Ratio (UPC)
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12
Q

What protein does the chemistry test strip predominantly look at (specificity)?

A

Albumin

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13
Q

What can cause a mild false positive protein test strip?

A

Alkaline pH >8

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14
Q

What is the benefit of using a SSA urine protein test instead of the chemistry strip? When would we use this?

A

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)

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15
Q

What is a normal UPC result in dogs and cats?

A

Dogs </= 0.4

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16
Q 
How would you interpret these UPC findings?
< 1.0 
> 1.0
> 3.0
> 10
A

< 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

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17
Q

When would you decide to complete a UPC?

A

Unexplained proteinuria

  1. Confirm that the degree of proteinuria is clinically significant
  2. provides a baseline value for monitoring progression of dz or response to therapy
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18
Q

Why repeat a U/A?

A

confirm persistence and magnitude of unclear causes b/f performing further diagnostics

follow progression of obvious sources of proteinuria (hemorrhage, inflammation)

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19
Q

What are 6-7 major causes of proteinuria?

A
  1. Hemorrhage
  2. Inflammation
  3. Pre-renal “physiologic”
  4. Pre-renal “overflow”
  5. Primary Glomerular renal dz
  6. Primary Tubular renal dz
  7. Strenuous exercise
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20
Q

What are the three ketone bodies?

A
  1. Acetone
  2. Acetoacetate
  3. B hydroxybutyrate
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21
Q

What ketone do test strips look for?

A

Acetoacetate

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22
Q

What ketone is the primary one produced clinically?

A

Beta hydroxybutyrate

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23
Q

What may cause a false negative ketone test?

A

Test strips only test for Acetoacetate.

The strip may not be looking for the primary ketone causing the problem (beta hydroxybutyrate or acetone)

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24
Q

What are three clinical conditions associated with ketonuria?

A

Diabetes mellitis
Lactation
Pregnancy with twins (common in cattle)

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25
Q

What is the significance of ketonuria?

A

Tells us the animal has a negative energy balance

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26
Q

What comes first, ketonuria or ketonemia?

A

Ketonuria

27
Q

What will we see on our acid/base profile with ketoacidosis?

A

Increased anion gap

Decreased TCO2

28
Q

What are some associated laboratory changes with ketone production?

A

Hyperglycemia (DM)
Hypoglycemia (lactation)
Glucosuria
Increased AG, decrease TCO2

29
Q

What are two major mechanisms for glucosuria?

A
  1. Overflow
    Seen in DM when the glucose filtered through the glomerulus exceeds renal threshold
  2. Damaged PCT
    Glucose is unable to be reabsorbed by the renal tubules
30
Q

What is the renal threshold for cows, horses, dogs, cats, and other?

A

Cow (100)
Horse (150)
Dog and other (180)
Cat (280)

31
Q

When interpreting results, what are three considerations you should make through your thought process?

A
  1. Sample consideration (age, storage)
  2. Assay consideration ( pH, protein, bilirubin, RBC)
  3. Physiologic considerations (Entry, production, and why it’s there – protein, bilirubin, ketones…)
32
Q

Which is true in a normal animal?
A. urine creatinine > urine proteins
B. urine creatinine < urine proteins

A

A

33
Q

When may we see a false negative urine glucose result?

A

They occur with high urinary concentrations of ascorbic acid (vitamin C) – Dogs and cats synthesize their own

34
Q

T/F

Urine glucose measurements are a useful way to monitor insulin therapy

A

False

35
Q

What are some laboratory changes associated with glucosuria?

A

Serum glucose
Ketonuria
Proteinuria (PCT damage)

36
Q

What can lead to a false negative bilirubin?

A

Exposure to light

neutralizes bilirubin –> biliverdin

37
Q

What test can we use that is more sensitive for bilirubin than the chemistry strip?

A

Ictotest (tablet test)

38
Q

What should your interpretation be of bilirubinuria?

A

Cholestasis

39
Q

What is special about dogs and bilirubin in the urine?

A

Dogs tubules can convert heme into Bc and pass it it urine

40
Q

What is the difference b/w dogs and cats when interpreting urine bilirubin?

A

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

41
Q

The test strip is sensitive to what 3 things when detecting occult blood?

A
  1. Intact RBC
  2. Free Hemoglobin
  3. Myoglobin
42
Q

What has to happen for intact RBC, free Hb, and myoglobin to be present?

A

Intact RBCs – Hemorrhage
Free Hemoglobin – Hemolysis
Myoglobin – Muscle damage

43
Q

What do you call RBC in the urine vs. Hemoglobin in the urine? You will know the difference based on the physiologic insult

A

RBC - hematuria

Hemoglobin - hemaglobinuria

44
Q

How can you tell if it’s intact RBC, hemoglobin or myoglobin in the urine?

A

RBC – supernatent (clear after spinning); RBC observed on sediment
Hemoglobin – serum is red
Myoglobin – serum is clear (rapidly cleared from plasma)

45
Q

When is it incorrect to say hemoglobinuria when there is hemoglobin in the urine? Explain

A

If it is occurs after urinary tract hemorrhage

  • storage time: old sample
  • pH: alkaline damages organic material
  • SG: dilute
46
Q

How do you confirm the Hb in the urine is actually from IV hemolysis and not from sample alterations?

A

Look at the Hct and RBC morph for characterization of hemolytic anemia

47
Q

Why can’t myoglobin be present in the serum?

A

No serum binding proteins

Fully excreted by the urine

48
Q

What factors can affect urine pH?

A

Storage time – CO2 loss –> alkalization –> cells and casts breakdown and become underestimated

Bacteria – urease (urea –> ammonia –> increase pH)

49
Q

When will you see ghost cells on urinalysis?

A

Hemolysis after urinary tract hemorrhage

50
Q

What is paradoxical aciduria? What will happen to urine pH?

A

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

51
Q

What is renal tubular acidosis? What will happen to urine pH?

A

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

52
Q

What is the urine pH for carnivores vs. herbivores?

A

Carnivores – aciduria (5.5-7.0)

Herbivores – alkaline urine (7.0-8.4)

53
Q

Explain post-prandial “alkaline tide”

A

1-3 hours after animal is fed, urine will become alkaline due to HCl excretion from stomach causes HCO3 production

54
Q

When is there nitrite in urine?

A

Bacterial detection

Bacterial reductase: nitrate –> nitrite

55
Q

What are special considerations when looking at nitrite?

A

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)

56
Q

What does the leukocyte strip look at? How do you confirm?

A

Senses leukocyte esterase activity

Confirm with sediment

57
Q

What can happen if you refrigerate urine?

A

Refrigeration can preserve chemical and sediment components BUT calcium oxylate dihydrate crystals can form… may be present in normal animals also (not too concerning)

58
Q

What may happen with urine at room temperature?

A

Cells, chemicals, and casts may breakdown from alkalinization

59
Q

What are reference intervals for urine dipstick for protein, bilirubin, ketones, occult blood, glucose? RBC, WBC, Epithelial cells, bacteria, casts?

A

Protein </=1+ cat negative/0

Occult blood: negative

60
Q

What are reference intervals/normal for urine sediment for RBC, WBC, epithelial cells, bacteria, casts?

A 
RBC 0-5
WBC 0-3
Epithelial cells Occasional
Bacteria None
Casts None
61
Q

What conditions does the sediment look for?

A

Hemorrhage
Inflammation
Neoplasia
Hyperplasia/dysplasia

62
Q

T/F

Cells, casts, and crystals are less stable in concentrate urine

A

False

less stable in unconcentrated/dilute urine

63
Q

Where do casts form?

A

Distal tubules and ascending loop of Henle

Clinical Chemistry (me) (4 decks)

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