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Clinical Pathology > Urinalysis > Flashcards

Urinalysis Flashcards

1
Q

What is the best sample for Urinalysis?

A
  • Sterile (cystocentesis) if for culture & sensitivity
  • Best results - analyze within 30 min
  • Delayed - refrigerate & protect from light
    • warm to room temp for analysis
    • consistent volume
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2
Q

What do the different urine colors indicate?

A
  • Colorless - dilute
  • Light yellow - normal
  • Dark yellow - normal or concentrated (urochromes, flavins)
  • Red - hemoglobinuria, myoglobinuria, hematuria
  • Orange/brown - bilirubin
  • Coffee-brown - Myoglobinuria, Methemoglobinuria
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3
Q

What are the different transparencies of urine indicative of?

A
  • Clear: healthy (most animals)
  • Hazy to Cloudy: crystals, cells, mucus, bacteria, casts, spermatozoa, or other material
    • Horses normally have cloudy urine
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4
Q

Why is horse urine normally cloudy?

A

mucoproteins in urine produced by renal epithelial cells

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5
Q

What does the Urine dip-stick reliably test for?

A
  • Protein
  • Glucose
  • Ketones
  • pH
  • Bilirubin
  • Hemoprotein (blood)
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6
Q

What is the Urine Dip-stick test unreliable for?

A
  • Urobilinogen - product of bacterial degradation of bilirubin in the gut
  • Nitrite - screen for bacteruria in humans, not animals
  • Leukocyte esterase - polyuria in people, not animals
  • Specific gravity
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7
Q

What determines Urine pH?

A
  • In Health - primarily by diet
    • increased protein catabolism = more acidic urine
      • 6 - 7.5 in dogs/cats
    • decreased protein catabolism = more alkaline urine
      • 7.5-8.5 in equids/ruminants
  • Changes occur in response to systemic A/B disorders
    • but urine pH is NOT an accurate indicator of A/B balance
  • Infection with urease-producing bacteria results in alkalinization of the urine
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8
Q

What Urine protein does the Dip-stick test for?

A
  • Measures albumin best
  • Also sensitive to hemoglobin & myoglobin
  • Does NOT detect Bence-Jones proteins
  • Very alkaline urine OR contamination by some cleaning agents will cause a false positive
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9
Q

What rule outs have to be done before attributing proteinuria to renal disease?

A
  • Prerenal (overload) proteinuria
    • hemoglobinuria
    • myoglobinuria
  • Postrenal proteinuria
    • hemorrhage into the genitourinary tract
    • inflammation, trauma, neoplasia
      *
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10
Q

Should there be glucose in urine?

A
  • Glucose is freely filtered in the glomerulus - no barrier to entry of glucose into the tubular filtrate
  • Glucose is efficiently reabsorbed in the proximal tubule
    • NO glucose should be in urine
    • Glucosuria is present if the renal threshold is exceeded
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11
Q

What are the different renal thresholds for glucose in different species?

A
  • Dogs - 180mg/dL
  • Cats - 280
  • Horse - 160
  • Cattle - 100
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12
Q

How are false positives/negatives for urine glucose acheived?

A
  • False positive - contamination with cleaning agents
  • False decreases/negative:
    • Vit C
    • Presence of ketones
    • Sensitivity of test decreased with cold urine
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13
Q

What is Hyperglycemic glucosuria?

A
  • Most common cause of glucosuria
  • Hyperglycemia caused by:
    • Diabetes mellitus - lack of insulin
    • Severe pancreatitis
    • Hyperadrenocorticism - insulin resistance due to increased cortisol secretion
    • Severe stress/excitement - insulin resistance due to catecholamine release
    • Iatrogenic - admin of glucose containing fluids
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14
Q

What are other interpretations of Glucosuria?

A
  • Hyperglycemic glucosuria
  • Normoglycemic glucosuria
    • previous, transient episode of hyperglycemia
  • Renal tubular defect
    • Acquired - damage to tubular epithelium
      • eg - gentamycin tox
    • Inherited - Canine Fanconi-like syndrome
      • Basenji & labs
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15
Q

What Ketones is the Urine Dip-stick testing ro?

A
  • Acetone, Acetoacetate & B-hydroxybutyrate are the ketones
    • test only detects acetone & acetoacetate
    • B-hydroxybutyrate is produced in the largest quantity though
  • Ketones are NOT present in healthy urine
  • False positives can occur with pigmented urine
  • Ketonuria indicates a systemic problem - precedes detectable ketonemia
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16
Q

What causes ketone bodies?

A
  • Produced when there is a negative energy balance
    • Starvation or inability to utilize carbohydrates (lake of insulin)
      • Dogs/cats: diabetes mellitus
      • Ruminants: metabolic disorders associated with lactation, late gestation
17
Q

How sensitive is the Urine Dip-stick to blood?

A
  • Very sensitive - positive with only 5-20 RBCs/uL
  • Positives seen with:
    • Hematuria - RBCs in urine
    • Hemoglobinuria - free hemoglobin in urine
    • Myoglobinuria - free myoglobin in urine
18
Q

How can one differentiate between Hematuria, hemoglobinuria, and myoglobinuria?

A
  • Hematuria
    • supernatant is not, or is only barely red
    • RBCs in sediment
    • Normal plasma color (clear)
  • Hemoglobinuria
    • Occurs due to intravascular hemolysis
    • Red, clear supernatant
    • Few or no RBCs in sediment
    • Red plasma (hemoglobinemia)
    • Evidence of anemia (hemolytic) on CBC
  • Myoglobinuria
    • Occurs due to muscle injury & necrosis
    • Red-brown supernatant
    • Few or no RBCs in sediment
    • Plasma normal color (clear)
    • increased CK and ASt
19
Q

What does the urine dipstick test for bilirubin tell a clinician?

A
  • Bilirubin - produced from heme degradation (hemolytic disease or hepatobiliary disorders)
  • Positive - conjugated bilirubin in urine
    • Bilirubinuria may precede hyperbilirubinemia
  • +1 reaction in concentrated urine is common in dogs
  • Bilirubinuria in cats, horses and cattle is significant
  • False decrease:
    • bilirubin degrades with exposure to UV light
20
Q

What is the normal amount of RBCs and WBCs in urine sediment?

A
  • RBCs < 5RBC/hpf (40x)
  • WBCs <5WBC/hpf
    • pyuria indicates inflammation
21
Q

What can all be found in urine sediment?

A
  • RBCs
  • WBCs
  • Epithelial cells
  • Bacteria
  • fat
  • crystals
22
Q

When is bacteria in urine sediment significant?

A
  • Voided and catheterized samples may have some contaminant bacteria
  • Cystocentesis samples should have NONE
  • Bacteriuria representing and infection is usually accompanied by pyuria
23
Q

What does Crystalluria indicate?

A

Urine is supersaturated with compounds that comprise the crystals

may be seen in health or disease

24
Q

What are Struvite Crystals?

A
  • Magnesium ammonium phosphate or tripple phosphate cyrstals
  • Colorless
  • 3-D prism-like (coffin lids)
  • Often in urine of healthy animals
  • Prefer neutral to alkaline urine - can form in any pH
  • Bacterial cystitis predisposes to struvite crystaluria and urolithiasis
25
Q

What are Calcium Oxalate Dihydrate Crytals?

A
  • Colorless squares with corners connected by a central ‘X’
  • Can develop in any pH
  • See often in healthy animals
  • Can develop in stored urine
  • With or without calcium oxalate urolithiasis
    • secondary to abnormal calcium excretion
26
Q

What are Bilirubin Crystals?

A
  • May be associated with bilirubinuria & bilirubinemia
  • Fine needle-like crystalline structure
  • Dogs:
    • Fairly common in highly concentrated urine
    • Often not clinically significant
  • Cats, horses & cattle
    • Pathologically significant
      • Disorders that cause bilirubinuria
27
Q

What are Calcium Carbonate crystals?

A
  • 2 forms:
    • Large yellow-brown or colorless spheroids with radial striations
    • Smaller round, ovoid to dumbbell-shaped
  • Common in urine of normal horses, rabbits, guinea pigs, & goats
  • In dogs and cats with renal disease:
    • need to rule or melamine-cyanuric acid crystals
28
Q

What are Urate Cystals?

A
  • Uric Acid & ammonium urate/biurate
  • Predisposed with Portosystemic shunts
    • with or without urate uroliths
  • Other hepatic disease where hyperammonemia exists
  • Dalmatians & English bulldogs prone
    • decreased degradation of uric acid to allantoin via uricase
29
Q

What are Calcium Oxalate Monohydrate Crystals?

A
  • Indicate supersaturation with calcium and oxalate
  • Hemp-seed, or dumbbell shaped
    • Can be seen in a low # in health
  • Flat, six-sided form (fence pickets)
    • Ethylene glycol poisoning - not always seen
    • May also be seen with other causes of hypercalciuria
30
Q

What are some of the less common crystals that can be found in urine sediment?

A
  • Cystine Crystals
    • Flat, colorless, hexagonal
    • often aggregate in layers
    • form in acidic urine
    • Inherited sex-linked metabolic abnormality resulting in tubular inability to reabsorb cystine and occasionally other AA
      • avoid breeding affected animals
  • Drug Associated Crystals
    • Sulfas, ampicillin, radiopaque contast agents
31
Q

What are Casts?

A
  • Form in the distal tubules and collecting ducts
  • Cylindrical molds - composed mainly of Tamm-Horsefull mucoprotein
  • Named according to composition
  • Cellular, granular & waxy casts represent different stages of cell degeneration
  • How casts appear depends upon the length of time it was in the tubules prior to being shed
32
Q

What are Casts?

A
  • Form in the distal tubules and collecting ducts
  • Cylindrical molds - composed mainly of Tamm-Horsefull mucoprotein
  • Named according to composition
  • Cellular, granular & waxy casts represent different stages of cell degeneration
  • How casts appear depends upon the length of time it was in the tubules prior to being shed
33
Q

What are Hyaline Casts?

A
  • Form in the absence of cells in the tubular lumen
  • Protein only
  • Rounded ends and parallel sides are diagnostic features
    • often cigar-shaped
  • Few (<2/lpg) may be seen in urine of healthy animals
  • High #s associated with proteinuria - not always seen
    • especially glomerular proteinuria
34
Q

What are epithelial cell casts?

A
  • Desquamation of epithelium form renal tubules
  • Cast is shed shortly after being formed
  • Cells appear intact and indicate renal disease
  • Result form
    • Ischemia
    • infarction
    • nephrotoxicity (aminoglycosides, amphotericin B)
  • Earliest indicator of renal tubular cell injury when drugs potentially damaging to kidney are used
  • NOT seen normally
35
Q

What are Granular Casts?

A
  • Degenerated cellular casts (epithelial, WBC, RBC)
  • Low numbers in health after exercise associated with protein metabolism
  • Large #s may indicate tubular degeneration consistent with:
    • nephritis
    • nephrotoxin
    • infection
    • protein losing nephropathy
36
Q

What are Waxy Casts

A
  • Long standing franular casts
  • Have sharp squared-off ends
  • Smooth consistency, but more refractile than hyaline casts
  • Generally indicate chronic tubular lesions
  • often associated with severe renal disease
    • glomerulonephritis
    • amyloidosis
  • NOT seen normally
  • ALWAYS PATHOLOGIC
37
Q

What are Waxy Casts

A
  • Long standing franular casts
  • Have sharp squared-off ends
  • Smooth consistency, but more refractile than hyaline casts
  • Generally indicate chronic tubular lesions
  • often associated with severe renal disease
    • glomerulonephritis
    • amyloidosis
  • NOT seen normally
  • ALWAYS PATHOLOGIC
38
Q

Do casts correlate with the severity of disease?

A
  • NO
  • Large #s
    • always indicate active generalized renal disease
      • usually acute, but may be reversible or irreversible
  • Casts are intermittently shed
    • lack of casts does NOT rule out renal disease

Clinical Pathology (12 decks)

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