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
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
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
4
Q
Why is horse urine normally cloudy?
A
mucoproteins in urine produced by renal epithelial cells
5
Q
What does the Urine dip-stick reliably test for?
A
- Protein
- Glucose
- Ketones
- pH
- Bilirubin
- Hemoprotein (blood)
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
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
- increased protein catabolism = more acidic urine
- 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
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
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
*
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
11
Q
What are the different renal thresholds for glucose in different species?
A
- Dogs - 180mg/dL
- Cats - 280
- Horse - 160
- Cattle - 100
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
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
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
- Acquired - damage to tubular epithelium
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
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
- Starvation or inability to utilize carbohydrates (lake of insulin)
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
- Pathologically significant
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
- always indicate active generalized renal disease
- Casts are intermittently shed
- lack of casts does NOT rule out renal disease
