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Nephron
Functional unit of the kidney - filtration and reapsorbtion
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3 steps of urine formation
- 1. Filtration
- 2. Reapsorbtion
- 3. Storage
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Degree of kidney filtration depends on
- Pt's blood pressure
- Amount of blood reaching glomerulus
- Laws of diffusion
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Freely filtered substances in the kidney include
- H20
- Electrolytes
- Glucose
- Amino acids
- BUN & Creatinine
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BUN & Creatinine
Non-protein nitrogenous waste products
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Urea comes from
Protein breakdown --> ammonia -(liver)-> urea --> urine
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Creatinine comes from
Muscle contraction --> creatinine --> urine
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Hormones that act on renal tubules
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ADH
- Released from pituitary
- Tells renal tubules to reabsorb H20
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Aldosterone
- Released from adrenals
- Controls sodium reabsorption and pottasium excretion
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Normal glucose for dogs
100mg/dl
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renal threshold for glucose
160-180mg/dl
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Glucosuria
If blood glucose is ABOVE renal threshold, filtered glucose will not get reapsorbed and glucose will be present in the urine
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Early AM urine collection advantages
- Decreased H2O intake
- Most likely to show urine concentration
- Normal color is yellow
- Renal failure, can't concentrate urine
- Increased chance of observing abnormalities like crystals
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Early AM urine collection disadvantages
Poor cytology because urine is "old", "old" cells
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4 methods of collecting urine sample
- Voided
- Manual
- Catheterization
- Cystocentesis
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Voided (free catch) urine collection
- Easiest on animal, clients can do, no iatrogentic trauma
- Not best method for culture because of bact. contamination.
- Mid-stream catch decreases contamination, collect into a clean container
- cats = empty litter pan with beads
- female dogs = pie pans
- horses = stimulate urination by rubbing warm wet cloth on lower abdomen
- cattle = stimulate urination by tickling vulva
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Manual expression urine collection
- Can get bladder out of the way when pt is under anesthesia for abdominal surgery
- may require anesthesia, big dogs with tense muscles are hard
- May cause iatrogenic trauma and cause increased RBCs.
- Could rupture the bladder.
- Large animal = through rectum
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Catherterization
- Can usually get sample right away
- Can clear obstruction
- Can monitor urinary output with a foley
- Ok for culture
- May require anesthesia, may produce trauma
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Cystocentesis
- Can usually get sample right away
- Does not require anesthesia, animals usually handle better then catheterization
- Causes iatrogenic trauma --> RBCs
- 22g needle about 1"-1.5" long, 6cc or 12cc syringe, can do in dorsal but also lateral or standing
- Draw as much bladder as possible so hole shrinks, Do NOT redirect to avoid colon contamination
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Urine is good for ___________ at room temp
30 mins
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Urine is good for ________ refrigerated
6 hours
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When urine is left at room temp, over time...
- Increased bact
- Increased crystals
- Urine gets cloudy
- Cells disintegrate
- Casts break down
- pH changes (tends to increase)
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Chemically preserving urine
- 1 gtt 40% formaldehyde to 1 oz. urine
- If used, do chemistries first (dip stick)
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4 parts of a routine U/A
- 1. Macroscopic eval
- 2. USG
- 3. Urine chemistries
- 4. Microscopic eval
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Urinalysis
Determines the function of kidneys and other organs
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Macroscopic eval
- Note color and concentration.
- Normal = straw - amber
- Dark yellow = increased concentration because of decreased H2O
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Hematuria
- RBCS in urine. Red to reddish-brown and cloudy.
- Inflammation
- Trauma
- Urolithiasis
- Neoplasia
- Coagulopathy
- Rough cysto/catheter/manual
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Hemoglobinuria
- HgB in urine
- Red/reddish-brown and transparent
- Usually with hemolytic plasma
- AIHA
- Incompatible blood transfusion
- toxins/poisons/snake venom
- RBC parasites
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Myoglobinuria
- Myoglobin in urine
- Red/reddish-brown
- clear plasma
- Muscle cell lysis:
- Exertional rhabdomyolysis
- Extreme muscle exertion
- Crushing injuries
- Heat stroke
- Electric shock
- Snake bites
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Bilirubinuria
- Bilirubin in urine
- Dark yellow/yellowish-orange/yellow brown
- Stains fingers
- Excessive hemolysis
- HBO
- Lover disease
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Normal canine/feline urine coloration
Clear/transparent. Increased concentration = hazy
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Normal equine urine coloration
Cloudy due to crystals and mucus
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Normal ruminant urine coloration
- Clear if fresh
- Cloudy after standing
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Normal lab animal urine
Cloudy, almost milky, due to crystals
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Strong ammonia smelling urine may indicate _______________
Cystitis due to urease + bacteria
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Sweet and fruity smelling urine may indicate ______________
Pseudomonas or ketones (due to DM)
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Foam in urine may indicate _____________
Protein
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USG
- Urine Specific Gravity
- Evaluates renal-tubule function
- (Response to ADH and reabsorption of H2O)
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USG range to worry about
1.008-1.012 (1.015 in the cat)
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Isosthinuric urine
Same USG as glomerular filtration
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Fixed USG
- range of 1.008-1.012 (1.015 in cats) that does change regardless of hydration status
- 1/3-3/4 nephrons are non functional
- Renal failure
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Reasons for decreased USG
- Pale/Dilute Urine
- Increased Fluid/Decreased "Stuff":
- Pyometra
- DI
- Cushings
- Diuresis
- IV fluids
- renal failure
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Reasons for increased USG
- Increased concentration (dark yellow)
- Dehydration
- Acute renal failure/shut down
- Shock
- DM
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Carnivorous Urine pH
Acidic
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Herbivorous Urine pH
Alkaline
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Omnivorous Urine pH
Dependent on diet
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Acidic urine causes
- high protein diets
- nursing young
- Protein catabolic states (high fever/starvation)
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Alkaline urine causes
- Vegetable based diets
- UTI caused by Urease + organism
- Urine retention
- Urine allowed to stand open to air at room temperature
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Normal animal should have ______________ protein in their urine
- 0-trace amounts of protein when sample is a cysto
- Slightly higher amounts from voided sample
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Proteinuria
Usually indicates urinary tract and kidney disease
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Normal animals should have __________ glucose in their urine
NO
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Glucosuria causes
- Blood glucose exceeds the renal threshold
- 160-180 mg/dl dogs
- 280-300 mg/dl cats
- DM
- Stress/fear/excitement
- High carbohydrate meal
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Normal animals should have _________ ketones in their urine
NO
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Ketonuria causes
- DM
- Prolonged anorexia/starvation
- ketosis in lactating and pregant cows and ewes (pregnancy toxemia)
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Centrifuge urine at ___________ rpm for _________ min
1200-1500 rpm for 3-5 minutes
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Sedi-stain
Used on urine sample to show nuclear detail on microscopic eval
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3 types of epithelial cells
- 1. Squamous Epithelial Cells
- 2. Transitional Epithelial Cells
- 3. Renal Tubular Epithelial Cells
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Squamous Epithelial Cells
- found in distal 1/3 of erethrea, vagina, vulva, and prepuse.
- Largest epithelial cell
- Nucleas is size of an RBC
- Normal in MILD amounts
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Transitional Epithelial Cells
- Line bladder, ureters, renal peelvis, and proximal part of the urethra
- Vary in size and shape
- Round, pear shaped, caudate
- Large nucleas
- Granular appearance
- normal in MILD amounts
- Seen more with cysto
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Increased Transitional Epithelial Cells can indicate ___________________
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Inflammation
- Urolithiasis
- Neoplasia
- Trauma
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Renal Tubular Epithelial Cells
- Originate in the Renal Tubules
- Hard to ID
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Triple Phosphate Crystals
- Struvites
- Alkaline urine
- Normal in mild amounts
- Increased amounts can indicate Urolethiasis
- Coffin lids
- Coloreless
- Tx = acidify urine with diet
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Calcium Oxalate Crystals
- Acidic urine
- Normal in MILD amounts in dogs, cats, and occ. horses
- Can indicate urolethiasis or ethylene glycol toxicity
- Tx = make urine alkaline with diet
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Hippuric Acid Crystal
- Form of Calcium Oxalate Monohydrate
- Always pathological
- Indicate Ethylene Glycol toxicity
- Look like picket-fence posts
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Calcium Carbonate Crystals
- Common in horses
- Reason urine is cloudy when combined with mucus
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Bilirubin Crystals
- can be normal in dogs due to renal threshold for bilirubin
- Increased indicates liver disease
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Ammonium Biurate Crystals
- Due to increased excretion of uric acide in urine, this is normal in dalmations and primates
- In all others can indicate portosystemic shunt and liver disease
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Cystine crystals
- Never normal
- Most common in dachshunds
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Tyrosine and Leucine Crystals
- Never normal
- Usually indicates severe liver disease
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Uric Acid Crystal
- Normal in dalmations
- Very little clinical significance
- Form as urine stands or if temperature fluctuates
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Cholesterol Crystals
- Can be normal
- Can indicate severe kidney disease
- RARE
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Urine Casts
- Recorded in #/LPF
- Form in lumen of distal renal tubules
- Tamm-Horsfall protein forms a gelatin mold
- Degenerate urine
- Need more acidic urine
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Hyaline casts
- 1-2/LPF normal
- Colorless
- parallel sides and rounded ends, cylinder shaped
- Easily missed
- Increased with fever, strenuous exercise, mild renal irritation
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Granular casts
- 1-2/LPF normal
- Increased numbers can indicate nephritis
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Cellular casts
NEVER normal
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Erythrocyte casts
- RBCs incorporated into the Tamm-Horsfall protein.
- Deep yello to orange
- Indicates bleeding in kidneys or pathologic
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Leukocyte casts
- WBC in the tamm-horsfall protein
- Disorganized arrangement
- Indicates inflammation most likely due to pylonephritis
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Eputhelial Cell Casts
- Contain renal tubular epithelial cells
- hard to distinguish from WBC casts
- More organized arrangement of granules
- Indicates renal tubule damage
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Fatty Acid Casts
- Contain fat droplets
- DM or high fat diets
- More common in cats
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Waxy cast
- Rare
- broader, square ends
- more opaque then hyaline casts
- Indicates chronic severe degeneration of renal tubules
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Nidus
- Something upon which a stone can form on
- Bacteria, crystals, suture, etc...
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Acidic urine = _______ uroliths
Oxalate
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Alkaline urine = ___________ uroliths
Struvite
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Triple Phosphate Stones
- Most common in dogs and cats
- Alkaline urine
- Secondary to bacterial infection
- Converts urea to ammonia wich increases pH
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Urate/Ammonium Urate Stones
- Uric Acid Stone
- Common in dalmations
- Restrict protein
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Calcium Oxalate Stones
- Hard stones with sharp protrusions
- Can damage the bladder
- Acidic urine
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Azotemia
Increase in non-protein nitrogenous wastes in blood (BUN/Creatinine)
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BUN
Measures level of urea in blood and therefor measures glomerular filtration
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Normal BUN
- dogs 7-27 mg/dl
- cats 16-36 mg/dl
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Increased BUN
- Azotemia
- increased protein diet
- increased breakdown of body protein
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Decreased BUN
- liver disease
- Young animals
- Diuresis
- Starvation
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Creatinine
Test measures level of creatinine in blood and measures flomerular filtration
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Normal creatinine
- dogs 0.5-1.8 mg/dl
- cats 0.8-2.4 mg/dl
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Increased creatinine
Azotemia
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Decreased Creatinine
Diuresis
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Pre-renal azotemia
- Problem is BEFORE kidney
- Concentrated urine thus kidney is workin
- Increased BUN
- Increased Creatinine
- Increased USG
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Primary Renal Azotemia
- Problem is with kidney
- Dilute urine
- 2/3-3/4 nephrons non functional due to age, nephrotoxins, lead and arsenic, drugs, and snake venome.
- Filtration and function do not work
- Increased BUN and Creatinine
- FIXED USG
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Post-renal azotemia
- Probles is AFTER kidney
- Increased BUN, Creatinine, and USG
- Concentrated urine
- Urinary obstruction/rupture
- Emergency - can back up and cause primary azotemia
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