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3 factors if urine composition
- quantity/composition of plasma presented to kidney
- renal function (filtration, tubular secretion/absorption)
- materials added to glomerular fluid from kidneys, ureters, bladder, urethra, and prepuce/vagina/vulva
4 methods of collection
- midstream catch
- manual expression (not recommended, damage or increase RBC)
Voided sample of urine
- free catch, midstream preferred.
- Preferred method for large animals.
- bacteria (genital vs UTI), epithelial cells, spermatozoa, and leukocytes in sample.
- preferred method in small animals and for urine culture.
- Danger of iatrogenic hemorrhage and accidental enterocentesis (bowel loop over bladder). Can also cause increase in RBCs
Catheterized collection of urine
commonly contaminated by epithelial cells, blood from iatrogenic hemorrhage, lubricant and bacteria
why fresh urine preferred
- Should be within 30 minutes.
- Urea hydrolysis becomes ammonium, increasing pH of urine, which can break down casts or cells. Oxidation can make in vitro crystals, overgrowth of bacteria can also effect ketones and glucose. Urine can change color.
- 3 hours max, refrigerate after 30 minutes.
- Can add chemical preservatives
- warm to room temp before evaluation (redissolve precipitates and enzymes will function properly)
4 parts of urinalysis
- visual inspection (color, transparency, odor)
- chemical analysis (protein, glucose, ketones, etc)
- specific gravity (refractometer)
- microscopic sediment (RBC, WBC, bacteria, crystals, casts
Chemical analysis of urine
- commercially available dipsticks (multistix, chemstrip), at room temp.
- semiquantitative eval (+1, +2 etc)
dipsticks test for (10)
- glucose (changeable, old strips wrong)
- specific gravity (always wrong)
- blood (not specific, RBC hemoglobin or myoglobin)
- urobilinogen (some normal, unstable so false-)
- Nitrate (false-)
- leukocytes(must use slide)
Error in dipsticks
- susceptible to moisture
- limited shelf life
- affected by pH of urine or substances
- reagent pads contaminated (tech fingers)
- reading at wrong times
- holding vertically, leakage
- pigmented urine
- urine too cold (fridge)
- spin low and slow, remove supernatant (specific gravity and chem with supernatant)
- drop to slide, cover slip.
- examine at 10x and 40x. NO OIL FOR URINE
Normal urine output for d/c vs polyuria
- normal: 20-40ml/kg/day
- Polyuria: usually not counted until double, so 80ml/kg/day. Indicates upper UTI.
- Be sure not to confuse with pollakiuria, which indicates lower UTI.
Causes of polyuria
- increased consumption, diuretics, IV fluids or steroids non pathogenic.
- Diabetes mellitus (insulin)*
- diabetes insipidus (aldosterone)
- Chronic Renal disease*
- liver disease
- psychogenic polydipsia
- lower water intake, higher temp, hyperventilation nonpathological.
- acute renal failure
- low blood pressure
red or reddish brown urine
- Spin sample, RBC will settle so if does not clear, hemo or myo.
dark brown or black urine
methemoglobinuria. Tylenol toxicity in cat.
yellow brown to green brown urine
concentrated sample, bilrubin or pseudomonas
normal causes of cloudy urine
- normal for horse (calcium carbonate crystals and mucus)
- normal for rabbit (calcium carbonate crystals, appears milky)
- cats have fat globules
- standing urine and refrigeration can cause crystallization.
Cloudy urine can have
- WBC, RBC, epithelium, casts, crystals, mucus, fat, bacteria, sperm
- contamination from container
- contamination from feces
Odor of urine
- can be species and gender dependent (male intact)
- ammonia odor caused by UTI or urease-producing bacteria
- sweet or fruity odor caused by ketones. Diabetes mellitus, ketosis in cows, pregnancy toxemia in ewes and cows.
- ratio of the weight of urine compared to the weight of water
- determined by the number and molecular weight of dissolved solutes
- inversely related to volume (oliguria has high SG, poluria has low SG)
- reflects renal function
- measured with refractometer (reagent strips unreliable)
USG of urine depends on
- eating and drinking habits
- environmental temperature
- timing of sample (morning most concentrated)
- Variable. Fluctuates throughout the day.
Diabetes mellitus USG
increase of glucose in urine causes high specific gravity because it's a big molecule, but diabetes causes polyuria
End stage kidney failure urine SG
same USG regardless of volume of urine
- > 1.030 for a dog
- > 1.035 for cats
- > 1.025 for horse/cow
- Filtrate has been concentrated by renal processes
- < 1.008
- filtrate has been diluted by renal processes (working)
- USG approaches that of glomerular filtrate
- neither concentrated nor diluted by renal processes
pathological and nonpathological causes of USG hypersthenuria
- nonpathological: decreased water intake, increased fluid loss (sweat, panting, VD), increased excretion of urine solutes (high environmental temp or hyperventilation)
- Pathological: dehydration, fever, diabetes mellitus, protein, glucose or cells in urine
pathologial and nonpathological causes of hyposthenuria
- nonpathological: excess water consumption, diuretics, IV fluids, steriods (exogenous or endogenous)
- Pathological: diabetes insipidus (kidneys don't respond to ADH), pyometra, psychogenic polydipsea, cushings
pathological and nonpathological causes of isostenuria
- persistent isosthenuria indicates primary renal disease (single sample nondiagnostic)
- Isosthenuric urine + dehydration + azotemia = renal disease
- measured with reagent strips or pH meter
- 7 = neutral
- >7 = alkaline
- < 7 = acidic
- Depends on species, stress, and diet
diet and pH
- plant material causes alkaline urine (herbavores)
- meats and dairy cause acidic urine (carnivores)
- Omnivores depend on what they ate
pH of stress/excitment
usually increases (alkaline), especially cats.
Normal pH of urine of cat, dog, horse, cow
- Dog: 6-7
- Cat: 6-7 (usu lower than dog)
- horse: 7-8.5
- cattle: 7-8.5
Causes of alkaline urine
- veggie based diet
- UTI (urease + organisms)
- administration of alkaline agents
- metabolic/respiratory alkalosis
- postprandial (alkaline tide, response when H+ all goes into stomach)
- distal renal tubular acidosis
- urine allowed to stand open at room temp (CO2 lost , blows off
Causes of acidic urine
- meat-based diet
- administration of acification units
- metabolic or respiratory acidosis
- chloride depletion
- protein catabolism
Reagent strip protein
- dilute urine causes false neg.
- changes in color pad to correspond to expected, raped, convenient, reasonable accurate
- abnormal urine color may interfere
- alkaline urine causes false positives (protein)
- Primrily detects albumin
SSA turbidity in protein
- Sulfosalicylic acid
- sensitive to albumin and GLOBULIN (better than strip)
- proteins are denatured by acids, form a precipitate which increases turbidity.
- Turbidity proportional to protein
- Semiqualitative (+1, +2, etc.)
- qualitative, confirms proteinuria, sign of renal before 75% loss/azotemia.
- Not affected by concentration or volume (low USG=false on strip)
- Healthy dog <0.2
- renal >0.5
- questionable in between
physiologic (nonpathogenic) proteinuria
- circumstantial, often transient
- renal vasoconstriction, ischemia, congestion
- excessive protein intake
- strenuous exercise
- temperature extremes
Prerenal pathological proteinuria
- increased plasma concentration of small proteins that pass through glomerulus (excess, some absorbed in glomerulus)
- young neonates, w/in 24-40 hours
- Bence-Jones proteins (paraproteins, multiple myeloma)
- hemoglobin (Intravascular hemolysis)
- myoglobin (severe muscle injury, rhabdomyolysis)
glomerular renal proteinuria
- from glomerular disease, damaging filtration barrier, usually albumin leaking
- decreases selectivity, increased permeability to large or negative plasma proteins, incomplete resorption
- Glomerulonephritis (UPC 3-5), amyloidosis (UPC ~15)
- Frequently both tubular and glomerular problem together
chronic inflammation which eventually destroys nephron
Disorders causing glomerular proteinuria
- infectious (often tick-borne)
- diabetes mellitus
- pituitary dependant hypoadrenocorticism (PDH)
- hereditary forms
tubular renal proteinurias
- defective proximal renal tubule not resorbing normal proteins. Usually mild, leaking globulin protein.
- Toxicosis (ethylene glycol, aminoglycosides, lead)
- Frequently both tubular and glomerular problem together
- hemorrhage or inflammation
- urethritis (female more than male)
- Trauma (secondary to cystocentesis, catheterization or bladder expression)
Proteinuria false positive causes
Proteinuria false negative causes
- Positive: alkaline urine, disinfectants, pigmented urine, concentrated urine
- Negative: dilute urine, acidic urine
- usually negative unless blood glucose level exceeds renal threshold (rates of glomerular filtration and tubular reabsorption, 170-180 mg/dL)
- IV Dextrose
- excessive glucocorticoids (STRESS in cats)
causes of glucoseuria
- Physiologic hyperglycemia: stress, postprandial, excitement/fright, diestrus
- Pathologic hyperglycemia: diabetes mellitus, pancreatitis, cushings, hyperthyroid
- Renal glucosuria: damaged/abnormal proximal tubule (fanconi syndrome acquired or congenital) previous stress or excitement
Glucoseuria false negatives or positives
- False positives: hydrogen peroxide or bleach
- False negatives: ascorbic acid, high ketones (diabetic ketoacidosis), cold urine, expired reagent strips, formalin vapors
excessive fat catabolism
pathologic state caused by excess ketogenesis
ketosis with acidosis
- excessive ketones in urine caused by burning too much fat.
- undetectable normally. False negatives common due to B-hydroxybutyric acid (use ACE test)
what can screw up all results?
measures all types of ketones, including B-hydroxybutyric acid, which dipsticks don't pick up
ketonuria false positives and false negatives
- false positives: pigmented urine
- false negatives: old urine (30 minutes or 3 hours refrigerated)
Causes of ketonuria
- diabetes mellitus
- starvation (maldigestion/malabsorption, prolonged VD)
- high fat, low carb diet (atkins)
- hypoglycemic disorders (pregnancy disease in ewes and ketosis in cows)
- breakdown product of hemoglobin, conjugated or unconjugated
- Conjugated: conj in hepatocytes, to bile and back into circ, filtered by glomerulus, not resorbed by tubules
- Unconjugated: rare to see, bound to albumin so too big to get into tubules
- dog can be +1 safely.
- From bilirubinemia (hemolysis, biliary disease, hepatic disease, pre-and post)
Pre-hepatic pathologic bilirubinuria
- hemolytic diseases (seen on HCT, regenerative anemia) like IMHA, or infectious like RBC parasites (mycoplasma haemofelis, babesia canis or gibsoni)
- metabolic like heinz body anemia (propylene glycol in cats, onions)
- Traumatic (microangiopathic disease, schistocytes)
hepatic pathologic bilirubinuria
- hepatocellular disease:
- infectious (viral hepatitis, Leptospirosis)
- chronic active hepatitis
- neoplasia of liver
Posthepatic pathologic bilirubinuria
- Cholestasis, could be choleliths or colecystitis.
- Could be anywhere along biliary, often presents with hepatitis (backs up into liver)
- cholangiohepatitis, mucoseal
Positive for occult blood on reagent strip can be
- free hemoglobin
- free myoglobin
RBCs lyse on contact with the reagent pad, causing positive reaction. Lyse required.
Clinical causes/appearance/microscope of hematuria
- bleeding into urinary tract: inflammation, trauma, neoplasia, calculi, coagulopathy
- Looks red, 2-3 RBCs/hpf. Spin, RBC will sink
- RBCs lyse when stored too long, too dilute or alkaline.
hemoglobinuria and clinical causes/appearance/microscope
- Free Hb in urine from hemoglobinemia (won't clear when spun).
- Causes: intravascular hemolysis, toxicity, mechanical damage, infectious damage
- appearance: port wine color to urine
- microscope: lack of RBC, doesn't clear with centrifuge
- Mb in urine as a result of being in blood,
- caused by: excess muscle breakdown, muscle disease or trauma (myocyte injury releases myoglobin)
- filtered by glomerulus
- appearance: dark brown or black
- lab: elevated CK, AST
sedimentation and what you need/do
- centrifuge at low speed
- remover supernatant, drop on slide and examine stained and unstained
- ideally analyze within an hour of collection
normal urine sediment
- not much in domestic animals, includes epithelial cells, mucus, RBCs, WBCs, casts and crystals
- Horses and Rabbits have calcium carbonate crystals, causing cloudy/milky urine
- increased WBCs in urine
- looks cloudy.
- >5/hpf (less is normal)
- Caused by UT inflammation (infection or not), genital catch inflammation (voided sample) or contamination (voided)
WBCs in sediment
- spherical, dull gray or greenish-yellow, granules, lobulated nucleus
- Most are neutrophils
- shrink in concentrated, swell in dilute
- larger than erythrocytes, smaller than renal epithelial cells
- makes urine cloudy
- small amt normal (shedding and replacing), lots means inflammation
- squamous, transitional, or renal
Squamous epithelial cells
- lower urethra and genital tract, mostly only from voided samples.
- Flat, thin, fried-egg, homogenous cells
- largest cells in sediment
transitional epithelial cells
- bladder, ureters, renal pelvis and proximal urethra
- normal in small amounts
- increased from cystitis, pyelonephritis, and catheterization
- Transitional Cell Carcinoma in Westies
Renal epithelial cells
- from renal tubules, very rare (0-1/hpf), increased numbers suggest disease of kidney parenchyma
- smallest epithelial cell, spindle-shaped, round, large nucleus and no to fine granules
neoplastic epithelial cells
- not normal, from tumor usually
- Different sizes, mitotic, basophilic, ropy chromatin pattern
- most common is Transitional Cell Carcinoma in the bladder in Westies
- tubular structures from renal tubules made of protein from plasma, mucoprotein from tubules and cells.
- Classified by appearance
- hyaline or fine granular 0-3/hpf normal, esp after physical activity
- Most significant in dilute urine
- Lots suggest renal lesion in tubules
Types of casts (transformation) and what decides
- which cast develops depends on how quickly filtrate is moving and how much damage.
- hyaline > epithelial (cellular) > coarse granular > fine granular > waxy
- Usually formed more distally where urine is more acidic
Casts and renal disease
- can be disease without casts, particularly in chronic, progressive or generalized nephritis
- shed intermittantly
- unstable in urine, dissolve in time, esp in dilute or alkaline urine (like in renal disease)
- Not reliable for diagnosis
- Regeneration is possible if basement membrane undamaged
- composed of protein only
- clear, colorless, transparent, easier to see in stain or low light
- 0-3/hpf normal
- Caused pathologically by: renal or extra-renal proteinuria, chronic kidney disease, fever, dehydration, strenuous exercise or general anesthesia
- degeneration and necrosis of tubular epithelial cells due to acute tubular injury (ischemia, infarction, nephrotoxicity like grapes)
- Made of RBC, WBC, epithelial cells
- does not tell extent or reversibility of disease
- renal epithelial cells embedded in hyaline matrix
- acute nephritis, ischemia, infarction, toxins
- Hyaline cast (coarse or fine) containing granules from tubular epithelial cells, RBCs and WBCs (cells go into cast then are degraded)
- a few normal, increased due to acute nephritis (more severe than hyaline)
- reflect degeneration/necrosis/inflammation of tubules
- ALWAYS pathologically significant (not diagnostic)
- chronic or severe tubular degeneration.
- Like hyaline but square ends, wider, dull, homogenous, waxy appearance, colorless or gray. Look like ziti
- full of refractile fatty droplets (drops common in cats) in a hyaline or granular background.
- seen in cats with renal disease and dogs with diabetes mellitus.
- lots suggests degeneration of tubules
Bacteria in sediment
- caused by UTI, genital tract infection, invitro growth or contamination.
- normal urine is sterile, some may be in free catch normally
- reported as few, moderate, many, TNTC
- Often seen with increased WBC and RBC (UTI)
- Use cysto for accuracy, then culture and sensitivity
Common bacteria in UTI and how to ID for sure
- E. coli bacilli common (anal contamination).
- Gram stain to be sure of bacteria
- Neutrophil/macrophage can be eating bacteria
yeast and fungi
usually contaminants, could indicate fungal UTI in long-term abx users.
- Ova visible in sediment.
- Capillaria plica most common, capillaria felis-cati and dioctophyma renale
- Could also be fecal contamination (roundworms)
- confused with casts but don't have delineated edges
- lots in equine
- Otherwise urethral irritation or contamination from genital secretions
- occasionally seen in intact males or bred females
- no clinical significance
- may cause protein positive
- fat droplets in urine
- lightly green, highly refractile, spherical bodies of varying sizes (unlike yeast and RBC)
- some in most cats
- caused by: obesity, diabetes mellitus, hypothyroidism and high-fat meal
- may or may not be significant (cold, age), some normal
- Caused by metabolic diseases (shunts cause calcium oxalate)
- type depends on pH, concentration, temperature, solubility
- Occasional, moderate or many (+1 - +4)
crystals that form in alkaline urine
- Triple Phosphate
- Amorphous Phosphate
- Calcium Carbonate
Crystals that form in acidic urine
- Everything not alkaline
- ammonium biurate
- amorphous urate
- calcium oxalate
- uric acid
- triple phosphate, common in d/c with alkaline urine (>/=7)
- Can be caused by urease-producing bacteria UTI
- 3-6 sided prisms, "coffin lids"
- most common
amorphous phosphate crystals
granular precipitates in alkaline urine.
Calcium carbonate crystals
- no clinical significance, appear in alkaline urine and very common in horses and rabbits.
- Dumbell shape or spherical with radiating spokes (pinwheel or diamond)
Ammonium biurate crystals
- acidic urine, seen in healthy (esp dalmations and EBD)
- liver dysfunction, PSS in dog/cat
- brown spheres with long irregular spicules, "thorn apple"
acidic urine, yellow-red granular precipitates. Small numbers normal, large numbers mean faulty uric acid metabolism (Dalmations), portovascular malformation, severe hepatic disease, ammonium urate urolithiasis
Calcium oxalate dihydrate
- acidic urine, common in male dogs, stones.
- Small squares with X, fortune-teller.
- Normal in rabbits, horses, dogs and cats
- caused by: abnormal calcium excretion, ingestion of O2-rich plants, ethylene glycol toxicity (usually mono).
- Large numbers form calculi
calcium oxalate monohydrate
- small and dumbell shaped or elongated and pointed at each end (Picket fence)
- ethylene glycol toxicity
- hypercalcemia (hyperparathyroidism)
Hippuric acid crystals
- very rare, often confused with calcium oxalate monohydrate crystals
- normally found in horses/herbivores
- acidic, neutral or slightly alkaline urine
- acidic. Uncommon.
- Parallellogram with notched corner (broken plate)
- seen in healthy dogs
- hyperhcolesterolemia and proteinuria (protein-losing nephropathy
- acidic urine, rare.
- Flat, hexagonal, colorless, thin, stop-signs
- renal tubular dysfunction (amino acids not resorbed in proximal tubules)
- Cystine urolithiasis seen in dachshunds, newfoundlands, EBD, scottish terriers
uric acid crystals
- colorless, flat and diamond-shaped or 6-sided.
- Seen in dalmations and EBD, almost never otherwise.
- Large numbers could mean liver dysfunction, PSS, faulty uric acid metabolism, portovascular malformation
- yellow to amber pile of twigs or antlers (pick-up sticks)
- low numbers in highly concentrated canine urine.
- Otherwise caused by bilirubinemia (prehepatic, hepatic, posthepatic)