VTNE Review: Urinalysis

free catch

• voided sample

• may include contaminants from the genitalia as the sample passes out of the body

• not useful for culture

• act of urination known as micturition

cystocentesis

• insertion of a needle into the bladder for sterile collection

• samples may contain a small amount of iatrogenic blood when obtained

• preferred method for urine culture

• between the last nipples on midline is the most reliable location for collection

urinary catheterization

sterile procedure to get urine directly from the bladder

color of urine

• normal color is yellow

• if dark or light yellow it is often a reflection of sample concentration or whether it contains pigment such as bilirubin (bright yellow)

transparency

• normal urine is clear in dogs and cats

• in large animals it is more turbid or cloudy

• causes of cloudiness may be from crystals, infection, mucus, casts, sperm, etc

odor

• may smell like ammonia

• in ketoacidosis, the urine may smell like acetone

• foul odor is sometimes noticed if there is bacteria in the urine

• certain medications may cause the urine to have an odor

normal urine production quantity in dogs

12-30 ml per pound normal urine

normal urine production quantity in cats

5-9 ml per pound

normal urine production quantity in cows

8-20 ml per pound

normal urine production quantity in horses

208 ml per pound

normal urine production quantity in pigs

2-14 ml per pound

normal urine production quantity in sheep/goats

4.5-18 mls per pound

urine specific gravity

• used to evaluate the concentration of urine

• normal: 1.025-1.050

• best to perform on a first morning sample

isosthenuria

low urine concentration (1.008-1.012)

hyposthenuria

inability to concentrate urine (less than 1.008)

pH

• test the acidity

• pH less than 7 is acidic; greater than 7 is alkaline

• samples left sitting out may result in increased pH

• often related to diet, medications, or time of collection

protein

• often indicates urinary tract disease, especially renal disease

• may also be positive if contaminants are present in the sample (cells, bacteria)

• may be confirmed by the sulfosalicylic acid test

glucose

• glucosuria occurs when the renal threshold is exceeded (more than 170 mg/dl in dogs)

• most common cause of glucosuria is diabetes

• in cats that are stressed/scared, hyperglycemia may occur, exceeding the renal threshold and may cause glucosuria

• renal glucosuria (which is rare) may also occur due to decreased resorption of glucose in the renal tubule due to kidney disease

ketones

• increased catabolism of fatty acids results in ketonuria

• causes include:

  • pregnancy toxemia: energy requirement for milk production exceeds energy intake and body fat is metabolized, causing ketone production; important cause in cattle and small ruminants

  • diabetes: lack of insulin leads to inappropriate metabolism of carbs such that fat is broken down and ketones are produced

  • starvation or prolonged hypoglycemia, low carb diet, or long standing fever

bilirubin

• may be normal in dogs and cattle

• never normal in cats, pigs, sheep, or horses

• presence suggests biliary obstruction or hemolytic anemia (liver cannot excrete the excess bilirubin which is released from the lysed erythrocytes

• confirmed with the Ictotest

blood

• reagent strip will react to erythrocytes, hemoglobin, and myoglobin

• differentiate these with urine sediment

• erythrocytes suggest bleeding from urinary or genital tract

• hemoglobin suggests intravascular hemolysis

• myoglobin suggests muscle damage

nitrate

positive reaction suggests bacteriuria, but negative does not rule out the presence of bacteria

leukocytes

• more reliable in dogs on a test strip

• false positives very common in cats

• confirm presence of white blood cells on sediemnt exam

• suggest urinary tract infection or inflammation in the urogenital tract

cells found on sediment evaluation

• red blood cells

• white blood cells

• transitional cells (cell type found in the urinary tract)

crystals found in sediment

• calcium oxalate, struvite, urate, bilirubin, cystine

• may be normal in concentrated urine specimens

• animals with ethylene glycol toxicity often have calcium oxalate crystalluria

bacteria on sediment

with presence of leukocytes, infection is likely, or may be from contamination if the sample was voided

• sperm

• in free catch intact male samples or females if recently bred

fat droplets

red blood cells

white blood cells

transitional cells

calcium oxalate

casts

cylindrical mold of renal tubules made of protein or cells

struvite crystals

urate crystals (uric acid crystals)

bilirubin

cystine crystals

hyaline casts

granular cast

cellular cast

renal tubule cast

cocci

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