Urinalysis Flashcards
What does the colour indicate in a urine sample?
Concentration and possible pathologies (blood, myoglobin)
What does the smell indicate in a urine sample?
Possible pathologies
What does the turbidity indicate in a urine sample?
Reflects suspended substances (crystals or cells)
Graded from 0 to 4+
Is horse urine naturally turbid? if so, why?
Yes, due to the natural Calcium carbonate crystals and mucus found in their urine
What is the Specific Gravity of a urine sample?
Ratio of weight (density) of urine to that of an equal volume of water at the same temperature
- It is a test of renal tubular function
What values should you always evaluate SG with?
Hydration status: PCV and TP
Serum Urea/ Creatinine
Define Isosthenuria
A urine SG between 1.008 - 1.012
Define Hypersthenuria
A urine SG above > 1.012
Define Hyposthenuria
A urine SG below < 1.008
What are the causes of a low SG?
Polydipsia Iatrogenic Endocrine Diuretic therapy Renal disease
What test can be done if you want to examine the animals ability to concentrate its urine?
Water Deprivation Test
Interpretation of results:
- If urine SG increases to 1.020, tubular function and ADH availability are confirmed
- If urine SG remains <1.020, diabetes insipidus is suspected
The Protein parameter on a Dipstick measures what protein?
Albumin
Trace of 1+ protein in the urine can be normal if _______
if urine SG is high
What other parameters should be taken into account when measuring Protein on a Dipstick?
Urine SG
Serum Albumin
What causes increased protein in the urine ?
Inflammation
Infection
Haemorrhage
Protein losing Nephropathy (glomerular damage)
When proteinuria is found on a dipstick, what should be evaluated next?
Urine Protein to Creatinine Ratio
UPC <1.0 = not significant
UPC 1-2 = urogenital haemorrhage, inflammation or glomerular protein loss
UPC >2 = usually glomerular protein loss
Why might Glucose be found in the urine?
- Diabetes mellitus
- Stress
- Cystitis in cats
- Severe exertion or tremors
- Drugs (Rompun and Ketamine)
- Fanconi Syndrome
In what species are ketones normally found in the urine?
Rabbits only
all other species shouldn’t have ketones in the urine
Why might be the reason for Ketones in the urine?
- Diabetes mellitus
- Pregnancy toxemia in Sheep
- Ketosis and fatty liver in cattle
- Secondary to anorexia, starvation and other illnesses
Why might blood be found in the urine?
- Catheterization or cystocentesis contamination
- Estrus
- Trauma
- Coagulopathy
- Urogenital Inflammation or neoplasia
Why might Hemoglobin be found in the urine?
- Acute Hemolysis
- Bacillary Hburia
- Cu toxicity
Why might Bilirubin be found in the urine?
- Healthy dogs can have 1+
- Icterus: pre-hepatic, hepatic and post-hepatic
Which measurements on a Dipstick are considered variable/ Inaccurate in animals?
- Nitrite
- WBC’s
- SG
- Urobilinogen sometimes: presence of Urobilinogen confirms patency of bile duct and that bile is entering the intestine
Why might Urea be increased in a serum/ plasma sample?
- Prerenal, renal or postrenal problems
Uremia is a clinical syndrome due to reduced renal excretion of toxic substances
Why might Urea be decreased in a serum/ plasma sample?
- Protein deficient diets/ malabsoprtion
- Decreased Liver Function: PSS or Heptaic Insufficiency
- Overhydration
- Young animals
Blood Urea should also be evaluated with ______?
Creatinine and Urine SG
What is the source of creatinine in a blood sample?
Spontaneous degredation of creatine in the muscle
Why might increased levels of creatinine occur in a blood sample?
- Renal disease
note: 80-90% of nephrons must be lost for creatinine to rise significantly
What are the causes of pre-renal azotemia (increased urea and creatinine in blood)?
- Decreased renal perfusion: urea high
- Hemoconcentration, endotoxemia, reduced cardiac output or shock: urea high, creatinine normal, SG increased
- high protein diet or GI haemorrhage: urea high, creatinine normal
A dog has increased serum urea/creatinine and a SG > 1.030, what should be considered?
Pre-renal disease
A dog has increased serum urea/creatinine and a SG between 1.008-1.012, what should be considered?
Primary renal disease
A cat has increased serum urea/creatinine and a SG > 1.035, what should be considered?
Pre-renal disease
A cat has increased serum urea/creatinine and a SG between 1.008-1.012, what should be considered?
Primary renal disease
A horse has increased serum creatinine and a SG > 1.025, what should be considered?
Pre-renal disease
A horse has increased serum creatinine and a SG between 1.008-1.012, what should be considered?
Primary renal disease
Ketonuria is not a sign of renal pathology but is an indication that _____
the renal threshold for ketone bodies has been exceeded, and therefore are leaking into the urine from the blood
Urine bilirubin should always be evaluated with?
Serum bilirubin, urine SG and other physical findings/ history
What is the urine sediment examined for?
- White cells
- Red cells
- epithelial cells
- crystals
- casts
- bacteria
- fat
- Miscellaneous: sperm, fungi
> 5 WBC’s per high power field (40x objective) are seen on urine sediment, what does this suggest?
inflammation of the urinary or urogenital tract
This is considered to be an active sediment
The presence of bacteria along with white cells in urine sediment suggests?
Bacteral UTI
A urine sample collected by cystocentesis shows the presence of bacteria, but no white cells. What does this suggest?
- Possible contamination
- Conditions such as hyperadrenocorticism and diabetes mellitus: these can result in a poor inflammatory response to infection and thus White cells may not be found
A cat presents with blood in the urine, urinalysis shows the presence of blood cells, no white cells and 3+ struvite crystals, what does this suggest?
Feline Lower Urinary Tract Syndrome (FLUTD)
this is a syndrome with several potential causes: urolithiasis, urethral obstruction, urinary infection with a poor immune response, feline idiopathic cystitis, and even diabetes and hyperthyroidism
The presence of squamous cells means?
Not much, they can come from the vulva, prepuce or skin
The presence of a few transitional cells means?
Not much, they can be found in normal healthy animals as the distal urinary tract sheds
The presence of lots, varied size, and clumped transitional cells suggests?
Transitional Cell Carcinoma
What are urinary casts?
Tiny tube-shaped particles, that can be made up of white blood cells, red blood cells, kidney cells, or substances such as protein or fat
note: they are tube-shaped because they maintain the shape of the tubules
Whatever particle is contained in a cast comes from the KIDNEYS
Where are urinary casts formed?
Distal tubules and collecting ducts
What are Hyaline casts, and what do their presence suggest?
These are smooth, round-ended and acellular, which contain mucoproteins
They suggest protein loss
What are Waxy casts, and what do their presence suggest?
fine, granular, degenerating epithelial cells
They suggest tubular injury: ischemia, infarction or nephrotoxicity usually
What are Red Blood Cell casts, and what do their presence suggest?
red cells clumped together
Suggestive of glomerular injury
What are White Blood Cell casts, and what do their presence suggest?
white cells clumped together
Suggestive of pyelonephritis or glomerulonephritis
Is it normal to find crystals in the urine of all species?
Yes
What crystals are common to find in acidic urine?
Calcium oxalate dihydrate
What crystals are normal to find in birds and reptiles?
Urates
What crystals are common to find in alkaline urine?
Phosphate/ Struvite
Healthy horses and rabbits with a significant portion of hay in their diet are expected to find ______ crystals in their urine
Calcium Carbonate
Bilirubin crystals can be normally found in what species?
Bilirubin crystals are not normal in what species?
Normal to find in dog urine in small quantities
Abnormal to find in all other species, and thus hyperbilirubinemia must be explored in these species e.g. IMHA, intravascular hemolysis, bile duct obstruction
Must always be examined with serum bilirubin
Ammonium urate crystals may be seen in which species, and why?
Dalmations, English bulldogs: due to hereditary defect in purine metabolism
Other breeds of dogs raises concerns as it suggests liver disease or PSS, and a need for ammonium to be excreted
The presence of Calcium Oxalate dihydrate crystals (maltese cross) suggests?
Cows, horses and cats: normal
Dogs: hyperparathyroidism or a genetic defect found in Schnauzers
The presence of Calcium Oxalate monohydrate crystals suggests? (long, 6-sided and sharp edges)
Ethylene glycol poisoning
The presence of Calcium Oxalate monohydride crystals suggests? (oval, dumbell form)
Chocolate poisoning in dogs
Which crystal types will you find in liver disease or PSS?
- Leucine (square)
- Cystine (hexagonal)
- Tyrosine (needle-shapes)
- Ammonium biurate
A brown discoloration to the urine might be caused by?
Endogenous: myoglobinura, porphyria
Exogenous: metronidazole, nitrofurantoin
A red discolouration to the urine might be caused by?
Endogenous: hemoglobinuria, hematuria
Exogenous: warfarin, rifampin
A yellow discolouration to the urine might be caused by?
Endogenous: bilirubinuria
Exogenous: riboflavin
A black discolouration to the urine might be caused by?
Endogenous: melanuria
A blue-green discolouration to the urine might be caused by?
Exogenous: methylene blue, doxorubicin, triamterene
What gives urine its normal yellow-ish colour?
- Urochrome: which gets darker as it ages
- Urobilin: breakdown product of Hb
- Uroerythrin: metabolism of melanin
- Uroporphyrins: breakdown of Hb
- Trace levels of Riboflavin
What are the possible causes/ differentials that might cause an abnormal colour?
- diet
- errors in metabolism
- rhabdomyolysis
- medications
- hemolysis
- metabolic defect
- environment
- hematuria
What might you see on urine cytology if renal hematuria is suspected?
- Distorted RBC’s: target cells (doughnut shape) and blebs
- +/- RBC casts
What are the differentials when renal hematuria is present?
- renal trauma
- renal calculi
- acute renal failure
- coagulopathy
- thrombocytopenia
- acute pyelonephritis, glomerulonephritis
- renal neoplasia
- parasitism
- renal cysts
- renal infarcts/ embolism
A urine sample is spun down and the urine appears orange-red to brown (mahogany brown), what might this be indicative of?
Myoglobinuria: damage to the myocytes (muscles)
A urine sample is spun down and the urine appears red to red-brown (port wine red), what might this be indicative of?
Hemoglobinuria:
- IMHA
- Red maple toxicity in horses
- Onion/ chive/ leek/ garlic ingestion in all species
- Cu toxicity in sheep
- Zinc toxicity in dogs: eating US pennies
- Acetominophen in dogs and cats
- Babesia or Lepto
How can you tell between hemoglobinuria, hematuria and myoglobinuria?
- Dipstick:
- Speckled colour change = intact red cells
- Uniform colour change = Mburia or Hburia
- If Hburia is due to Hbemia, you will see a clear red discolouration in the serum or plasma
- Dark red urine, with NO Hbemia or intact red cells on urine sediment = myoglobinuria
- Dark red urine + elevated CK and AST = myoglobinuria
- Ammonium Sulphate Precipitation Test = positive result means myoglobinuria
If you do a dipstick test on a dark pigmented urine sample, but the dipstick test strip is negative, what is this indicative of?
Pigmenturia due to: porphyria or exogenous pigments (e.g. drugs)
If Melanuria is seen (dark black pigmented urine), what is this indicative of?
A rare metastatic malignant melanoma
What is NOT filtered through the glomerulus of the nephron?
RBC’s and proteins (e.g. albumin)
What is reabsorbed in the Proximal Convoluted Tubule of the Nephron?
- WATER
- Glucose
- Ions (Na+, Cl-, K+, Ca+, Pi)
- Amino acids, + small peptides
- Bicarbonate (~90% reabsorbed)
What is the effect of PTH on the proximal convoluted tubules?
Calcium reabsorption
Pi secretion
What are the 2 hormones that affect the Proximal convoluted tubules?
- Angiotensin II
- Parathyroid Hormone
What is secreted at the level of the proximal convoluted tubules?
- Waste metabolites: urate, bile salts, acids
- Hormones: Epinephrine, prostaglandins
- Drugs and Toxic metabolites:
Oxalate: from ethylene glycol poisoning
Diuretics: to enable their effect on renal transports on the lumenal side of the tubule cells
Antibiotics
What is reabsorbed at the level of the Descending loop of Henle?
Water
What is reabsorbed at the level of the Ascending loop of Henle?
Na+
Cl-
What hormone affects the Ascending loop of Henle?
Angiotensin II
Furosemide exerts its effect on the ___________ of the Nephron by?
- Affects the Ascending Loop of Henle (loop diuretic)
- Inhibits luminal Na-K-Cl cotransporter causing Na, Cl and K loss into the urine
What is reabsorbed at the level of the Distal Convoluted Tubule?
- Water
- Ca+
- Na+
- Cl-
Thiazide diuretics exert their effect on the ___________ of the Nephron by?
- Distal Convoluted Tubules
- Blocking Na-Cl cotransport, causing lack of Na+/Cl- reabsorption
Where in the Nephron does Angiotensin II exert its effect?
- Efferent renal capillary
- Proximal Convoluted tubule
- Ascending loop of Henle
- Distal Convoluted tubule
Where in the Nephron does Aldosterone exert its effect?
Distal Convoluted tubule
Where in the Nephron does ADH exert its effect?
- Distal convoluted tubule
- Collecting Ducts
Where in the Nephron does Atrial Natriuretic Peptide exert its effect?
- Afferent renal capillary
- Distal convoluted tubule
What is the effect of Angiotensin II on the Nephron?
Synthesized in response to BP drop
- Increase efferent arteriole constriction
- Increase GFR
- Increase Na+ reabsorption
- Increase circulating volume
What is the effect of Atrial natriuretic peptide on the Nephron?
Secreted in response to increased atrial pressure
- Increases GFR
- Increases Na+ loss and subsequent volume loss
What is the effect of Aldosterone on the Nephron?
Secreted in response to decreased blood volume and increased plasma [K+]
- Increases Na+ reabsorption
- Increases K+ secretion
- Increases H+ secretion
What is the effect of ADH on the Nephron?
Secreted in response to increased plasma osmolarity and decreased blood volume
- Increases the number of aquaporins and subsequent water reabsorption
