Clinical pathology

Question 1

Four things that could increase blood [urea] other than renal disease.

Answer 1

1. High protein diet
2. Dehydration and associated reduced GFR
3. GIT haemorrhage
4. Protein-losing enteropathy

Question 2

Two post-renal causes that could increase blood [urea] and how.

Answer 2

1. Obstruction - urine remains in collecting ducts and pelvis for longer due to increased hydrostatic pressure of the filtrate; more urea gets reabsorbed
2. Uroabdomen - urea equilibrates very quickly with the blood and tissues from the peritoneal fluid.

Question 3

Is urea useful in large animals?

Answer 3

No - it may be within range even in severe kidney disease. Better to use creatinine.

Question 4

Three things that may cause creatinine to be high in the blood other than reduced GFR?

Answer 4

Large muscle mass
Rhabdomyolysis
Training

Question 5

Two things that might increase SDMA other than renal disease.

Answer 5

Hypovolemia
Dehydration
- anything that reduces GFR will increase SDMA!

Question 6

What is the effect of proteinuria and glucosuria on USG?

Answer 6

Each 10g/L increase in these will increase USG by 0.004

Question 7

What are the values for isosthenuria, hyposthenuria, hypersthenuria?

Answer 7

Hyposthenuria USG = < 1.008
Isosthenuria USG 1.008 - 1.012
Hypersthenuria USG > 1.012

Question 8

What are the two broad mechanisms for post-renal disease?

Answer 8

Obstruction or breach of the lower urinary tract

Question 9

What is the likely behaviour of blood potassium in anuric, oliguric disease or obstruction?

Answer 9

Likely rise (hyperkalaemia) due to reduced GFR (either increased hydrostatic pressure of filtrate or other reason)

Question 10

What is the likely behaviour of blood potassium in polyuric disease?

Answer 10

Likely fall (hypokalaemia) due to reduced tubular function or increased flow rate being too fast for them. Also get extra secretion in the collecting duct when the electrochemical gradient is larger.

Question 11

What is the likely behaviour of blood phosphate if GFR is reduced?

Answer 11

It will increase (hyperphosphatemia) as normally 10% is excreted in the urine, and the rest is re-absorbed from the filtrate. Decreased GFR = slower flow rate = more PO43- reabsorbed.

Question 12

What are two potential causes of high blood phosphate other than reduced GFR?

Answer 12

Haemloysis in the sample
Young patient (lots of bone turnover)

Question 13

What is the common behaviour of blood phosphate in horses with chronic kidney disease?

Answer 13

Goes down (opposite to other species)

Question 14

What is the usual behaviour of blood calcium in small animals with chronic renal disease?

Answer 14

Usually low. Very rare to be high.

Question 15

What is the usual behaviour of blood calcium in small animals with acute renal disease?

Answer 15

May be normal, high or low. Sometimes high due to failure to excrete calcium.

Question 16

What is the usual behaviour of blood calcium in horses with renal disease?

Answer 16

Usually high, no matter if acute or chronic.

Question 17

What is the usual response of blood Mg2+ when GFR has been reduced (e.g parenchymal damage to kidney, increased hydrostatic pressure of filtrate, low blood volume)

Answer 17

Increase due to retention, as Mg2+ is usually reabsorbed by the tubules, though there are exceptions.

Question 18

What is the usual behaviour of blood Na+ in cattle with renal failure?

Answer 18

Often decreases

Question 19

What are three differential diagnoses for marked hyponatremia + hypochloremia + azotemia?

Answer 19

Addisons: no aldosterone so no salt being reabsorbed; low electrolytes plus destruction of the medullary interstitial concentration gradient leading to polyuria
Diabetes insipidus: no ADH, so significantly less water being reabsorbed, electrolytes lost in increased flow rate
Severe GIT disease: low Cl from vomiting, low Na from secretion into lumen, azotemia from reduced GFR in response to low blood volume.

Question 20

What does secretory acidosis refer to?

Answer 20

Dysfunction of the renal tubular HCO3- reabsorption

Question 21

What are three mechanisms for anemia in chronic renal failure?

Answer 21

Reduced EPO production due to reduced functional capacity of the kidneys
Reduced life span of RBC due to circulating uremic toxins

Question 22

List three conditions where physiological increase in glomerular permeability may occur, resulting in proteinuria.

Answer 22

Fever
Dehydration
Exercise

Question 23

What are the three main renal mechanisms of proteinuria?

Answer 23

Physiological increase in permeability

Glomerular disease (mostly albumin lost, tends to produce greater proteinuria than tubular disease)

Tubular disease (albumin + other proteins lost, search for electrolyte disorders and glucosuria)

Question 24

What are the three major post-renal mechanisms of proteinuria?

Answer 24

Inflammation of the urinary tract

Haemorrhage into the urinary tract - coagulopathy, uroliths, neoplasia, FLUTD

Genital tract addition - prostatic, vaginal, uterine disease

Question 25

When might you get a false positive for protein on the urine dipstick?

Answer 25

When the urine is extremely alkaline - especially herbivores

Question 26

What are the UPC values that determine normal, borderline proteinuria, significant proteinuria, and likely glomerular proteinuria?

Answer 26

Less than 0.5 = normal animal 0. 5 - 1.0 = borderline proteinuria 1. 0 or more = significant proteinuria Greater than 3.5 - likely glomerular proteinuria

Question 27

What is the term for leukocytes in urine?

Answer 27

Pyuria

Question 28

What is the term for casts present in urine?

Answer 28

Cylinduria

Question 29

What might cause gross brown urine discolouration?

Answer 29

Myoglobin, bilirubin, old haemorrhage

Question 30

What might increased cloudiness of urine reflect?

Answer 30

Mucous, cells, crystals, bacteria | Or storage in cold temperature

Question 31

What is one downfall of cystocentesis or catheterised urine collection?

Answer 31

- requires special skillset, must be sterile | - may get blood contamination

Question 32

What is the normal USG range for a cat?

Answer 32

1.035 - 1.060 /// 1.035 if concentrated

Question 33

What is the normal USG range for a dog?

Answer 33

1.015 - 1.045 //// 1.030 if concentrated

Question 34

What is the normal USG range for a horse?

Answer 34

1.015 - 1.030 //// 1.025 if concentrated

Question 35

What are four things that can increase USG?

Answer 35

Glucose Protein Turbidity Electrolytes

Question 36

What are the normal UPC values for dog and cat?

Answer 36

Dog < 0.5 Cat < 0.4

Question 37

What does UPC result of >1 suggest? | What about >3.5?

Answer 37

> 1 = significant protein loss - renal proteinuria | > 3.5 = most likely glomerular than tubular disease e.g glomerular amyloidosis

Question 38

What are the potential causes of glucosuria in a cat?

Answer 38

Hyperglycemia Tubular disease Stress (can go up to 20mmol/L)

Question 39

What are the normal glucosuria values for cats, dogs, horses, cows?

Answer 39

Dogs: ~ 10mmol/L Cats: ~ 15mmol/L Horses: ~ 9mmol/L Cattle: ~ 5mmol/L

Question 40

How could one animal have ketonuria but not ketonaemia?

Answer 40

Because the dipstick measures different ketones to the blood test - dipstick = acetoacetic acid + acteone - blood test = beta-hydroxybutyrate Ketonuria usually precedes ketonaemia

Question 41

Is it normal to see any bilirubin in dog urine? What about cats?

Answer 41

Dogs can conjugate bilirubin in their tubules - yes small positive is okay, especially if concentrated In cats, bilirubinuria is always indicative of bilirubinaemia. May appear before bilirubinaemia.

Question 42

What does the blood section of the dipstick react with? How can you differentiate which compound is present in the urine?

Answer 42

Haemoglobin, myoglobin and intact erythrocytes Do sediment > RBC? Observe spun urine > red? CBC results > high or low PCV? Check CK in blood , which will be increased in myopathy

Question 43

What might lead to artefactural increase in urine pH?

Answer 43

Storage

Question 44

What might lead to pathological increase in urine pH?

Answer 44

Urease + bacteria

Question 45

Count cells in sediment per 'high power field' | What is the normal range for RBC and WBC?

Answer 45

Less than 5 per HPF

Question 46

What is normal dog and cat urine pH?

Answer 46

Around 7

Question 47

Which species commonly has a lot of lipid in urine?

Answer 47

Cats

Question 48

What is a urinary cast?

Answer 48

An accumulation of protein or cells in the renal tubule due to slow flow +/- tubular damage

Question 49

What does a cellular cast signify? List cellular > waxy in the correct order from youngest to oldest.

Answer 49

Cellular cast = fresh tubular damage | Cellular > coarsely granular > finely granular > Waxy

Question 50

What is a hyaline cast made of? What does it signify?

Answer 50

Normal Tamm-horsfall protein | Slow flow through tubules and/or increased protein leakage

Question 51

What are four physiological causes of a hyaline cast?

Answer 51

1. Strenuous exercise 2. Dehydration 3. Oliguria 4. Proteinuria

Question 52

What does a granular cast contain? What does it indicate?

Answer 52

Mucoprotein, plasma, protein, cells | Indicates renal tubular necrosis

Question 53

What does a waxy cast contain? What does it indicate?

Answer 53

Is a degenerating cellular or granular cast | Oliguria, nephron obstruction, chronic renal failure, end stage renal disease

Question 54

Name three crystals that precipitate in acidic urine

Answer 54

Calcium oxalate Uric acid Bilirubin Cysteine

Question 55

Name three crystals that precipitate in alkaline urine

Answer 55

Calcium carbonate Ammonium biurate Magnesium ammonium phosphate (struvite)

Question 56

Which are the rooftop crystals? Normal? Acidic or alkaline urine? Visible on xray?

Answer 56

Magnesium ammonium phosphate Normal Alkaline No not visible on xray

Question 57

Which are the jacket studs? Normal? Acidic or alkaline urine? Visible on xray?

Answer 57

Calcium oxalate dihydrate Normal in low numbers Acidic urine Yes visible on xray

Question 58

Which are the cucumbers? Normal? Acidic or alkaline urine? Visible on xray?

Answer 58

``` Calcium oxalate monohydrate ABNORMAL Indicate acute renal oxalate nephrosis Form in acidic urine Yes visible on xray ```

Question 59

Which are the muddy spheres? Acidic or alkaline? Normal? Visible on xray?

Answer 59

Calcium carbonate. Normal in horses, rabbits (give cloudy mucoid appearance). Alkaline urine Yes visible on xray- anything with calcium is

Question 60

Which are the fireworks? Normal? Acidic or alkaline urine? Visible on xray?

Answer 60

Bilirubin crystals - low numbers okay in dogs, abnormal in cats - indicates bilirubinaemia Acidic urine Probably not visible on xray

Question 61

Which are the sarcoptes crystals? Normal? Acidic, alkaline?

Answer 61

Ammonium biurate - abnormal in most species except some dogs, where they may just be due to defect in purine metabolism. Though they can indicate hepatic insufficiency. Form in alkaline urine. Dog breeds that may have them in health include English bulldogs, dalmatians, black russian terrier

Question 62

Which are the hexagons/pentagons? Normal? Acidic or alkaline?

Answer 62

Cysteine crystals - never normal - indicate inability to reabsorb cysteine at PCT Acidic urine

Question 63

What might fungal hyphae signify in sediment?

Answer 63

Infection or sample contamination

Question 64

If you get positive protein in a urine sample >8 pH what does this signify?

Answer 64

Could be false positive - search for inflammation, if none, run UPC, if none, then was false positive likely.