Urinary System Clinical Pathology

Front 1

What re the 4 functions of the kidneys?

Back 1

1) Regulation of body water, electrolyte, acid-base
2) Hormone production, degradation, excretion
3) Regulate blood pressure
4) Excrete wastes & drugs

Front 2

What 4 things are resorbed in the proximal tubules?

Back 2

1) Na+
2) H2O
3) Glucose
4) Amino acids

Front 3

What is resorbed in the loop of henle?

Back 3

Na+ and water

Front 4

What is resorbed in the distal tubule?

Back 4

Na+/H2O

Front 5

What's resorbed in the collecting tubule?

Back 5

Water

Front 6

What are the 3 basic processes involved in urine formation?

Back 6

1) Glomerular filtration
2) Tubular resorption
3) Tubular secretion

Front 7

Up to 1/3 of the water passing in the blood is filtered through the glomeruli and produces an ________.

Back 7

Ultrafiltrate of plasma

Front 8

What is isosthenuria?

Back 8

Specific gravity coming in to proximal tubule is ~1.008-1.012, do if its the same going out= isosthenuric

Front 9

Where does most tubular reabsorption occur in the nephron?

Back 9

Proximal convoluted tubule

Front 10

What is the renal threshold?

Back 10

The blood concentration of a substance that is higher than what the kidney can handle --> spills into urine

Front 11

What 3 ions/molecules are secreted by the tubules to maintain normal body concentrations?

Back 11

1) H+
2) NH3
3) K+

Front 12

The final concentration of urine occurs in the ______ and _____ under the influence of _____.

Back 12

Distal tubules
Collecting ducts
ADH

Front 13

What happens if there's no ADH in the body?

Back 13

H20 not resorbed, urine dilute--> increased Na+ ---> release of ADH

Front 14

What is renal disease?

Back 14

Any kidney lesion

Front 15

What is renal failure? How much nephron must be lost?

Back 15

Inability of kidneys to perform function, leading to azotemia and failure to concentrate or dilute urine
-Usually requires loss of > 75% nephrons

Front 16

What is azotemia?

Back 16

Increased BUN or creatinine

Front 17

What is uremia?

Back 17

A clinical syndrome involved in renal failure

Front 18

What is pre-renal azotemia?

Back 18

Decreased GFR
Specific gravity concentrated

Front 19

What is post-renal azotemia?

Back 19

Obstruction of outflow
Specific gravity concentrated

Front 20

What is renal azotemia?

Back 20

Renal failure
Specific gravity isosthenuric

Front 21

What is the most common cause of pre-renal azotemia?

Back 21

Dehydration

Front 22

What is GFR?

Back 22

How much glomerular ultrafiltrate is filtered through the glomeruli

Front 23

What are 3 causes of a decreased GFR?

Back 23

1) Decreased renal perfusion (pre-renal)
-Shock, dehydration
2) Renal loss (loss of 75% function)
3) Post-renal (obstruction)

Front 24

What produces urea nitrogen? What excretes it?

Back 24

Liver-protein metabolism
Excreted by kidneys

Front 25

What causes an increase in BUN?

Back 25

Decreased GFR

Front 26

What are 2 causes of decreased GFR?

Back 26

1) Pathologic (Renal disease)
2) Physiologic (dehydratio)

Front 27

Why don't the BUN and creatinine increase in an animal with normal functioning kidneys?

Back 27

Urine becomes concentrated before BUN and creatinine are increased

Front 28

The BUN doesn't increase until _____ of kidney function is gone.

Back 28

3/4

Front 29

There's a loss of concentrating ability when _____ of kidney function is gone.

Back 29

2/3

Front 30

____ may have increased BUN before concentrating ability is lost.

Back 30

Cats

Front 31

What are 2 other causes of increased BUN (especially if creatinine isn't increased)?

Back 31

1) High protein diet
2) Digesting blood (has lots of protein)

Front 32

Why isn't the BUN a sensitive indicator of renal function in bovine?

Back 32

Urea is used in rumen for protein synthesis

Front 33

What are 2 causes of decreased BUN?

Back 33

Liver failure
Low protein diets

Front 34

What are 4 causes of increased BUN?

Back 34

1) dehydration
2) High protein
3) Blood digestion
4) Renal failure

Front 35

What produces creatinine?

Back 35

Produced in muscle from creatine

Front 36

True or false. Creatinine increases with muscle damage.

Back 36

False! CK increases with muscle damage

Front 37

What happens to creatinine when reaching the glomerulus?

Back 37

Freely filtered through glomeruli-not reabsorbed

Front 38

What causes increased creatinine?

Back 38

GFR decreases
-Fewer things affect creatinine than BUN

Front 39

What are 3 more accurate clearance tests not typically performed in clinical practice?

Back 39

1) Inulin clearance
-The gold standard; not metabolized, not bound, rely filtered, not reabsorbed or secreted
2) endogenous creatinine clearance
3) Exogenous creatinine clearance

Front 40

Urine specific gravity is used to help figure out cause of ________.

Back 40

Decreased GFR

Front 41

What is the "normal" urine specific gravity?

Back 41

Depends on hydration status so no normal range

Front 42

____ are normally the best at concentrating urine.

Back 42

Cats

Front 43

Urine specific gravity is a measure of _____ .

Back 43

Urine concentration
-Measures density of urine compared to water

Front 44

How is the specific gravity usually measured?

Back 44

Refractometer

Front 45

If BUN and creatinine are increased, but urine is concentrated, what's the interpretation?

Back 45

Pre-renal problem (though cats in renal failure may retain some concentration ability)

Front 46

If BUN and creatinine are increased and urine is isosthenuric, what's the interpretation?

Back 46

It's probably renal failure

Front 47

If the urine is isosthenuric and no azotemia, what's the interpretation?

Back 47

Could be normal, but remember that concentrating ability is lost before azotemia occurs! recheck

Front 48

What are you going to do if an animal presents with polyuria, isosthenuric urine, but no azotemia?

Back 48

Perform concentrating tests

Front 49

What are 2 concentration tests?

Back 49

1) Water deprivation test
2) ADH response test

Front 50

What normally keeps a water deprived animal from being dehydrated?

Back 50

ADH is released in water-deprived animals, H2O is resorbed, urine becomes concentrated

Front 51

How do you perform a water deprivation test?

Back 51

1) Empty bladder, measure USG
2) Weigh animal, measure BUN/ creatinine
3) Take away water for 12 hours or until:
-Clinical dehydration or
-loss of 5% body weight or
-USG> 1.030 (dog) > 1.035 (Cat) OR
-BUN/ creatinine increase

Front 52

What does it mean if the urine specific gravity doesn't increase adequately before other conditions are met when performing a water deprivation test?

Back 52

-Pituitary isn't releasing ADH= pituitary diabetes insipidus OR
-Renal tubules aren't responding to ADH= Nephrogenic diabetes insipidus

Front 53

What are 4 causes nephrogenic diabetes insipidus?

Back 53

1) Chronic renal disease
2) Hypercalcemia
-Gets too high & concentrates in tubules
3) Medullary washout
4) Psychogenic polydipsia

Front 54

You perform a water deprivation test on an animal and it cannot concentrate the urine, what is your next step?

Back 54

Perform ADH response test

Front 55

What does it mean if an animal cannot concentrate its urine, but can respond to exogenous ADH?

Back 55

Diagnosis is pituitary diabetes insipidus

Front 56

If an animal cannot concentrate its urine with the water deprivation test and the animal does not respond to exogenous ADH, what's the diagnosis?

Back 56

Renal disease, nephrogenic diabetes insipidus or medullary washout

Front 57

What does fractional excretion assess?

Back 57

Renal function

Front 58

What does the fractional excretion measure?

Back 58

Clearance of electrolytes

Front 59

What is the fractional excretion?

Back 59

Proportion of a substance excreted in urine compared with how much is filtered in glomerulus

Front 60

How do you calculate the fractional excretion?

Back 60

By comparing to clearance of endogenous creatinine- expressed as % of creatinine clearance

Front 61

What do you measure to determine the fractional excretion?

Back 61

Serum & urine electrolyte and creatinine e.g. K+
FE= (urinary K+/serum K+) x (serum creatinine/urine creatinine) x 100

Front 62

How does a fractional excretion work, what does it mean?

Back 62

If renal tubules aren't functioning normally, electrolytes aren't resorbed properly and FE will increase. Creatinine is constant so cancels out the effects of urine concentration or dilution

Front 63

What does an increased fractional excretion mean?

Back 63

Usually tubular failure

Front 64

What are 6 common lab abnormalities seen with renal disease?

Back 64

1) Non-regenerative anemia
2) Hyperphosphatemia (hypophosphatemia in horses)
3) Hypocalcemia (hypercalcemia in horses)
4) Hyperkalemia (may see hypokalemia in cats)
5) Metabolic acidosis (increased uremic acids)
6) Increased amylase and lipase

Front 65

What usually causes acute renal failure?

Back 65

Usually toxic or ischemic event

Front 66

What are 2 clinical signs of acute renal failure?

Back 66

Oliguria, anuria

Front 67

What are 4 findings of acute renal failure on biochemical profile and blood gas analysis?

Back 67

1) Azotemia
2) Hyperphosphatemia
3) Hyperkalemia
4) Acidosis

Front 68

What is seen on urine analysis of an animal with acute renal failure?

Back 68

Casts

Front 69

_______ is often seen early after ingestion of antifreeze.

Back 69

Metabolic acidosis

Front 70

Ethylene glycol toxicity has other laboratory abnormalities similar to other cases of acute renal failure, plus what 2 things?

Back 70

1) Hypocalcemia (Calcium bound up in crystals)
2) Calcium oxalate monohydrate crystals in urine (maybe calcium oxalate dihydrate too)

Front 71

How do you tell the difference b/w calcium oxalate monohydrate crystals and struvite?

Back 71

Calcium oxalate don't have 3rd dimensional structures

Front 72

What is the clinical significance of calcium oxalate dihydrate crystals?

Back 72

Common in normal animals

Front 73

You can diagnose ethylene glycol toxicity using a _______ thats available thorugh PRN pharmacal, takes about 6 minutes to run.

Back 73

Specialized test kit

Front 74

What are the clinical signs of chronic renal failure?

Back 74

Polyuria/ polydipsia

Front 75

What are 6 abnormalities seen on the blood work for chronic renal failure?

Back 75

1) Azotemia
2) Hyperphosphatemia
3) +/-hypocalcemia
4) Non-regenerative anemia
5) K+ normal, increased or decreased (in cats)
6) +/- acidosis
*Horses =hypercalcemia & hypophosphatemia

Front 76

What is the specific gravity of urine in animals with chronic real failure?

Back 76

Isosthenuria

Front 77

What is found on urinanlaysis of animals with chronic renal failure?

Back 77

Unremarkable urine sediment

Front 78

What are 3 causes of glomerulopathy?

Back 78

1) Amyloid
2) Chronic antigenic stimulus
3) Immune-mediated

Front 79

What will you see on the urinalysis of a dog with a glomerulopathy? USG?

Back 79

Proteinuria
USG normal or decreased

Front 80

What 3 abnormalities do you see on the blood work of an animal with a glomerulopathy?

Back 80

1) +/- azotemia
2) Hypoalbuminemia
3) Hypercholesteremia in nephrotic syndrome

Front 81

True or false. It's not important to note the route of urine collection for urinalysis.

Back 81

False, important to know for interpretation of results

Front 82

Why is it important to know that urine is a void sample?

Back 82

May contain things that come from the environment, hair, lower urinary tract and genital tract

Front 83

What is the advantage of catheterized urine collection?

Back 83

Decrease contamination, can collect at your convenience

Front 84

What is the disadvantage of collecting a catheterized urine sample?

Back 84

Potential for trauma and hematuria; could contaminate urinary tract; not always easy!

Front 85

What are the advantages of cystocentesis?

Back 85

Usually easier than catheterization, less risk of contamination of urinary tract, urine sample comes directly from the bladder-easier to interpret

Front 86

What are the disadvantages of cystocentesis?

Back 86

May be contaminated w/ blood; potential for trauma

Front 87

You should perform a U/A within ______ of collection or refrigerate in an air tight container.

Back 87

30 minutes

Front 88

U/As should be performed at _______ temperature.

Back 88

Room temperature-let warm if in the fridge

Front 89

What are the 4 components of urinalysis?

Back 89

1) Gross assessment
2) Urine specific gravity
3) Chemical analysis (dipstick)
4) Sediment examination

Front 90

Urine can vary from almost colorless to _____ normally.

Back 90

Dark yellow

Front 91

What does it mean if urine is a dark yellow to brown color?

Back 91

Bilirubinuria

Front 92

What does it mean if urine has a red color?

Back 92

1) erythrocytes
2) Hemoglobin
3) Myoglobin (reddish brown)

Front 93

What animal has normally cloudy urine where as most species are clear turbidity?

Back 93

Horses (crystals and mucus )

Front 94

What does cloudiness of urine indicate (not in horses)?

Back 94

Formed elements e.g. casts, crystals, bacteria

Front 95

What does it mean if urine smells like ammonia? Acetone?

Back 95

May be bacterial splitting of urea
Acetone-ketosis

Front 96

Urine specific gravity is an estimate of _______.

Back 96

Estimation of osmolality

Front 97

When should you use the supernatant of urine to run specific gravity instead of plain urine?

Back 97

When its cloudy

Front 98

Urine chemistries are most often measured using ______.

Back 98

Dipsticks

Front 99

You should store dipsticks properly and protect them from _____ and _____.

Back 99

Light and temperature extremes
*Watch expiration date

Front 100

What causes acidic urine?

Back 100

High protein diet
Anorexia

Front 101

______ tend to have alkaline urine.

Back 101

Herbivores

Front 102

Some UTIs will cause a _______ pH.

Back 102

Higher

Front 103

True or false. Diets and drugs can affect the urine pH.

Back 103

True

Front 104

_______ determines what types of crystals and stones can form.

Back 104

pH

Front 105

Glucosuria happens when the _____ is exceeded.

Back 105

Renal threshold

Front 106

What causes glucosuria?

Back 106

Rarely-if not hyperglycemia-failure of renal tubules to resorb glucose

Front 107

False negatives on glucose in the urine can occur with ________.

Back 107

Ascorbic acid (Vit C)

Front 108

What are 5 causes of a positive urinalysis for ketones?

Back 108

1) Starvation
2) Insulinoma
3) Diabetic ketoacidosis
4) High fat/low carb diets
5) Persistent hypoglycemia

Front 109

Normal dogs can have detectable ______ in their urine especially if the USG is high.

Back 109

Bilirubin (small amounts)

Front 110

Bilirubinuria is always significant in ______.

Back 110

Cats

Front 111

What are 2 causes of bilirubinuria?

Back 111

1) Cholestasis
2) Hemolysis

Front 112

What does a positive for blood on a dipstick mean?

Back 112

RBCs, hemoglobin, or myoglobin

Front 113

What do you need to do if an urinalysis is positive for blood?

Back 113

Need to sort it out by microscopic sediment exam, look at plasma for evidence of intravascular hemolysis, anemia, increased CK etc

Front 114

What are 6 causes of hematuria?

Back 114

1) Infection
2) Inflammation
3) Trauma
4) Calculi
5) Bleeding disorder
6) Neoplasia in urinary tract

Front 115

Normally little protein makes it through the glomerulus and if it does, _________.

Back 115

Most is resorbed by tubules

Front 116

There may be small amounts of proteinuria in normal animals, especially if ________.

Back 116

Urine is concentrated

Front 117

When can false positives for protein in the urine occur with dipsticks?

Back 117

Alkaline urine

Front 118

What are 4 causes of proteinuria?

Back 118

1) Hemorrhage
2) Infection
3) Intravascular hemolysis
4) Renal disease
-Urine sediment has to be evaluated to rule in /out causes

Front 119

What test is used to confirm proteinuria?

Back 119

Sulfosalicylic acid precipitation test
-Add 3-5% SSA to urine sample -look for precipitation

Front 120

When is the urine protein:creatinine ratio used?

Back 120

Quantitative test that's used if no obvious explanation for proteinuria (such as inflammation, hemorrhage, infectino)

Front 121

When do you need to submit to the lab for a urine protein: creatinine ratio?

Back 121

Used if no obvious explanation for proteinuria e.g. inflammation, hemorrhage, infection

Front 122

What does the urine protein: creatinine ratio reflect? What is considered significant protein loss?

Back 122

Amount of protein lost in urine because creatinine excretion is constant during the day
-Ratio>1 considered significant protein loss

Front 123

What are 3 dipstick tests that are not very valuable in veterinary medicine?

Back 123

1) Urobilinogen
2) Nitrites
3) WBCs

Front 124

What can urobilinogen on a dipstick tell you?

Back 124

If absent indicates complete bile duct obstruction but not sensitive

Front 125

When performing a urine sediment examination, formed elements include what 4 things?

Back 125

1) Cells
2) crystals
3) Casts
4) bacteria

Front 126

How do you perform a urine sediment examination?

Back 126

Urine is centrifuged at low speed for 5 minutes
supernatant is poured off to leave .5 ml in tube
-Put a drop on a microscopic slide and add coverslip

Front 127

What do you need to do to the microscope when viewing a urine sediment?

Back 127

Put condenser lens way down

Front 128

How many RBCs are normal in microscopic exam of urine sediment?

Back 128

up to 5 /hpf in normal animal (remember method of collection
-more than that=hematuria

Front 129

What are 2 artifacts seen on microscopic examination of urine sediment?

Back 129

Air bubbles
Lipid droplets (common in cats)

Front 130

How many WBCs is normal on urine sediment? What does it mean if there's more?

Back 130

up to 5 / hpf
-more than that is pyruria

Front 131

What happens when rod shaped bacteria sit in the urine for a while?

Back 131

Can elongate and look like fungal hyphae

Front 132

Where can epithelial cells come from that are in urine sediment?

Back 132

Kidneys, ureters, bladder, urethra, repro tract

Front 133

How do renal cells appear on a microscopic exam of urine sediment?

Back 133

Small and round (from tubules)

Front 134

If you see squamous cells on a urine sediment exam, where could they be from?

Back 134

Urethra, vagina, prepuce or skin

Front 135

What does it mean if there are epithelial cells, renal cells, transitional cell or squamous cells in the urine sediment?

Back 135

Can be normal; suggest irritation or inflammation if present in increased numbers

Front 136

If you see bacteria in a urine sediment, what's your next step?

Back 136

Can be contaminants or pathogens so look for WBCs

Front 137

Fungal elements are almost always from ______.

Back 137

contaminants

Front 138

If you see bacteria in a urine sediment, what's your next step?

Back 138

Can be contaminants or pathogens so look for WBCs

Front 139

What are 2 urinary tract parasites that can be seen in urinary sediment?

Back 139

1) Capillaria plica (most common)
2) Heartworm (rare!)

Front 140

Fungal elements are almost always from ______.

Back 140

contaminants

Front 141

Formation of crystals in the urine depends on what?

Back 141

Concentration of components and solubility at different pH

Front 142

What are 2 urinary tract parasites that can be seen in urinary sediment?

Back 142

1) Capillaria plica (most common)
2) Heartworm (rare!)

Front 143

True or false. The presence of crystals implies stones.

Back 143

False!

Front 144

Formation of crystals in the urine depends on what?

Back 144

Concentration of components and solubility at different pH

Front 145

True or false. The presence of crystals implies stones.

Back 145

False!

Front 146

What crystals are the most common type found in urine of normal dogs?

Back 146

Struvite or magnesium ammonium phosphate

Front 147

____ crystals are normal in horse urine. How do they appear?

Back 147

Calcium carbonate crystals
Two forms-round and dumbbell shaped

Front 148

When are calcium oxalate monohydrate crystals found in urine?

Back 148

Sometimes with ethylene gycol toxicity

Front 149

What does it mean if you find calcium oxalate dihydrate crystals in urine?

Back 149

Nothing, found in normal animals

Front 150

What does it mean if you find ammonium biurate crystals in the urine?

Back 150

Hepatic disease

Front 151

What causes bilirubin crystals to form in the urine?

Back 151

Same causes as bilirubinuria -cholestasis or hemolysis

Front 152

What are casts made of?

Back 152

Mucoprotein secreted by distal tubular cells; formed as cylinders

Front 153

How can you tell that necrosis or inflammation is present by looking at casts?

Back 153

Elements get trapped in the mucoprotein e.g. RBC or WBC casts
-Shed into urine intermittently
-Absence doesn't rule out renal disease

Front 154

What are hyaline casts?

Back 154

Just protein

Front 155

What does a waxy cast indicate?

Back 155

Chronic lesion