Clinical Pathology Of Urinary System

Question 1

Functions of kidney

Answer 1

• Urine production - elimination of metabolic wastes
• Acid-base regulation
• Conservation of water
• Maintenance of normal extracellular potassium concentration
• Endocrine functions
– Erythropoietin
– Renin
– Vitamin D

Question 2

3 major processes control renal excretion of H2O and solutes

Answer 2

• Glomerular filtration
– Filtration of a substance depends on molecular size and electrical charge (e.g albumin)
• Tubular resorption
• Tubular secretion

Question 3

Consequences of impaired renal function

Answer 3

• retention of metabolites that are normally removed by healthy kidneys
• indices of diminished renal function
– plasma or serum concentrations of urea and
creatinine to get idea of kidney function
• Elevated urea and/or creatinine described as AZOTEMIA
• Impaired urine concentrating ability

Question 4

Azotemia

Answer 4

Elevated urea and/or creatinine

Question 5

What is used to assess renal function

Answer 5

Urinalysis- a dipstick that measures protein, blood, glucose, ketones, pH of urine

Question 6

Ways to collect urine

Answer 6

• Voided / free catch
• Catheter
• cystocentesis

Question 7

Urine specific gravity (USG)
-what is it
-what is used to give an index of specific gravity
-large amounts of what will increase USG?

Answer 7

• ratio of a solutions weight to the weight of an equal volume of distilled water
• Refractive index is used to give an estimate of USG
-large amounts of glucose or albumin

Question 8

Hyposthenuria
-meaning

Answer 8

• urine osmolality < isosthenuric values
• diluted urine
• S.G. 1.001 – 1.007

Question 9

Isosthenuria
-meaning
-specific gravity

Answer 9

Specific gravity is 1.008 – 1.012

urine osmolality = plasma osmolality

Question 10

Hypersthenuria
-meaning

Answer 10

• excretion of highly concentrated urine (rarely used term)

Question 11

Regulation of body water
-in healthy animals
-maximal urine dilution S.G in domestic animals;

Answer 11

Healthy animals with normal or adequate renal function can excrete urine with a broad USG range depending on what the kidneys are challenged to do

Maximal urine dilution in domestic species near 1.001

Question 12

Maximal urine conc of
Cat
Dog
Horses/cattle

Answer 12

Cat
>1.080
Dog
>1.060
Horses/cattle
>1.050

Question 13

Best predictor of urine function;

Answer 13

GFR

Question 14

Ideal solute for measuring GFR has what features

Answer 14

• Not be protein bound
• Pass freely through filtration barrier
• Neither be secreted nor resorbed by tubules • Various substances available
• But Expensive

Question 15

Another protein used to measure kidney function and it’s features

Answer 15

CREATININE:
-Protein we can measure in blood
-product of creatine degradation in muscles
• Passes freely through glomerular filtration barrier
• Not resorbed by the tubules
• Rate of production depends on muscle bulk and turnover

Question 16

Another measurement of kidney function; urea

Answer 16

Synthesis occurs in hepatocytes via urea cycle
• Method of excreting excess ammonium
• Kidney excretes most

• Not reliable in cattle
• Urea enters the rumen and Used for AA production

Question 17

Increased creatinine is seen with…

Answer 17

– Decreased urinary excretion, which is seen with;
• Dehydration
• Renal dysfunction
• Outflow obstruction

– High muscle mass
• greyhounds
• bulls

Question 18

Causes for increased urea
nonrenal causes for ^ urea

Answer 18

– Decreased urinary excretion
• Dehydration, hypovolaemia
• Renal dysfunction
• Urinary outflow obstruction

– Nonrenal causes
• High protein diet
• Increased muscle breakdown
• GI bleeding

Question 19

Azotemia vs Uraemia

Answer 19

• Increased non-protein nitrogenous compounds in the blood (we measure elevated urea and creatinine)

• Clinical syndrome reflecting renal failure
– Vomiting, diarrhoea, breath that smells of ammonia

Question 20

Classification of azotemia
-3 different types

Answer 20

• Prerenal- problems occuring before reaching kidney
• Renal- problems within kidney
• Post renal- problem further down urinary tract

Question 21

True or false more than one type of azotemia may occur at once

Answer 21

True

Question 22

Symptoms of prerenal azotemia
-accompanying USG in
Dog
Cat
Horses/cattle

Answer 22

• Dehydration
• Hypovolaemia
• Decreased cardiac output

– Dog >1.030
– Cat >1.035
– Horses/cattle >1.025

Question 23

Renal azotemia
-what is it
-causes
-accompanying USG

Answer 23

Any renal disease with enough glomerular damage to cause a major decrease in GFR

• Loss of 65-75% of nephron functional capacity —> decreased GFR

• Inadequate renal excretion of urea and crt
• Accompanying USG 1.008-1.012 Isosthenuria

Question 24

Post renal azotemia
Caused by…

Answer 24

• The initiating cause of abnormal urea and crt is distal to the nephron

• caused by Urinary tract obstruction
– Release of vasoactive substances
– Glomerular arteriole constriction
– decreased RPF and GFR
– Transient intracapsular hydrostatic pressure – Less ultrafiltrate formed

• Urine leakage into abdomen
– Passive absorption into plasma from peritoneum

• May be anuric

Question 25

What do kidneys do when a patient is dehydrated

Answer 25

Kidneys want to conserve water so produce highly concentrated urine- USG will be highly concentrated

Question 26

What does SDMA stand for
-what is it
-released during what
-useful for…

Answer 26

Symmetric Dimethylarginine

• Small molecule formed by methylation of arginine
• Released during protein degradation
• Useful for early identification and monitoring of chronic kidney disease (dogs/cats)
• Limited availability - Idexx

Question 27

Inorganic phosphate

Answer 27

• Skeletal mineral
• Important intracellular ion
– Enzyme cofactor, phosphorylation reactions

• Calciumandphosphorushomeostasisare
interdependent (see renal secondary hyperparathyroidism)

Question 28

• Markedly decreased GFR in renal failure does what to renal excretion of phosphate

Answer 28

• Markedly decreased GFR in renal failure decreases renal excretion of phosphate—> leads to hyperphosphataemia

Question 29

Calcium
-type of mineral
-functions
-renal failure causes…

Answer 29

• Skeletal mineral
– Muscular contraction, blood clotting, enzyme
function
• Renal failure – may see normo-, hypo- or hypercalcaemia in cats and dogs
• Hypercalcaemia of paraneoplastic syndrome

Question 30

Rubber jaw

-cause by

Answer 30

Minerals removed from bone so bone becomes soft

Question 31

Potassium
-main route of excretion is through…

Answer 31

• Kidney is main route of excretion of excess Potassium from the body
• Hyperkalaemia
– Anuria or oliguria (e.g. ARF)
• Decreased flow of tubular fluid in nephron
– Reduced renal blood
flow

Question 32

Hyperkalaemia and hypokalaemia

Answer 32

Higher than normal potassium levels in the blood.
Lower than normal

Question 33

Albumin

Question 34

Nephrotic syndrome

Question 35

Proteinuria
-how to measure it
-possible causes

Answer 35

Using “stix”
– Sensitive to albumin
– Alkaline urine may give false positive (herbivores)

Haemorrhage, Leucocytes (inflammation), renal disease

Question 36

Urine protein:creatinine ratio

Answer 36

• More accurate measurement of urine protein

Take a blood sample and look at ratio of the two
• <0.2 normal, 0.2-0.5 (dog) and 0.2-0.4 (cat) equivocal, >than this abnormal

• Consider sediment contents before interpretation
– Active sediment e.g. haemorrhage, inflammation make P:C ratio unreliable

Question 37

Renal failure

Answer 37

Decreased GFR (but this may be caused by other things so bear in mind)

• Pre-renal, renal, post-renal
• Acute vs chronic
With renal failure you Must lose significant portion of the kidney before seeing clinical effects