Renal Clinical Pathology

Question 1

Glomerular filtration rate (GFR)

Answer 1

the rate fluid moves from the plasma to the glomerular filtrate

Question 2

azotemia

Answer 2

increased non-protein nitrogenous compounds in the blood (urea nitrogen and creatinine)

Question 3

uremia

Answer 3

urinary constituents in blood but more commonly refers to the clinical signs associated with renal failure which are vomiting, diarrhea, coma, convulsions, ammonia odor to breath

Question 4

Isosthenuria

Answer 4

the state in which the urine osmolality is the same as plasma osmolality

Question 5

hyposthenuria

Answer 5

the state in which the urine osmolality is less than isosthenuric values - the urine has been diluted by the kidney

Question 6

renal disease

Answer 6

morphologic, functional, and/or biochemical abnormalities of the kidneys. It is not a specific disease, but rather a group of conditions that cause reversible or irreversible renal lesions. The lesions vary in severity, distribution, and characterization. Not all animals with renal disease have renal failure.

Question 7

renal insufficiency

Answer 7

reduction in renal function due to an underlying renal disease, but not yet resulting in overt azotemia. The ability to concentrate urine is lost. Approximately 2/3 of nephrons are non-functional at this point

Question 8

renal failure

Answer 8

reduction in renal function leading to azotemia due to loss or dysfunction of >75% of the nephrons

Question 9

Normal USG range Cats

Answer 9

1.014 -1.035

Question 10

Normal USG range Dogs

Answer 10

1.014 - 1.030

Question 11

Normal USG range Horses

Answer 11

1.014 -1.025

Question 12

Normal USG range Cattle

Answer 12

1.014 - 1.025

Question 13

how do you interpret water deprivation tests data?

Answer 13

1. withhold water -> urine concentrated = psychogenic polydipsia
2. withhold water -> urine inadequately concentrated -> administer ADH -> urine concentrated-> central diabetes insipidus
3. withhold water -> urine inadequately concentrated -> administer ADH -> urine inadequately concentrated -> nephrogenic diabetes insipidus -> medullary washout (low BUN, NaCl)

Question 14

pre-renal azotemia

Answer 14

increased BUN/ or creatinine
Hypersthenuria
Urine sediment usually quiet

Causes:
**dehydration **
increased protein metabolism/catabolism
decreased plasma oncotic pressure

Question 15

renal azotemia

Answer 15

Increased BUN/or creatinine
isosthenuria or minimally concentrated
urine sediment usually quiet

Cause: any disease causing loss of >75% of the nephrons

hypovolemia (pre-renal) may be contributing to the azotemia

Question 16

post-renal azotemia

Answer 16

increased BUN and/or creatinine

USG is variable

Urine sediment may show hematuria, casts, renal cells depending on lesion location and duration

cause: urinary tract obstruction
clinical signs: oliguria, stranguria, anuria

often have electrolyte abnormalities: decreased Na, Cl and increased K, P

Question 17

know the ability and limitations associated with the use of urea for assessing GFR

Answer 17

NH4 produced in tissues and the intestines are converted to urea in the liver, then urea is excreted in the urine and GI tract
- requires > 75% nephron loss to increase BUN

Question 18

know the ability and limitations associated with the use of creatinine for assessing GFR

Answer 18

product of muscle breakdown that is produced at a relatively constant rate
- requires >75% functional nephron loss to increase crt
- more sensitive than BUN in large animals

Question 19

know the ability and limitations associated with the use of SDMA for assessing GFR

Answer 19

more sensitive for decreased GFR than BUN and creatinine - only needs 25% functional loss

not affected by muscle mass or diet
available for dogs and cats

Question 20

what three solutes are the best at measuring GFR

Answer 20

urea, creatinine, SDMA

Question 21

what are some common disorders that can inhibit renal concentrating ability?

Answer 21

nephrogenic diabetes insipidus
medullary washout
osmotic diuresis

Question 22

common analyte changes with renal failure

Answer 22

Sodium:
- increased with hypovolemia and pure water loss
- decreased with polyuria

Potassium:
- increase with post-renal causes
- decrease in cats, cattle, and occ dogs with CRF

Calcium:
- decreased vitamin D vs decreased urinary excretion
- normal to decreased in dogs and cats
- increased in horses

Hyperphosphatemia (dogs and cats)
- leads to metastatic mineralization where Ca x P >80

Question 23

acute renal failure

Answer 23

• rapid onset: hours to days
• etiologies: nephrotoxin exposure, infectious disease, hemodynamic collapse, ischemia/infarcts, urinary tract obstruction
• prognosis: immediately life-threatening, may be reversible
• urine volume: oliguric to anuric
• urine sediment: variable, may see inflamm cells, RBC’s, bacteria, casts
• proteinuria: +/-
• potassium: normo - to hyperkalemia
• kidney size: +/- enlarged or painful
• anemia: +/-

Question 24

chronic renal failure

Answer 24

• slow onset
• usually idiopathic
• prognosis: progressive and irreversible
• urine volume: polyuric most often
• urine sediment: inactive, may see casts
• proteinuria: +/- neg prognostic indicator
• potassium: normal to hypokalemia
• kidney size: usually small
• anemia: expected, non regenerative due to lack of EPO production