Renal Clinical Pathology Flashcards
Glomerular filtration rate (GFR)
the rate fluid moves from the plasma to the glomerular filtrate
azotemia
increased non-protein nitrogenous compounds in the blood (urea nitrogen and creatinine)
uremia
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
Isosthenuria
the state in which the urine osmolality is the same as plasma osmolality
hyposthenuria
the state in which the urine osmolality is less than isosthenuric values - the urine has been diluted by the kidney
renal disease
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.
renal insufficiency
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
renal failure
reduction in renal function leading to azotemia due to loss or dysfunction of >75% of the nephrons
Normal USG range Cats
1.014 -1.035
Normal USG range Dogs
1.014 - 1.030
Normal USG range Horses
1.014 -1.025
Normal USG range Cattle
1.014 - 1.025
how do you interpret water deprivation tests data?
- withhold water -> urine concentrated = psychogenic polydipsia
- withhold water -> urine inadequately concentrated -> administer ADH -> urine concentrated-> central diabetes insipidus
- withhold water -> urine inadequately concentrated -> administer ADH -> urine inadequately concentrated -> nephrogenic diabetes insipidus -> medullary washout (low BUN, NaCl)
pre-renal azotemia
increased BUN/ or creatinine
Hypersthenuria
Urine sediment usually quiet
Causes:
**dehydration **
increased protein metabolism/catabolism
decreased plasma oncotic pressure
renal azotemia
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
post-renal azotemia
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
know the ability and limitations associated with the use of urea for assessing GFR
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
know the ability and limitations associated with the use of creatinine for assessing GFR
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
know the ability and limitations associated with the use of SDMA for assessing GFR
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
what three solutes are the best at measuring GFR
urea, creatinine, SDMA
what are some common disorders that can inhibit renal concentrating ability?
nephrogenic diabetes insipidus
medullary washout
osmotic diuresis
common analyte changes with renal failure
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
acute renal failure
- 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: +/-
chronic renal failure
- 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
