list some functions of the kidney
- eliminate metabolic waste
- water and electrolyte balance
- acid base regulation
- endocrine (aldosterone, erythropoietin, vitamin D/calcitriol)
what are the 3 processes that control H2O, electrolyte, and water excretion in the kidney?
- glomerular filtration
- tubular resorption
- tubular secretion
what is glomerular filtration rate?
the rate at which blood is filtered through all of the gloermuli and thus the measure of the overall renal function
what are some of the freely filterable substances that make it through the glomerulus?
- small things less than 3.4nm
- positively or neutrally charged things (basement membrane is neg charged)
reabsorption happens in the ______ and secretion happens in the _____
proximal tubules
distal tubules
tubular disease will cause what 3 things?
- retention of metabolic wastes
- acid base/electrolyte disturbances
- inability to concentrate/dilute urine
glomerular disease results in
leakiness
renal concentrating ability rewuires what 3 things?
- renal interstisium (to create necessary concentration gradients)
- functional tubules
- ADH as well as ADH responsiveness
what is required to concentrate vs dilute the urine?
concentrate: ADH and a concentration gradient
dilute: sufficient filtered Na and Cl and active transport in ascending limb
what is the normal range for a USG?
1.001-1.065
what are the USGs for:
- adequate renal concentrating ability
- isosthenuria (unable to dilute or concentrate)
- hyposthenuria (kidney cannot dilute)
adequate: more than 1.030/1.035/1.025
isosthenuria: 1.008-1.012
hyposthenuria: less than 1.008
true or false: you can tell acute kidney disease from chronic kidney disease on bloodwork alone
false! you need clinical signs and history and other lab findings!!!
what are the two main markers of kidney/renal disease?
BUN and creatinine
where does BUN come from? why is it in urine?
BUN/urea is a nitrogenous waste product made in the liver from CO2 and ammonia via the urea cycle and is excreted exclusively in urine, and is filtered by the glomerulus
increased blood urea concentrations are seen with:
- decreased GFR
- increased protein digestion
- protein catabolism/fever
a decrease in blood urea concentrations are seen with:
- decreased production (liver failure or PSS)
- decreased protein diet/malnutrition
- increased excretion (polyuria)
- urea cycle enzymes deficiencies SUPER RARE
what is creatinine and why is it a renal marker?
it is produced in skeletal muscle at a constant rate and is a normal result of muscle metabolism, and it is excreted by the kidney (not the same as creatine kinase)
what are the 3 causes of azotemia with the respective USG values?
- pre renal: impaired renal blood flow or decreased perfusion possibly due to decreased blood volume. USG>1.030
- renal: intrinsic renal disease. USG 1.008-1.012
- post renal: urinary tract obstruction, diagnosed heavily on clinical signs and history, etc, not USG
what is uremia?
refers to clinical signs associated with renal failure like vomiting, diarrhea, weakness, diarrhea, weakness, ammonia breath, etc
renal failure occurs when _____% of functional renal mass is lost and azotemia develops
66-75
what should you take into account when interpreting creatinine values?
muscle mass
true or false: some healthy dogs can have small amounts of albumin in urine
true, can have trace to 1+ in concentrated urine, BUT presence in dilute urine is ALWAYS a concern and should be investigated
what are the 3 types of proteinuria?
- prerenal: increased proteins in the blood going to be filtered thru glomerulus
- renal: glomerular damage and decreased permeability, allows protein to pass through
- post renal: hemorrhage or inflammation in he lower urinary tract like with a UTI
hypoalbuminemia is most often associated with what kind of proteinuria?
renal proteinuria
