Renal 1 Flashcards
4 renal functions
eliminate metabolic wastes, water and electrolyte balance, acid base regulation, and endocrine (RAA, erythropoietin, vit D)
Calcitriol produced from calcidiol by ________ in proximal renal tubular epithelial cells
alpha-1 hydroxylase
3 processes that control H2O, electrolyte, and waste excretion are
GFR, tubular resorption, tubular secretion
what is the glomerulus? what is the GFR?
glom glom = filtration unit of kidney
glom filtration rate = rate at which blood is filtered through all of glomeruli, and thus measure of overall renal function
what are 2 properties of freely filterable substances
small <3.4 nm and positive or neutral charge
eg. albumin is negatively charged, so albuminuria indicates subclinical disease
glomerular disease will increase or decrease leakiness
increase
renal function: reabsorption occurs in the ________ while secretion occurs in the _________
proximal tubules; distal tubules
renal function: what is tubular disease
retention of metabolic wastes; acid base and electrolyte disturbances; inability to concentrate or dilute urine
what 3 things does renal concentrating ability depend on (kinda 4 things)
renal interstitium (concentration gradient of NaCl and urea is needed for formation of medullary interstitial osmotic gradient), functional tubules, ADH and ADH responsiveness
to dilute urine requires what 2 things
sufficient filtered Na+ and Cl- and active transport in ascending limb
concentrate urine requires what 2 things
ADH and concentration gradient (NaCl and urea)
what does USG assess?
renal concentrating/diluting ability using a refractive index
what is USG range, and what does it depend on
1.001-1.065, depends on hydration status
give adequate renal concentrating ability USG values for dog, cat, cow, horse
> 1.030 Dog, >1.035/40 Cat, >1.025 Cow and horse
what does isosthenuria indicate?
what is the range on USG?
kidney unable to concentrate of dilute urine, classified as renal azotemia (intrinsic renal disease) when azotemia is present.
1.008-1.012
what does hyposthenuria indicate? what is the range on USG?
kidney unable to dilute urine, <1.008
what 2 general types of kidney disease exist? can they be differentiated by bloodwork alone?
acute and chronic.
no, need C/S and hx, duration of signs, etc.
exceptions exist, eg. anemia of inflammatory renal disease = CKD
if you have pre-renal azotemia, what is USG? what does it mean?
USG > 1.030, so adequate concentrating ability, but there is impaired renal blood flow or decreased perfusion (decreased blood volume) and if left untreated can lead to renal hypoxia and renal azotemia
with post-renal azotemia, what is the USG value? what does it mean?
USG variable
distal to nephron obstruction: increased intracapsular hydrostatic pressure/afferent arteriolar constriction that decreases GFR/decreases delivery of waste
what does uremia refer to
clinical signs associated with renal failure: V/D, weakness, ammonia smell breath
what is the major nitrogenous waste product from mammals? how is is synthesized and excreted?
BUN/urea.
synthesized in liver from CO2 and ammonia via the urea cycle
excreted almost exclusively in URINE
EXCEPT in cattle and horses it is excreted in GI system where it is degraded to NH4+ by enteric bacteria with urease, in rumen and cecum, respectively, then passively absorbed into portal blood as AA or excreted into feces
BUN/urea is readily filtered by what? is this passive or active?
glomerulus
passive diffusion to excrete into urine (or in cattle and horses, into GIT then passive diffusion into portal blood as AA or excreted into feces)
3 conditions you would see INCREASED BUN/urea
decreased GFR (any reason), increased protein digestion (more in diet or hemorrhage into GIT), protein catabolism due to fever
3 conditions you would see DECREASED BUN/urea
decreased production (liver failure or PSS), decreased protein diet/malnutrition, increased excretion, urea cycle enzyme deficiencies, but rare
creatinine is produced where (at a constant rate, as a result of normal muscle metabolism)
skeletal muscle. not the same as CK which is a leakage enzyme in cytoplasm of myocytes
which enzyme is produced in skeletal muscle at a constant rate as a result of NORMAL muscle metabolism and not reabsorbed (is excreted unchanged by renal tubules or collecting ducts)? which is a LEAKAGE enzyme in cytoplasm of myocytes (not a marker of kidney disease, but a marker of either muscle damage or liver disease)
creatinine; creatine kinase
what is azotemia
increased BUN and creatinine. markers of kidney disease
***renal failure (aka renal insufficiency or preferred term kidney disease/injury) occurs when ____% of functional renal mass is lost and ______ develops
66-75%; azotemia
acute vs chronic kidney disease or injury: which is reversible?
acute is potentially reversible, chronically irreversible. again, can’t be diagnosed with lab tests alone definitively because there is considerable overlap
assessing kidney disease with creatinine and BUN: what should you consider with increased BUN?
other causes of increased BUN are:
- intestinal hemorrhage
- increased protein catabolism (generates increased NH4+ this increased BUN production by hepatocytes) (creatinine will be normal and BUN increase will be mild)
assessing kidney disease with creatinine and BUN: what should you consider with creatinine?
consider muscle mass
assessing kidney disease with creatinine and BUN: what should you consider with creatinine?
consider muscle mass
compare serum creatine and serum SDMA: which increases at earlier % function loss? which is more specific? which is more sensitive? which is affected by
both are specific (serum creatinine 100%, serum SDMA 91%)
serum creatinine: increase at 75% function loss, NOT sensitive (17%), decreases with age and hyperthyroidism in cats, variable reference ranges
serum SDMA: increases at only 40% loss, 100% sensitive, not affected by age, muscle mass, or hyperthyroidism, ONE reference range
***can you interpret azotemia properly without USG?
no
three components of urinalysis are
physical, chemical, microscopic
cylinduria (casts in urine) can be seen with what condition
tubular disease
crystalluria can be potential cause of what disease, (but is not a reliable indicator for presence of uroliths/nephroliths)
kidney disease
glucosuria in a normoglycemic patient is indicative of what disease
tubular disease
is proteinuria in dilute urine a cause for concern that should be investigated
always!
(in some healthy dogs in dilute urine can be microalbuminura (small amounts albumin))
***hypoalbuminemia in blood is most often associated with what kind of proteinuria?
renal proteinuria
what are 3 types of proteinuria? (kinda 4, one please give the two subtypes)
pre-renal (overflox proteinuria) = more small blood proteins get filtered through the glom glom
renal proteinuria: glomerular = damage to the glom glom so decreased selective permeability and passage of larger proteins
renal proteinuria: tubular = damage to tubules, so smaller proteins that should be resorbed are not
post-renal (hemorrhagic and inflammatory proteinuria) = hemorrhage or inflammation in LUT, eg. UTI
what is UPC ratio? what does it help to conform?
evaluates loss of protein relative to creatine (since creatinine filtration is relatively constant in healthy animals)
helps confirm a renal proteinuria
tell me the normal UPC ratio in dogs? what is abnormal (hint: think what the UPC ratio is used to help confirm)
normal is <0.5
remember they help to confirm a renal proteinuria
- tubular proteinuria will be >0.4 (if azotemic) or 1-2 (if not azotemic)
- glomerular proteinuria >2.0 (more dramatic)
