Renal function/integrity (Yr 4) Flashcards
what are the functions of the kidney?
excretion of waste
control of body fluid balance (pressure, electrolytes, acid-base)
production of hormones (erythropoietin, calcitriol, renin)
what is calcitriol?
active form of vitamin D
what is excreted by the nephron?
urea
creatinine
potassium
hydrogen
phosphate
ketones/lactate
what is conserved by the nephrons?
water
amino acids/proteins
glucose
bicarbonate
sodium/chloride
magnesium/calcium
what are the three parts of a urinalysis?
USG
dipstick
sediment
what needs to be measured to determine if the kidneys are working effectively?
glomerular filtration rate
how can glomerular filtration rate be measured accurately in practice?
exogenous creatinine clearance (this is rarely done)
how can GFR be indirectly measured in practice?
urea or creatinine
how will urea and creatinine change if GFR decreases?
will both increase as they aren’t being filtered
how are urea and creatinine differed?
urea is made in the liver from ammonia and can be reabsorbed
creatinine is constantly produced by muscle and not reabsorbed
where is creatinine made?
muscles (constantly produced)
is creatinine or urea a better marker for GFR?
creatinine as it isn’t reabsorbed by the kidney and is less effected by other processes
what can cause increased urea?
decreased GFR
upper GI haemorrhages
recent meals
catabolism (fever, corticosteroids…)
what can cause decreased urea?
severe liver disease or portosystemic shunts
low protein diet
aggressive fluid therapy
PUPD
young animals
what can cause increased creatinine?
decreased GFR
high muscle mass
high dietary protein
what can cause decreased creatinine?
reduced muscle mass
what is the name for increase urea and creatinine in blood?
azotaemia
what are the three causes of azotaemia?
pre-renal
renal
post-renal
what causes pre-renal azotaemia?
dehydration or decreased cardiac output
how can you tell azotaemia is pre-renal?
clinical evidence of dehydration/hypovolaemia
if USG is normal (adequately concentrated)
they should respond to fluid therapy
what is adequate concentration for USG?
dogs - >1.030
cats - >1.035
how can you diagnose if an azotaemia is renal?
variable USG…
can be isosthenuric (1.008-1.012)
USG inadequately concentrated (<1.030 in dogs, <1.035 in cats)
how can post-renal azotaemia be diagnosed?
lack of urine output, full bladder (painful)
usually hyperkalaemic
how much nephron function needs to be lost for renal azotaemia to present?
75%
what is a possible test for GFR that increases when there is less nephron loss (40%) so can detect disease earlier?
SDMA (not perfect… puppies/kittens)
what are the three main electrolyte changes associated with the kidney?
phosphorous
potassium
calcium
what does hyperphosphataemia reflect in animals with high dietary phosphorous content?
decreased GFR
what can cause increased potassium?
fluid compartment shift in acidosis
decreased urinary output (anuria, oliguria, bladder rupture, obstruction)
what can cause increased potassium?
increased urinary loss (CKD)
decreased food intake or GI loss
where is urea made?
liver
what is USG a measure of?
solutes in urine
what is the USG of plasma?
1.010
what is adequately concentrated urine in dogs and cats?
dogs >1.030
cats >1.035
when would a sub-optimally concentrated urine be a cause for concern?
if the animal is dehydrated
if USG is hyposthenuric (lower than 1.010) are the kidneys functioning normally?
yes - nephrons have to be functioning otherwise they would be isothenuric
what is needed to accurately quantify proteinuria?
protein to creatinine ratio (UPCR)
what are the three things that should be checked when you have diagnosed a proteinuria?
location
persistence
magnitude
where can proteinuria be located to?
pre-renal
renal
post-renal
what can cause a pre-renal proteinuria?
fever
systemic inflammation
haemoglobinaemia
myoglobinaemia
what can cause a post-renal proteinuria?
UTI
nephrolithiasis
tumours of urinary tract
is glucose a normal constituent of urine?
no (not normally present)
what is ignored on a dipstick for urine?
nitrite
leucocytes
what are casts?
cylindrical moulds of tubules composed of mucoproteins (plus cells)
where can you localise the problem to if there are casts in the urine?
the actual kidney (tubules)
when should urine be assessed for crystals?
only in fresh urine (older samples can develop crystals)
what are the common crystals seen in urine?
struvite
urate
phosphate
calcium oxalate di/monohydrate
ammonium biurate
cystine
what shape are struvite crystals?
coffin lid
what substance makes struvite crystals?
magnesium ammonium phosphate
what pH urine do struvite crystals form in?
alkaline
what crystals are associated with ethylene glycol toxicosis?
calcium oxalate monohydrate
