SDL: Laboratory tests of renal function Flashcards
What is oliguria and what amount of urine classifies as this?
production of abnormally small amounts of urine
What is anuria and what amount of urine classifies as this?
failure of the kidneys to produce urine
What is polyuria and what amount of urine classifies as this?
production of abnormally large volumes of dilute urine
>3000ml
What does plasma urea measurement show?
quick, simple measurement
sensitive but non specific to illness
What factors influence plasma urea concentration?
liver amino acids
kidney filtration
kidney reabsorption/excretion
When is more that 40% of urea reabsorbed?
rate of tubular flow is slow
tubular flow rate is slow when there is renal hypopeperfusion
When can you get increased plasma urea?
GI bleeds trauma renal hypoperfusion acute/chronic renal disease post-renal obstruction
What should be considered when testing for urea?
input, output and patients fluid volumn
What is the normal range for plasma creatinine?
50-14umol/L
increases in concentration as GFR decreases
not proportional to renal damage
change within individual patient more important than absolute value
What can Plasma creatinine reach in chronic renal disease?
1000 umol/L
What is Glomerular filtration rate (GFR)?
best test to measure your level of kidney function and determine your stage of kidney disease calculated using: blood creatinine test age body size gender
when does tubular secretions of creatinine clearance affected?
increases in chronic renal disease
inhibited by drugs e.g. salicylates
What renal test is most commonly used in current practice?
eGFR
produces stage 1-5 of kidney disease
What would tests show for pre-renal oliguria?
GFR reduced
ADH increased - Concentrated urine
Renal hypoperfusion causes renin secretion - Functioning nephrons increase sodium reabsorption (aldosterone), Urine sodium concentration is low
What can pre-renal oliguria lead to?
Dehydration - sodium / water
Haemorhage
Renal artery damage
Hypotension
