32.5 Lab tests of renal function Flashcards
What are the functions of the kidney? (3)
Regulation of water, homeostasis and acid-base.
Excretion of urea and uric acid.
Endocrine: renin, erythropoietin, 1,25-dihydroxycholecalciferol.
Which laboratory tests measure renal function? (10).
Glomerular filtration rate.
Plasma creatinine and creatinine clearance.
Plasma urea.
Urine volume, urea, sodium, protein, glucose.
Haematuria.
What is the urine volume in oliguria?
Less than 400ml/24hr.
What is the urine volume in anuria?
Less than 100ml/24hr.
What is the urine volume in polyuria?
More than 3000ml/24hr
Where is urea excreted?
How much is reabsorbed and where?
Glomerulus.
40% in the renal tubules.
What are the common causes of increased plasma urea? (5)
Acute/chronic renal impairment. Post renal obstruction. Renal hypo-perfusion. GI bleed. Trauma.
How is creatinine clearance calculated?
(urine creatinine conc x urine volume) / plasma creatinine conc
What are the common causes of pre-renal oliguria? (4)
Haemorrhage.
Dehydration.
Renal artery damage.
Hypotension.
What changes to lab results are seen in pre-renal oliguria? (3)
GFR reduced.
ADH increased.
Low sodium in urine.
What changes to the lab results are seen in renal oliguria? (4)
GFR reduced/normal.
Weak urine/low volume.
Raised renin secretion - hypertension.
High sodium in urine.
When does plasma creatinine increase?
When is it useful?
When GFR decreases.
Change within a patient over time. Predicts need for intervention in end stage renal failure. Not proportional to renal damage.
Which drugs decrease tubular secretion of creatinine? (2)
Salicylate.
Cimetidine.
What does clearance of [99Tc]-Sn-DTPA measure?
Glomerular filtration rate.
What are the GFR values for: Normal kidney function Mildly reduced, Moderately reduced Severely reduced End stage kidney failure?
90+ 60-89 30-45 15-29 Less than 15/on dialysis.
