measurement of renal function Flashcards
why would you measure renal function.
identification of renal impairment
modifying drug dosage (which are cleared by kidneys)
patients at risk of developing renal failure
extremes of age
polypharmacy
specific disease states
long term analgesia (NSAIDS nephrotoxic)
transplant patients (rejection, anti rejection drugs)
drug therapy (nephrotoxic - anti biotic/cancer/hiv)
imaging procedures
how does GFR dec with age
Matures at 4 years
dec by 0.4-1.2mL/min per year after 40
diseases affecting GFR
hypertension diabetes chronic HF rheumatoid arthritis renal disease recurrent UTIs
how can renal function be monitored
clinical condition (clinical assessment, bedside data) modern imaging techniques (macroscopic view of renal flow, filtration and excretory functionalists) biochemical data(renal clearance of substances, evaluate ability to handle water and solutes)
what happens if fluid balance affected
oedema - breathlessness
what happens if electrolytes regulation (K, Na, Ca, PO4) are affected
abnormal ECG (absent P waves, broad QRS, peaked T) absent symptoms
what happens if EPO production is affected
pallor - fatigue
what happens with vit D is affected
osteomalacia - bone pain
what happens if excretion is effected
raised blood creatine and urea conc - pruritis, nausea and vomitting
what happens if acid base balance is affected
low blood ph and bicarbonate levels - deep and rapid respiration
what us bedside clinical data
weight chart
fluid balance chart
degree of oedema
results of urine dipstick testing (urinalysis for protein, blood, glucose)
what is renography
gamma camera planar scintigraphy
positron emission tomography (PET)
single photon emission computerised tomography (SPECT)
what is biochemical data used for
identifying renal impairment
what is biochemical data
blood (plasma or serum) markers of renal function
plasma or serum creatinine
plasma or serum urea or blood urea nitrogen
what is creatinine
breakdown production of creatinine phosphate in muscle
generally produced at constant rate
filtered at glomerulus with some secretion into PT
normal range 40-120 umol/L
what increases plasma creatinine
large muscle mass, diet drugs with interfere with analysis drugs that inhibit tubular secretion ketoacidosis ethnicity (higher if black)
what decreases plasma creatinine
reduced muscle mass
cachexia/starvation
immobility
pregnancy (due to inc plasma vol of mother)
severe liver disease (liver source of creatinine)
how does plasma creatinine indicate renal failure extent
normal 100 (40-120) normal function up to 150 mildly reduced 150-300 mod 300-500 sev 500-700 very sev >700
what is urea
liver produces it in urea cycle as waste product of protein digestion
filtered at glomerulus, sec and abs in tubule
described as BUN
normal 2.5-7.5 mmol/L
>20 sev failure
what increases urea
high protein diet hyercatabolic conditions (eg sev infection, burns) GI bleeding muscle injury drugs tetracycline hypovolaemia
what decreases urea
malnutrition
liver disease
sickle cell anaemia
SIADH
what is biochemical data useful for indicating
identifying renal impairment
evaluation of ability of kidneys to handle water and solutes
modifying dodges pf drugs which are cleared by kidneys
some methods measure renal clearance of substances
what would an ideal marker of renal function be
a naturally occurring molecule
not metabolised
only excreted in kidney
filtered but not secreted or reabsorbed by the kidney
