Post from Nickson on Life in the Fast Lane
USES
Oliguria
- UNa+ low (<10mmol/L) – extravascular volume depletion
- UNa+ high (>20) – tubular damage
Hyponatraemia
- UNa+ low (<10) – extra-renal losses
- UNa+ high (>20) – renal salt losing states, SIADH, diuretic therapy
- Fractional excretion of Na+ = 100 x UNa+ x PCr / PNa+ x UCr
-> < 1% implies pre-renal cause, limited by Na+ intake and diuretics therapy
Hypokalaemia
- UK+ high (>20) – renal loss of K+
- UK+ low (<20) – extrarenal loss of K+
Normal Anion Gap Acidosis
- UCl- can be used
- UCl- low (<10) – RTA from impaired urinary acidification (decreased ammonium excretion)
-> also present = positive urinary anion gap and an inappropriately high pH (>6) - if acidosis is due to an extra-renal loss of bicarbonate, in the absence of renal failure the kidneys will excrete ammonium and chloride
-> negative urinary anion gap (UCl > Na + K)
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Excellent Powerpoint
Oliguria by Raimund Pichler M.D
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