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Why do diuretics cause increase in serum creatinine?

Discussion in 'Step I' started by LuckiestOne, Jul 23, 2012.

  1. LuckiestOne

    LuckiestOne 2+ Year Member

    Jul 14, 2012
    Probably a very easy question but why do diuretics cause serum creatinine to go up? Thanks in advance.
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  3. Phloston

    Phloston Physician Lifetime Donor Classifieds Approved 5+ Year Member

    Jan 17, 2012
    Osaka, Japan
    If I had to reason through it, it would be that creatinine levels are inversely related to filtration at the glomerulus, so the only way your creatinine is going to go up is if you have decreased GFR. With diuretic-use, plasma volume and serum sodium levels both decrease, so the general compensatory measure would be constriction of the efferent arteriole in order to preserve GFR. However, GFR is not actually increasing. The filtered fraction is merely increasing, which is because renal plasma flow (RPF) is decreasing. So if less plasma passes the glomerulus per unit time, serum creatinine must increase.

    That's just my guess.
  4. Belleza156

    Belleza156 7+ Year Member

    Jan 21, 2009
    Which diuretic causes increase in creatinine? Are you sure you mean diuretics or are you talking about ACE inhibitors which increase serum creatinine by 30% the first 3-5 days which then stabilizes after 2-3 weeks.

    The only connection I know of with increased creatinine due to diuretic use is in nephrogeneic diabetes insipidus, for some reason thiazides have a paradoxic antidiuretic effect on them. That's why the paradox is an extreme diuresis is treated with a diuretic. Thiazide diuretics will decrease distal convoluted tubule reabsorption of sodium and water, thereby causing diuresis. This decreases plasma volume, thus lowering GFR and enhancing the absorption of sodium and water in the proximal nephron. Less fluid reaches the distal nephron, so overall fluid conservation is obtained.

    Is that what you were referring to? If not, sorry I don't know but I would appreciate if someone would answer this.
  5. OveractiveBrain

    OveractiveBrain Banned 2+ Year Member

    Jun 15, 2009
    Dirty Dirt
    Phloston has it.

    Its simpler in clinical medicine. Overdiuresis causes volume depletion. Volume depletion means RAS activation and vasoconstriction. GFR falls, Cr clearence drops.

    Its called pre-renal azotemia (increase in both the BUN and Cr) for a pre-renal (perfusion) cause. One is simply reduced circulating volume.

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