This patient has true hypo-osmolal hyponatraemia due
to water excess. If he is overdrinking fluid and fully
complying with his DDAVP therapy, you would expect him
to have hypo-osmolal hyponatraemia but with
inappropriately high urine osmolality, which is
clearly not the case as his urine osmolality is only
124 mmol/kg. There are two explanations for this
anomaly, either he is overdrinking fluid and is
partially complying with DDAVP which meant that his
kidney has the chance to clear excess water when he
misses the DDAVP dose. The second less likely
explanation is that the urinary osmolality was
analytically incorrect.
regards.
--- margaret egan <[log in to unmask]> wrote: > >Date: Thu,
07 Sep 2000 17:10:29 +0100
> >To: [log in to unmask]
> >From: margaret egan <[log in to unmask]>
> >Subject: conflicting results
> >
> >Dear colleagues,
> >A 49 year old man with cranial diabetes insipidus
> and suspected high
> alcohol intake presented to outpatients with the
> following results -
> >Na 126mmol/l(135 - 145)
> >K 4.0mmol/L (3.5 -5.0)
> >Urea 1.8mmol/L (3.0 - 7.0)
> >Creat 83umol/L (50 - 125)
> >Se Osm - 260mmol/kg
> >U Osm - 124mmol/kg
> >Liver profile, corrected Ca and glucose were
> normal.
> >DDAVP dose was 1 spray eight hourly.
> >Patient was asymptomatic.
> >Any comments?
> >
> >Regards
> >Margaret
>
=====
Dr. M A Al-Jubouri
Consultant Chemical Pathologist
Whiston Hospital
Prescot
Merseyside L35 5DR
UK
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