The differential diagnosis of hypernatraemia in children, with ...

The Diagnosis of Salt Poisoning Leading to Hypematraemia in Children – September 2009
6. Tests and investigations
6.1 What key tests will help distinguish excess sodium intake from
water depletion?
“The distinction between accidental and non-accidental salt poisoning cannot be made on
clinical or physiological grounds, since the end result of both is the same. Only a meticulous
evaluation of the history and the attendant circumstances of the case can resolve this… The
two conditions that should be distinguishable on clinical and physiological grounds are
hypernatraemic dehydration and salt overload (however induced).” 27
There are several recommendations in earlier sections relating to the initial investigations
to be undertaken in children presenting with hypernatraemia where the cause is not certain.
The section from which each is copied is included in brackets:
Evidence statement
A sample of gastric contents for analysis of sodium content should be obtained as
soon as possible after admission in all children presenting with hypernatraemia of
uncertain cause [Grade D]. (section 4.4)
Evidence statement
Careful measurement of weight at the time of admission and before restoration of
full hydration provides a reliable estimate of the degree of dehydration [Grade B].
This should be undertaken if possible in children presenting with hypernatraemia of
uncertain cause [Grade D]. (section 4.4)
Evidence statement
A urine sample for calculation of fractional urinary sodium excretion (for which plasma
and urine sodium and creatinine measurements are required) in the presence of normal
renal function should help to ascertain whether the hypernatraemia is secondary to
excessive sodium ingestion [Grade D]. Regular urine samples for fractional urinary
sodium excretion are recommended in children presenting with hypernatraemia of
uncertain cause [Grade D]. (section 4.4)
Evidence statement
In a child with hypernatraemia a urine osmolality can assist in excluding diabetes
insipidus [Grade D]. (section 4.1)
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