In this section
This test is performed on children suspected of having diabetes
insipidus (because of polyuria/polydipsia).
Notify Biochemistry that a Urine Concentration/Water
Deprivation Test will be performed on the next day.
If body weight drops 3% and serum osmolality is > 290 mosm/kg
H2O the test has been performed satisfactorily. If serum
osmolality is less than 290 or body weight has not dropped 3% the
test is unsatisfactory and the urine osmolalities may be
If the test has achieved adequate dehydration (3% weight loss),
urine osmolality >800 mosm/kg indicates normal urine
concentrating capacity. Maximum urine osmolality <250
mosm/kg indicates diabetes insipidus. Maximum urine
osmolality between 250 and 800 mosm/kg indicates either an
unsatisfactory test, partial diabetes insipidus, chronic renal
failure, diuretic administration or severe psychogenic
A positive Urine Concentration Test (ie Failure to concentrate
urine >250 mosm/kg) indicates a diagnosis of Diabetes
Insipidus. Response to DDAVP indicates whether the problem is
due to deficiency of ADH or resistance to ADH (nephrogenic diabetes
DDAVP response can be determined at the end of a Urine
Concentration Test or can be determined on a separate occasion.
Intranasal DDAVP, O.25 ml (25 µg) is given and urine collected
in separate aliquots for 6 hours. The patient may drink ad
lib. Urines are sent for osmolality (if no increase in
osmolality, ADH resistance is present).