Case Report
A 27-Month-Old Boy with Polyuria and Polydipsia
Table 2
Interpretation of serum and urine osmolality in the differential diagnosis of polyuria and polydipsia after the water deprivation test.
| | Serum osmolality (mOsm/kg) | Urine osmolality after deprivation (mOsm/kg) | Urine osmolality after DDAVP (mOsm/kg) | Plasma AVP level | Diagnosis |
| | >300 | <300 | >750 | <2 | Central DI | | >300 | <300 | <300 | >5 | Nephrogenic DI | | <290 | >750 | >750 | 2–5 | Primary polydipsia | | >290 | 300–750 | <750 | Variable | Partial DI or primary polydipsia |
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DDAVP, desmopressin; AVP, arginine vasopressin (pg/mL); DI, diabetes insipidus.
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