| Essential criteria |
| Decreased effective osmolality (serum osmolality of <275 mOsm/kg) |
| Urine osmolality of >100 mOsm/kg at some level of serum hypoosmolality |
| Clinical euvolemia, as defined by the absence of signs of volume depletion |
| Elevated urine sodium concentration of >30 mmol/L with normal dietary salt and water intake |
| Absence of other potential causes of euvolemic hypoosmolality: severe hypothyroidism, adrenal insufficiency |
| Normal renal function and absence of diuretic intake (especially thiazide diuretics) |
| Supplemental criteria |
| Serum uric acid, <4 mg/dL |
| Serum urea, <21.6 mg/dL |
| Failure to correct hyponatremia after 0.9% saline infusion |
| Correction of hyponatremia through fluid restriction |
| Fractional sodium excretion, >0.5% |
| Fractional urea excretion, >55% |
| Fractional uric acid excretion, > 2% |
