Box 1.

Essential diagnostic criteria for SIAD37

  1. Plasma hypoosmolality (<275 mOsm/kg)

  2. Inappropriate urine concentration (Uosm >100mOsm/kg H20)

  3. Urine sodium >30mmol/L, with normal salt and water intake

  4. Clinical euvolaemia

  5. Exclusion of glucocorticoid deficiency or hypothyroidism (rare)

Supplementary criteria are not included as these are not used routinely in clinical Practice.