Syndrome of inappropriate secretion of antidiuretic hormone

This code signifies a disorder characterized by excessive release of antidiuretic hormone (ADH) from the posterior pituitary gland or an ectopic source, leading to water retention and dilutional hyponatremia. It results in the body holding onto too much water, diluting the sodium in the blood.

Use this code when documentation confirms a diagnosis of SIADH, typically evidenced by hyponatremia (serum sodium <135 mEq/L) with inappropriately concentrated urine, euvolemia or mild hypervolemia, and normal renal and adrenal function. Common causes include malignancies, central nervous system disorders, pulmonary diseases, and certain medications.

• Ensure documentation clearly distinguishes SIADH from other causes of hyponatremia, such as volume depletion or renal failure.
• Always code the underlying cause of SIADH, if known, as the primary diagnosis, with this code as a secondary diagnosis.
• Do not confuse with other endocrine disorders affecting fluid balance, such as diabetes insipidus.