Isolated syndrome of inappropriate antidiuresis (SIAD) after Transphenoidal surgery of a non-functioning pituitary adenoma: clinical case report.

Introduction: Disorders of water balance, including arginine vasopressin deficiency (AVP-D) and syndrome of inappropriate antidiuresis (SIAD), are common postoperative complications following pituitary surgery. While AVP-D typically occurs as an isolated condition, SIAD may also present independently.

Clinical case: We describe the case of a patient with a non-functioning pituitary adenoma who underwent transsphenoidal surgery. On postoperative day 7, she developed isolated SIAD, characterized by a plasma sodium level of 113 mmol/L, normovolemia, urine osmolality of 364 mOsm/kg, and urine sodium concentration of 50 mmol/L. A daily fluid restriction of 800 mL resulted in the resolution of hyponatremia within 48 h.

Conclusions: Water balance disorders following pituitary surgery are often unpredictable. This case highlighs the importance of close postoperative clinical and biochemical monitoring. Vigilance is essential, even in the absence of AVP-D, to ensure early detection and management of potentially severe complications such as SIAD.