Severe Transient Central Diabetes Insipidus After Pituitary Adenoma Removal With Peak Urine Output of 33.5 L in 24 h

Background: Postoperative central diabetes insipidus (CDI) is a well-documented but often transient complication following transsphenoidal surgery (TSS) for pituitary adenomas. CDI is characterized by excessive urine output due to impaired antidiuretic hormone (ADH) secretion following damage to the neurohypophyseal stalk or hypothalamus. While most cases resolve within a few days, severe cases with extremely high urine output are rare. This case is notable due to an exceptionally high urine output of 33.5 L in a single day, far exceeding typical postoperative presentations and highlighting the need for vigilant postoperative monitoring. Case Presentation: A 47-year-old female with hypertension and hypothyroidism underwent endoscopic endonasal TSS at Tribhuvan University Teaching Hospital (TUTH) for a pituitary macroadenoma compressing the optic chiasm. Within hours postoperatively, she developed significant polyuria exceeding 1000 mL/h, with urine osmolality of 213.3 mOsm/kg and hypernatremia (serum sodium 149 mmol/L), consistent with CDI. Urine output increased to 30.8 L on postoperative day 2 and peaked at 33.5 L on day 3, requiring aggressive fluid replacement and desmopressin therapy. Despite escalating doses of desmopressin, polyuria persisted before gradually resolving by postoperative day 5. Careful monitoring of electrolytes and stepwise adjustment of desmopressin led to stabilization, confirming transient rather than permanent CDI. Conclusion: This case highlights that postoperative CDI can present with extreme polyuria and rapid shifts in sodium and osmolality, making early recognition essential. It reinforces that individualized desmopressin titration and close fluid-electrolyte monitoring are critical to prevent complications and support full recovery, especially when urine output reaches unusually high levels.