TRIPHASIC PHASE OF CENTRAL DIABETES INSIPIDUS (DI) POST TRANSPHENOIDAL SURGERY

A NORTHERN REGION GOVERNMENT HOSPITAL EXPERIENCE

Abstract

INTRODUCTION/BACKGROUND
The transsphenoidal pituitary surgery approach is a potential cause of central diabetes insipidus (DI) due to its impact on the pituitary stalk. Triphasic DI is a rare manifestation of central DI. In the initial phase, patients experience polyuria secondary to axonal shock or injury of vasopressinsecreting neurons in the hypothalamus. In the second phase, there is transient inappropriate antidiuretic hormone secretion (SIADH) due to vasopressin leakage from the damaged posterior pituitary tissues. The third phase ensues if >80% of vasopressin-secreting neurons are destroyed.

CASE
A 44-year-old Malay female presented with sudden slurring of speech, numbness of the right upper limb and headaches. Her cranial CT and MRI showed pituitary macroadenoma (1.1 x 1.5 x 1.1 cm). Pituitary hormone profile was normal. Ten months later, she developed bitemporal hemianopsia with a repeated cranial MRI showing unchanged size of the sellar lesion. Eventually, she underwent transsphenoidal surgery and tumour excision for pituitary macroadenoma. About 8 hours post-op, she developed polyuria with urine output of 400 ml/hour, sodium level: 145 mmol/L, urine sodium: <20 mmol/L, serum osmolality: 299 mmol/L, urine osmolality: 110 mmol/L which was consistent with central DI. Subcutaneous desmopressin was given on days 1 to 3 post-op. On day 7 post-op, she developed SIADH as evidenced by serum osmolality of 241 mmol/L, urine osmolality of 527 mmol/L and urine sodium of 124 mmol/L. Upon entering day 11, she had another episode of polyuria (200 ml/hour). Laboratory tests revealed serum sodium: 126 mmol/L, serum osmolality: 269 mmol/L, urine osmolality: 111 mmol/L and urine sodium: 111 mmol/L which were suggestive of central DI in the triphasic phase. Hence, subcutaneous desmopressin was resumed. Sodium levels normalized and she was discharged home clinically well on sublingual desmopressin.

CONCLUSION
Although triphasic phase of central DI is relatively rare, it is important to identify the phase, as the treatment differs depending on the phase.