Risk of diabetes insipidus after pituitary surgery

Diabetes insipidus is a common complication of pituitary surgery, occurring acutely in 18-30% of operations. Most patients recover full posterior function but a minority sustain sufficient damage to vasopressin-secreting neurons to develop permanent diabetes insipidus. The triplephase response, comprising early transient diabetes insipidus, followed by a period of antidiuresis and hyponatremia, before resolving into permanent diabetes insipidus, is an uncommon but important variant. Diabetes insipidus is more common following surgery for craniopharyngioma compared with pituitary adenoma, and craniopharyngioma patients may develop the dangerous complication of adipsic diabetes insipidus. Diabetes insipidus is also more common following pituitary surgery for Rathke's cleft cysts and possible adrenocorticotropic hormone-secreting adenomas. The data on tumor size are conflicting but our own experience would suggest that diabetes insipidus is more common after surgery for large suprasellar tumors, particularly those with hypothalamic extension. The experience and skill of the neurosurgeon also determines the likelihood of developing diabetes insipidus. The diagnosis of postsurgical diabetes insipidus depends on excluding other forms of polyuria, including diabetes mellitus, excess intravenous fluids and therapy with diuretics or mannitol. Treatment with vasopressin analogues is almost always effective in controlling renal water excretion and normalizing plasma sodium concentrations.