Background. Central diabetes insipidus (CDI) is a fairly common complication of neurosurgical removal of the chiasmal-sellar region (CSR) tumors. In some cases, postoperative CDI has a three-phase course. At the same time, each of the stages of the condition requires a differentiated approach based on the obtained clinical and laboratory data.
Description of the clinical case. A description of the three-phase course of CDI that developed in a child after neurosurgical removal of a giant endosuprasellar craniopharyngioma is presented. Determining the phase of the process was based on indicators of water bal- ance, blood serum electrolytes and osmolality, urine osmolality. During the first and third phases, normo- and hypernatremia (140–153 mmol/l) with simultaneous polyuria and polydipsia was noted; the second phase was characterized by hyponatremia (132–134 mmol/l), high-normal urine osmolality (790–1190 mOsm/kg), oliguria and lack of thirst. During the first and third phases, substitution therapy with desmopressin preparations was carried out with a free drinking regimen. During the second phase, fluid intake was sharply limited in combination with dietary salt supplementation (3–5 g/day) and desmopressin withdrawal.
Conclusion. The course of diabetes insipidus after neurosurgical removal of the CSR tumor requires careful monitoring in the postop- erative period. Timely detection of the three-phase course of CND and a differentiated approach to the tactics of managing a child in each of the phases make it possible to avoid significant excursion in the blood electrolyte levels up to the development of life-threatening conditions.

Keywords: craniopharyngioma, three-phase course, central diabetes insipidus