84. A 7-year-old boy who had surgery for craniopharyngioma 2 days ago now has increased thirst and frequent urination. He has no vomiting, blurry vision, or seizures. His current medication includes phenytoin. He has a heart rate of 102 beats/min, a respiratory rate of 16 breaths/min, and a blood pressure of 102/60 mm Hg. He has no swelling over his body. His craniotomy incision site is clean and healing. He has no neurological deficits, and the rest of his physical examination findings are unremarkable. Laboratory data are shown: Sodium 150 mEq/L (150 mmol/L Potassium 4.2 mEq/L (4.2 mmol/L Chloride 110 mEq/L (110 mmol/L Bicarbonate 23 mEq/L (23 mmol/L Blood urea nitrogen 28 mg/dL (10.0 mmol/L Creatinine 0.5 mg/dL (44 mol/L Glucose 90 mg/dL (5.0 mmol/L Serum osmolality 325 mOsm/kg (325 mmol/kg Urine Specific gravity 1.006, Leukocyte esterase, Negative, Nitrite-Negative, Blood-Negative, Protein- Negative, Glucose- Negative of the following, the MOST likely diagnosis for this child is a. acute kidney injury b. central diabetes insipidus c. cerebral salt wasting d. syndrome of inappropriate secretion of antidiuretic hormone