Diabetes Insipidus

#med #disease #y2023 #renal #neuro

Presentation :

Presents with polydipsia, polyuria, nocturia
If resulting from a pituitary tumor, may also present with classic visual field deficits

Plasma glucose level to rule out diabetes mellitus as cause of polyuria.
Serum calcium level to rule out hypercalcemia as cause of polyuria.
An inappropriately low urine osmolality in the setting of an elevated serum osmolality and hypernatremia in a patient with polyuria is diagnostic.
- A water deprivation test can be performed when the diagnosis is uncertain. Following water deprivation, an elevated serum osmolality or hypernatremia with inappropriately dilute urine is diagnostic.
Evaluating the response to desmopressin can help differentiate central from nephrogenic DI.
- If the desmopressin challenge test is positive (urine concentrates, indicating central DI), order an MRI of the pituitary gland.
- If the test is negative (urine does not concentrate, indicating nephrogenic DI), order kidney ultrasonography.