diabetes insipidus (DI)

Classification

• nephrogenic diabetes insipidus
• central diabetes insipidus
• gestational diabetes insipidus (placental vasopressinase)

Pathology

• antidiuretic hormone (ADH)/vasopressin deficiency (central diabetes insipidus) or inactivity (nephrogenic diabetes insipidus)

History

• head trauma, recent neurosurgery
• pituitary disease, renal disease, psychiatric disease
• lithium carbonate use

Clinical manifestations

• polydipsea, cravings for water or cold liquids
• polyuria
  • urinary frequency
  • nocturia, enuresis
  • partial deficiency of ADH usually does not result in polyuria because the maximum urine osmolality is still high enough so that the daily solute load can be excreted in a volume of < 3 liters
• visual field defects, amenorrhea, galactorhea, adrenal insufficiency, or hypothyroidism suggest central diabetes insipidus

Laboratory

• urine osmolality
  • low urine osmolality (< 275 mOsm/L)*
  • response of urine osmolality to water deprivation test
    • close monitoring indicated
    • inability to concentrate urine in response to water deprivation
    • urine osmolality normally increases with water deprivation
  • desmopressin stimulation test
    • when urine does NOT concentrate with water deprivation
    • an increased urine osmolality indicates central DI
    • a lack of response indicates nephrogenic DI
    • patients with primary polydipsia may show response similar to nephrogenic DI due to washout of the medullary concentration gradient
• high serum osmolality (> 290 mOsm/L)*
• low urine specific gravity
• serum sodium is high or high normal* due to free water diuresis
  • if serum sodium is normal, perform water deprivation test
• 24 hour urine volume > 50 mL/kg/24 hr*
• plasma arginine vasopressin (AVP, ADH)
  • low antigen level consistent with central diabetes insipidus
    • ADH level refers to antigen level not activity level
  • plasma copeptin# distinguishes diabetes insipidus from primary polydipsia
    • activity low in diabetes insipidus
    • not widely available
• serum glucose to rule out diabetes mellitus
• serum calcium, serum albumin, serum PTH if hypercalcemia
• high or high normal serum sodium with serum osmolality > urine osmolality suggests diabetes insidipus as cause of polyuria

* initial diagnostic tests makes diagnosis

# fragment of the arginine vasopressin prohormone

Radiology

• CT or MRI of hypothalamus & pituitary if desmopressin stimulation test is positive
• renal ultrasound if desmopressin test is negative (urine does not concentrate)

Differential diagnosis

• diabetes mellitus
  • osmotic diuresis (normal serum glucose suggests diabetes indipidus)
• psychogenic polydipsea

Management

• general
  • correct hypernatremia
  • correct hypovolemia
  • decrease solute load with moderate protein restriction
  • decrease delivery of solute to distal tubule
    • thiazide diuretics
    • low sodium diet
• D5W-1/2 normal saline 1st line treatment after neurosurgery or head trauma; add IV desmopressin if urinary output is excessive or electrolyte abnormalities develop
• intranasal arginine vasopressin (desmopressin) for central DI
  • may be administered orally
• subcutaneous desmopressin
• thiazide diuretics & dietary salt restriction for nephrogenic DI (not drug-induced)
• amiloride for lithium carbonate induced nephrogenic DI

More general terms

• chronic metabolic disease
• neuroendocrine disease

More specific terms

• central diabetes insipidus; diabetes insipidus, neurohypophyseal type (CDI)
• nephrogenic diabetes insipidus (NDI)

Additional terms

• nocturia
• polyuria
• urine osmolality
• vasopressin (antidiuretic hormone, ADH)

Patient information

diabetes insipidus patient information