Diabetes insipidus

Pathophysiology

• ADH deficiency or ADH resistance

Differential Diagnosis

• Psychogenic polydipsia (though usually hyponatremic)
• Central diabetes insipidus (ADH deficiency)
  • Pituitary adenoma
  • Brain metastases
  • Post-neurosurgery
• Nephrogenic diabetes insipidus (ADH resistance)
  • Lithium toxicity?

Clinical Manifestations

• History
  • Polyuria
  • Polydipsia
  • Nocturia
• Signs & Symptoms

Investigations

• Labs
  • Random blood glucose to rule out diabetes
  • SNa, expected to be eunatremic or hypernatremic due to free water loss
  • Ulytes and Uosm, expected to be dilute
  • Water deprivation test
  • Trial of ddAVP if known or suspected hypopituitarism
• Imaging
• Other

Management

• Acute
  • Central
    • ddAVP dose to urine output
    • If post-transsphenoidal resection of the pituitary, it is often transient and should recover without intervention within 24h
• Chronic