Diabetes insipidus

• Facts:
  Failure to concentrate urine (opposite of SIADH ), two kinds of DI
  In central DI, posterior pituitary fails to produce ADH
  In nephrogenic DI, kidneys fail to respond to ADH
  
• History / PE:
  Polyuria, polydipsia
  Patients report a preference for cold beverages
• Diagnosis:
  Water suppression test
  Hypernatremia
• Treatment:
  IV normal saline (patient hypotensive, dehydrated)
  Intranasal or oral DDAVP (central DI)
  Salt restriction and water intake (nephrogenic DI)
• Notes:
  Desmopressin (DDAVP), synthetic analog of ADH , helps distinguish central from nephrogenic DI. In CDI, DDAVP will decrease urine output and increase urine osmolarity. In NDI, DDVAP will not affect urine output
• Associated With:
  Central DI
  Ischemia ( Sheehan’s syndrome )
  Traumatic cerebral injury
  Infection
  Autoimmune disorders
  
  Nephrogenic DI
  Renal diseases
  Drugs ( lithium , demeclocycline )
• Differential Diagnosis:
  Psychogenic polydipsia ( rule out by performing "water deprivation test", if urine becomes concentrated then psychogenic polydipsia, if urine still dilute then DI )