Diabetes Insipidus Flashcards
Describe diabetes insipidus
Inability of the kidneys to concentrate urine caused by absolute or relative deficiency in
ADH/vasopressin -> hypotonic polyuria (urine osmolality <300)
What are the causes/risk factors of diabetes insipidus?
Central/cranial – failure of ADH secretion from neurohypophysis • Idiopathic • Tumours e.g. pituitary, craniopharyngioma • Infiltration e.g. sarcoidosis • Infection e.g. meningitis • Vascular e.g. Sheehan’s syndrome, SAH • Trauma e.g. head injury, surgery • Genetic e.g. Wolfram’s syndrome (DI, DM, optic atrophy, sensorineural deafness)
Nephrogenic – insensitivity of collecting duct to ADH • Idiopathic • Drugs e.g. lithium • Infiltration e.g. renal sarcoidosis, amyloidosis • Post-obstructive uropathy • Pyelonephritis • Pregnancy • Osmotic diuresis e.g. diabetes mellitus
What are the symptoms of diabetes insipidus?
- Polyuria
- Polydipsia
- Nocturia
- Enuresis in children
Symptoms of hypernatraemia
• Irritability
• Restlessness
What are the signs of diabetes insipidus?
gns
• Urine output >3L/24hr
Signs of dehydration • Tachycardia • Reduced tissue turgor • Postural hypotension • Dry mucous membranes
Signs of hypernatraemia • Spasticity • Hyperreflexia • Delirium • Seizures • Coma
What investigations are carried out for diabetes insipidus?
• Bloods
- U&Es – hypernatraemia
- Increased plasma osmolality
- Decreased urine osmolality
• Urine dipstick – exclude diabetes mellitus
• Water deprivation test
- Water is restricted for 8h
- Plasma and urine osmolality is measured every hour
- Patient is weighed every hour to monitor levels of dehydration
- Desmopressin is given after 8h
• Pituitary MRI
What is the management for diabetes insipidus?
Management Central • Intranasal DDAVP (desmopressin) • Oral/IV fluids Nephrogenic • Treat the underlying the cause • Maintain adequate fluid intake • Sodium restriction • Thiazide diuretics
What are the complications of diabetes insipidus?
• Hypernatraemic dehydration
