Diabetes Insipidus

Diabetes Insipidus


DIABETES INSIPDUS

  • Diabetes insipdus is an uncommon disorder characterised by excretion of excessive urine followed by thirst.

Classification-

  1. Cranial DI (deficient ADH production by hypothalamus)
  2. Nephrogenic DI (renal tubules unresponsive to ADH)

Etiology-

  1. Cranial DI-
  • Structural hypothalamic structure
  • Genetic defect- recessive & dominant

2. Nephrogenic DI-

Genetic

  • Drugs – lithium, Demeclocycline

Metabolic-

  1. Hypokalaemia
  2. Hypercalcaemia

Chronic kidney disease

  1. Polycystic kidney disease
  2. Sickle-cell anaemia
  3. Infiltrative disease

Clinical features-

  • Polyuria (5- 20l), polydipsia, thirst (most marked features)
  • Urine is of low specific gravity and osmolality.
  • Vasopressinase-induced diabetes insipidus – seen in the last trimester of pregnancy and in puerperium

Investigations-

  • Elevated plasma osmolality.
  • Water deprivation test is required- DI is confirmed by plasma osmolality > 300 mOsm/kg with urine osmolality < 600 mOsm/kg.
  • Serum sodium is high.

Treatment-

  • Cranial DI- DDAVP (desmopressin)- orally or IM
  • Nephrogenic DI- thiazide diurectics and salt restriction
  • Treatment of choice for polyuria in lithium induced diabetes insipidus is amiloride.

Exam Important

Classification-

  1. Cranial DI (deficient ADH production by hypothalamus)
  2. Nephrogenic DI (renal tubules unresponsive to ADH)

Etiology-

  1. Cranial DI-
  • Structural hypothalamic structure
  • Genetic defect- recessive & dominant

2. Nephrogenic DI-

Genetic

  •  Drugs – lithium, Demeclocycline

Metabolic-

  1. Hypokalaemia
  2. Hypercalcaemia

Chronic kidney disease

  1. Polycystic kidney disease
  2. Sickle-cell anaemia
  3. Infiltrative disease

Clinical features-

  • Polyuria (5- 20l), polydipsia, thirst (most marked features)
  • Urine is of low specific gravity and osmolality.
  • Vasopressinase-induced diabetes insipidus – seen in the last trimester of pregnancy and in puerperium

Investigations-

  • Elevated plasma osmolality.
  • Water deprivation test is required- DI is confirmed by plasma osmolality > 300 mOsm/kg with urine osmolality < 600 mOsm/kg.
  • Serum sodium is high.

Treatment-

  • Cranial DI- DDAVP (desmopressin)- orally or IM
  • Nephrogenic DI- thiazide diurectics and salt restriction
  • Treatment of choice for polyuria in lithium induced diabetes insipidus is amiloride.
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