An 12-year-old child has been diagnosed with Diabetes insipidus.

Explanation

Core Concept: Diabetes Insipidus (DI) is a disorder of water metabolism caused by either a deficiency of antidiuretic hormone (ADH, or vasopressin) or renal resistance to ADH. ADH is synthesized in the hypothalamus but is stored and secreted into the bloodstream by the posterior pituitary gland.

Clinical Presentation:

• Polyuria (excessive urination) and polydipsia (excessive thirst).
• Nocturia, enuresis in children, dehydration, and hypernatremia.
• Low urine specific gravity and dilute urine.

Diagnosis:

• First-line diagnostic plan: Urinalysis showing dilute urine (low specific gravity < 1.005) and serum sodium showing hypernatremia.
• Most accurate (gold standard) test: Water deprivation test followed by administration of desmopressin (DDAVP) to differentiate between central and nephrogenic DI.

Management:

• Acute management: Fluid replacement to correct dehydration and hypernatremia, ensuring free access to water.
• Gold standard long-term management: For central DI, lifelong hormone replacement with intranasal or oral desmopressin (DDAVP). For nephrogenic DI, thiazide diuretics and a low-sodium diet.