Diabetes Insipidus (DI)
- Impaired water reabsorption due to ADH deficiency
- Types: central (brain unable to make ADH), nephrogenic (ADH resistance)
- Features: polyuria, polydipsia, dehydration
- Biochemistry: increased serum osmolality/sodium, decreased urine osmolality/sodium
- Central DI causes: 50% idiopathic, head injuries, tumours, infections, sarcoidosis
- Nephrogenic DI causes: lithium, hypercalcaemia, pyelonephritis, hydronephrosis
- Investigation: water deprivation test
- Treatment: central DI – desmopressin, nephrogenic DI – thiazide diuretics