Week 11 - Diabetes Insipidus Flashcards
what is diabetes insipidus
- a group of conditions associated w a deficiency in ADH function = inability to conserve water
what can cause DI
- decreased production or secretion of ADH
- or lack of renal response to ADH
what are the 3 types of DI
- central (neurogenic)
- nephrogenic
- primary (psychogenic)
what is the cause of central DI
- brain injury or tumour interfering w ADH synthesis or release
what is the cause of nephrogenic DI
- renal disease where the kidneys fail to respond to ADH
what is the cause of primary/psychogenic DI
- brain lesions effecting thirst regulation or psychological disorder
- excessive water intake
describe what decreased antidiuretic hormone causes
- decreased ADH –> decreased water reabsorption in renal tubules –> decreased intravascular fluid vol –> excessive urine output & increased serum osmolaity (hypenatremia)
what is DI characterized by
- excessive thirst
- excretions of extremely diulte urine
what are symptoms of DI (9)
- “dying of thirst” = polydipsia
- abrupt polyuria (up to 20L/day)
- fatigue
- constipation
- weight loss
- dehydration
- decreased LOC
- shock
- seizures, coma
how is DI diagnosed (4)
- history
- physical exam
- urine & serum osmolality
- water deprivation test
what do you expect urine osmolality to be like during DI? serum?
- urine = low
- serum = high (or normal if compensating well w fluid intake)
what impact does oral intake have on urine osmolalit
- no effect
what is a water deprivation test
- deprive pts of water for 8-16 hrs while monitoring BP & conc of urine
- then give ADH to see if kidneys response
what is the cause of the problem is urine osmolaity increases after water deprivation test
- central (neurogenic) cause
what is the cause of the problem if urine osmolality doesnt change after water deprivation test
- kidneys = nephrogenic
