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Nephrogenic Diabetes Insipidus (Symptoms (Aetiology (Renal tubular…
Nephrogenic Diabetes Insipidus
Symptoms
Aetiology
Renal tubular acidosis
Sickle cell disease
Drugs; lithium chloride, glibenclamide
Prolonged polyuria of any cause
Hypercalcaemia
Familial - mutation of ADH receptor
Hypokalaemia
Polyuria - 15L in 24hrs
Compensatory polydipsia - thirsty
No glycosuria
Hypernatraemia due to water loss in EXCESS of Na loss
Can lead to dehydration which can be severe if the thirst mechanism or consciousness is impaired or the patient is denied fluid
Pathophysiology
Impaired response of the kidney to ADH
This results in significant water losses resulting in dilute urine
Investigations
Check blood glucose to exclude diabetes mellitus
Water deprivation test
To differentiate between different types of DI, give desmopressin
Urine will not be concentrated in nephrogenic DI
Urine volume measured to confirm polyuria - DI is unlikely if urine volume < 3L/day
MRI of hypothalamus - to look for masses
Treatment Plan
Give thiazide diuretics (work in the DCT) - will produce mild hypovolaemia, which encourages the kidneys to take up Na/water in PCT
NSAIDs - Lower urine volume and plasma Na by inhabiting prostaglandin synthase - these usually locally inhibit the action of ADH
Treat the cause - usually renal disease