Synopsis
Distinguish renal vasopressin resistance from other polyuria, protect against hypernatraemic dehydration, and manage acquired or inherited disease with specialist safeguards.
- Nephrogenic diabetes insipidus is renal resistance to arginine vasopressin, now also termed AVP resistance, causing hypotonic polyuria despite an intact thirst and hormone response.
- Confirm true polyuria by measured volume rather than urinary frequency; in adults a 24-hour output above about 3 litres is a useful threshold but size and intake matter.
- Exclude osmotic diuresis from glucose, urea, mannitol or diuretics and primary polydipsia before undertaking specialised water-balance testing.
Key red flags
Dry mucosae, hypotension, tachycardia, lethargy, irritability, confusion or seizure after reduced water access signals dangerous uncompensated loss.
Investigation priorities
Confirm polyuria and quantify ongoing water loss.
Management branches
A patient reports frequent urination and excessive thirst.
- Distinguish urinary frequency from high volume using a bladder history, fluid chart or complete 24-hour urine measurement.
- Pair urine osmolality with plasma sodium or osmolality and screen glucose, calcium, potassium, renal function and diuretic or SGLT2 use.
Key medicines
Thiazide-type diureticSelect a locally available agent and low starting dose only under renal or endocrine advice, then titrate against measured urine volume, blood pressure and electrolytes.
AmilorideUse specialist-selected dosing from the current formulary, particularly in lithium-associated disease, with early and repeated potassium, creatinine and lithium checks.