POLYURIA / POLYDIPSIA

raised osmotic load:

diabetes mellitus

chronic renal disease

[early with any cause of chronic renal failure due to raised GFR in remaining nephrons; oliguria occurs later]

decreased renal response to ADH:

[=nephrogenic diabetes insipidus; normal or high ADH; inappropriately low urine osmolarity, in spite of high serum osmolarity; urine osmolarity does not rise after water deprivation and ADH administration]

drugs:

demeclocycline (ADH antagonist)

other:

inherited [1� nephrogenic diabetes insipidus; idiopathic]

lack of ADH:

[=cranial diabetes insipidus; low ADH; inappropriately low urine osmolarity, in spite of high serum osmolarity; urine osmolarity does not rise during water deprivation test but rises after ADH administration]

pituitary or hypothalamic tumours:

genetic (isolated or associated with diabetes mellitus in DIDMOAD syndrome = diabetes insipidus, diabetes mellitus, optic atrophy, deafness)

other causes:

psychogenic polydipsia [urine osmolarity rises during water deprivation test]

recovery phase of heart failure or nephrotic syndrome (elimination of oedema fluid)

following relief of outflow obstruction, eg. post-TURP

recovery phase of acute tubular necrosis