Possible causes of nocturnal polyuria:
(1) correctable cause without the need to increase the dose of desmospressin
(2) insufficient dose of desmopressin
(3) desmopressin resistance
Correctable causes:
(1) noncompliance
(2) failure to empty the bladder before going to bed
(3) administration of desmopressin less than 1 hour before last void before sleep
(4) excessive fluid intake after or during the hour after the desmopressin dose
(5) constipation
Causes of desmopressin resistance:
(1) abnormality of maximal concentrating capacity
(2) increased nocturnal osmotic excretion
(3) nycthemeral (24 hour) rhythm of prostaglandins
(4) calciuria
(5) sodium excretion
(6) sleep pattern
(7) dietary intake
(8) increased GFR
(9) nephrogenic diabetes insipidus
(10) psychiatric disorder
Most cases of desmopressin-resistance should be referred to a specialist.
