Exploring potential mechanisms in alarm treatment for primary nocturnal enuresis

In the treatment of childhood nocturnal enuresis the enuresis alarm has consistently proved effective. However, the various proposals advanced to explain its therapeutic mechanism generally lack empirical support. In this clinical trial we investigated the hypothesis that the alarm promotes reduced nocturnal urine production through increased urine concentration (enabling the child to sleep through the night).

Measurements of urinary vasopressin and osmolality were made pre- and post-alarm treatment in a group (n=12) of outpatient children (aged 7-12 years) with severe (more than four times a week) nocturnal enuresis.

Of the study group, 75% achieved the success criteria, with 89% predominantly sleeping through the night on dry nights, confirming that arousability is unlikely to be the principal mode of action. All those becoming dry showed an increase in urine concentration post-treatment. For half this was associated with an increase in post-treatment vasopressin whilst for the rest, although increases in osmolality were observed, there was no associated increase in vasopressin.

Although based on a small sample this study offers an insight into possible therapeutic mechanisms of an enuresis alarm. It suggests that most children who become dry sleep through the night and that increased nocturnal urine concentration (and thus reduced urine volume) is likely to be the means whereby this is achieved. Furthermore, the study suggests two possible mechanisms whereby nocturnal urine concentration is achieved: either increased production of vasopressin or enhanced water transport across the urothelium.