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Increased renal concentrating ability after long-term oral desmopressin lyophilisate treatment contributes to continued success for monosymptomatic nocturnal enuresis
Hirokazu Ikeda, Tsuneki Watanabe and Keiichi Isoyama - Department of Pediatrics, Showa University Fujigaoka Hospital, Yokohama, Kanagawa, Department of Pediatrics, Showa University, Tokyo, Japan
Commentary by Konstantinos Kamperis
Improved renal concentrating capacity in children that remain dry at night following desmopressin treatment. The result of long-term desmopressin treatment?
Desmopressin is first line treatment in nocturnal enuresis with response rates varying depending on the treated population characteristics. The current understanding is that desmopressin is effective while used and discontinuation of the medication is related to high relapse rates. Up to date there is no evidence that desmopressin treatment leads to any sustainable changes in renal function or circadian rhythm of ADH. The authors of this study retrospectively evaluated children that were full responders to desmopressin and attempted to answer the question: Why do some children experience relapse after discontinuation of the medication whereas other remain dry.
The authors hypothesized that children that remained dry after discontinuation of desmopressin differ in terms of renal concentrating capacity compared to the ones experiencing relapse of their bedwetting. Fifty-eight children were included in the study with a mean duration of desmopressin treatment of 18 months. Data on nocturnal urine production as well as the first morning urine osmolality were compared between children who relapse after desmopressin discontinuation and the ones that remained dry. The authors were able to demonstrate that children experiencing relapses shared a higher nocturnal urine output and less concentrated urine during dry nights indicating that these children continue to be in risk of excess urine production and thus enuresis.
The authors discuss methodological limitations of the study, the main being the fact that urine output on wet nights was not measured and thus one cannot conclude on the exact mechanisms that lead to wet nights after desmopressin discontinuation.
However, the most important point that needs to be stressed is that the observed changes in the renal concentrating ability in children that become dry on desmopressin are not necessary the result of desmopressin treatment per se. As enuresis has a significant spontaneous cure rate the changes in the renal parameters described in this paper may be the result of alterations in lifestyle, spontaneous changes related to age or other factors.
Whether desmopressin leads to long-term changes in the renal environment is still a hypothesis that needs further investigation.