Effect of desmopressin on water and solute circadian rhythms in treatment-naïve children with monosymptomatic enuresis and nocturnal polyuria

Enuresis has a complex pathophysiology involving nocturnal polyuria, reduced bladder capacity at nighttime, and impaired arousability. Desmopressin has long been used as a treatment. However, approximately 30% of children do not fully respond to it, suggesting the involvement of other factors. Solute handling and osmotic excretion have been studied in refractory patients. Nevertheless, data on the effect of desmopressin on these factors are sparse. We conducted a post hoc analysis of the SLEEP study. We analyzed the circadian rhythm of solute and water excretion before and after desmopressin in 30 children with monosymptomatic enuresis and nocturnal diuresis > 100% of expected bladder capacity by means of a 24-h urine concentration profile (four daytime and four nighttime urine portions at equivalent time intervals). Under desmopressin, nocturnal diuresis (rate) and Na/creatinine ratio were significantly lower compared to day values (p = 0.009, p = 0.021, respectively). Osmolality, Na/creatinine, and osmotic excretion showed a significant day vs. night variance only after desmopressin. Nighttime osmotic and sodium excretion were significantly lower (p = 0.004, p = 0.019, respectively) under treatment, indicating the impact of desmopressin on kidney sodium handling. During desmopressin treatment, nocturnal diuresis (rate) showed strong positive correlation with nighttime Na/creatinine (r = 0.436, p