The effect of desmopressin on renal water and solute handling in desmopressin resistant monosymptomatic nocturnal enuresis.

PURPOSE: We sought to evaluate the effect of desmopressin on renal water and solute handling in children with monosymptomatic nocturnal enuresis and desmopressin resistant nocturnal polyuria compared to healthy controls.

MATERIALS AND METHODS: A total of 12 patients with enuresis and nocturnal polyuria, normal bladder reservoir function and no response to desmopressin, and 10 age matched controls were enrolled in the study. Children were admitted to the hospital for a 48-hour protocol comprising urine collections and blood sampling. Sodium and water intake was standardized. During the second night children received 40 mug intranasal desmopressin. Parameters characterizing the renal water and solute handling were measured and compared between baseline nights and nights with desmopressin.

RESULTS: Desmopressin markedly reduced nocturnal urine output in patients with enuresis, minimizing sodium, urea and overall solute excretion, despite the fact that these children were unresponsive to desmopressin at home. This effect on renal sodium handling was not mediated by atrial natriuretic peptide, angiotensin II, aldosterone or renin. Desmopressin did not influence urinary prostaglandin E(2) excretion. The antinatriuretic effect was seen only in patients with enuresis, and it was directly correlated with the reduction in urine output.

CONCLUSIONS: Children with nocturnal enuresis and nocturnal polyuria who do not exhibit adequate response to desmopressin at home seem to respond well to the agent at the clinic. The effect of desmopressin in children with enuresis seems largely dependent on reductions in the amount of sodium excreted. Sodium regulating hormones remained unaffected by desmopressin, indicating a possible direct effect of the agent on renal sodium handling.