Nocturnal polyuria in monosymptomatic nocturnal enuresis (MNE) has so far mainly been attributed to a disturbed circadian rhythm of renal water handling. Low vasopressin levels overnight correlate with absent maximal concentrating activity, resulting in an increased nocturnal diuresis with low urinary osmolality. Therefore, treatment with desmopressin is a rational choice. Unfortunately, 20 to 60 % of children with monosymptomatic enuresis are desmopressin-resistant. There is increasing evidence that other disturbed circadian rhythms might play a role in nocturnal polyuria. This review focuses on renal aspects in the pathophysiology of nocturnal polyuria in MNE, with special emphasis on circadian rhythms. Articles related to renal circadian rhythms and enuresis were searched through the PubMed library with the goal of providing a concise review.
CONCLUSION:
Nocturnal polyuria can only partially be explained by blunted circadian rhythm of vasopressin secretion. Other alterations in the intrinsic renal circadian clock system also seem to be involved, especially in desmopressin-resistant enuresis.
WHAT IS KNOWN:
• Disturbance in the circadian rhythm of arginine vasopressin secretion is related to nocturnal polyuria in children with enuresis.
• Desmopressin is recommended as a treatment for monosymptomatic nocturnal enuresis, working as a vasopressin analogue acting on V2 receptors in the collecting ducts of the kidney.
What is New: • Other renal circadian rhythms might play a role in nocturnal polyuria, especially in desmopressin-resistant case.
This article is an excellent review, summary and overview of the literature specifically regarding the circadian rhythm of the renal physiology. The authors conclude that “there is not just one kind of nocturnal enuresis”, but that it is a complex disorder involving multiple pathogenetic factors. The bladder is involved, the sleep pattern, but also the kidney. The circadian rhythm of urine production is dependent on many factors such as volume load, blood pressure, obstructive breathing, vasopressin, an intrinsic renal circadian clock system, sodium-regulating hormones and probably other undiscovered ones.