Circadian rhythm of urinary water and solute excretion in children with enuresis

Title: CIRCADIAN RHYTHM OF URINARY WATER AND SOLUTE EXCRETION IN CHILDREN WITH ENURESIS Authors: KARAMARIA S, DELENS V, DOSSCHE L, RAES A, SNAUWAERT E, VANDE WALLE J Background: Enuresis is caused by nocturnal urine production and functional bladder capacity mismatch. ICCS defines nocturnal polyuria (NP) as nocturnal diuresis (ND) >130% of Expected Bladder Capacity (EBC). It is well documented as a pathogenetic mechanism in monosymptomatic, but little is known of its incidence/characteristics in non-monosymptomatic enuresis. NP is attributed to the abnormal circadian rhythm of vasopressin (AVP). However, 40-60% of patients treated with desmopressin show insufficient response, suggesting other factors like nutrition and circadian rhythm of other renal functions may be involved. Aim: study the circadian rhythm on water and solute excretion in fractionated urine samples over 24h (4-day and 4-night samples) Methods: retrospective analysis of 403 children divided in 3 groups a) low-normal ND (<100% EBC, n=171) b) high-normal ND (≤100-129% EBC, n=93) c) NP (≥130% EBC, n=139). Results: NP and high-normal ND groups demonstrate an increased diuresis rate overnight and an abnormal circadian rhythm of diuresis (p=0,001) and osmolar excretion (p<0,001), predominantly in the two first nighttime samples. Children with NP produced more urine (p<0,003) and excreted more osmols (p<0,001) overnight but also at daytime and in a 24h-period. Conclusions: Our data suggest that NP is better defined as ND>100% EBC; this population might be equally desmopressin responsive. Pathogenesis is more complex than an abnormal AVP circadian rhythm: in 60% of patients, abnormalities of other renal circadian rhythms and/or increased nutritional intake might be involved. ND is the highest and osmolality the lowest early in the night; treatment should rather target a fast actio