CHARACTERISTICS OF NYCTHEMERAL RHYTHM OF URINARY WATER AND SOLUTE EXCRETION IN CHILDREN WITH
ENURESIS
Sevasti Karamaria
1,2, Vincent Delens
2, Lien Dossche
1,2, Ann Raes
1,2, Johan Vande Walle
1,2CONTACT
PEDIATRIC NEPHROLOGY DEPARTMENT
+32 (0)9 332 52 71
sevasti.karamaria@uzgent.be www.uzgent.be
1Department of Pediatric Nephrology, UZ Gent, Ghent, 2Ghent University
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METHODS
Our aim was to study the circadian rhythm of the kidney on water and solute excretion in fractionated urine samples over 24hours (4 day and 4 night samples).
We conducted a retrospective analysis of data from 402 enuretic children by whom a 24h urine concentration profile at a home setting was performed.
The children were divided according to nocturnal diuresis into 3 subgroups based on the ICCS definition:
a) low-normal ND if ND was <90% of EBC (113 cases)
b) high-normal ND if ND was 90-130% of EBC (103 cases) c) NP if ND was >130% of EBC (91 cases)
BACKGROUND
Nocturnal enuresis (NE) is caused by a mismatch of the nocturnal urine production and the functional bladder capacity. The International Children’s Continence Society (ICCS) defined nocturnal polyuria (NP) as nocturnal diuresis (ND) exceeding the Expected Bladder Capacity (EBC) by 130%. NP is well documented as pathogenetic mechanism in monosymptomatic, but little is known of its incidence/characteristics in non monosymptomatic NE. NP, when associated with increased water diuresis, is attributed to abnormal circadian rhythm of vasopressin (AVP). This is why NE is treated with desmopressin, an AVP agonist. However 40-60% of the patients show insufficient response to it, suggesting that other factors like nutrition and circadian rhythm of other renal functions may be involved
The predominant findings are observed in both groups in the two first nighttime samples.
The NP as well in the high-normal ND group demonstrated:
• increased diuresis rate and free water clearance overnight (Figure 1)
• abnormal circadian rhythm of diuresis (p=0,001) (Figure 1)
• abnormal circadian rhythm of osmolar excretion (p<0,001) (Figure 2a,b)
Children with NP demonstrated a higher urine output not only at night but also during the daytime and in a 24h period (p<0,003) compared to the other groups.
We observed higher absolute volumes (Figure 1a,b) in these intervals, as well as smaller difference between the daytime and nighttime output in the NP group (Figure 2b)
The same pattern was observed for osmoles excretion (p<0,001) in the NP group (Figure 4a,b) compared to the other groups.
Figure 1
Figure 2b Figure 2a
Figure 3a
Figure 4b Figure 4a
Figure 3b
REFERENCES
1. Dossche L, Walle JV, Van Herzeele C. The pathophysiology of monosymptomatic nocturnal enuresis with special emphasis on the circadian rhythm of renal physiology. Eur J Pediatr. 2016;175(6):747-54 2. Dossche L, Raes A, Hoebeke P, De Bruyne P, Vande Walle J. Circadian Rhythm of Glomerular Filtration and Solute Handling Related to Nocturnal Enuresis. J Urol. 2016;195(1):162-7.
3. Van Herzeele C, Evans J, Eggert P, Lottmann H, Norgaard JP, Vande Walle J. Predictive parameters of response to desmopressin in primary nocturnal enuresis. Journal of pediatric urology. 2015;11(4):200.e1-8.
CONCLUSION
Where the clinical indication for desmopressin is often restricted to children with MNE and NP (>130%EBC), our data suggest that:
• Desmopressin response might be expected in MNE and NMNE when Nocturnal Diuresis rate is >100% EBC, since maximal concentrating capacity is not reached overnight.
• Overall pathogenesis of high diuresis rate overnight is more complex than AVP related, since in up to 60% of patients, abnormalities of other circadian rhythms of renal functions are involved, as well as increased osmotic load by nutritional intake.
• NP is the highest and U osmolality the lowest in the early night collections, thus treatment should target fast rather than long term action.
IWT-SBO 130033
