Background. Monosymptomatic nocturnal enuresis (MNE) is defined as involuntary nighttime urination of children over five years of age without any congenital or acquired defect in the central nervous system. Many factors, mainly nocturnal polyuria, sleep disorders, decreased bladder capacity, and bladder dysfunctions play a role in the etiology of MNE.

Methods. Eighty-three children diagnosed with MNE were included in the study. Complete blood cell count, blood biochemistry, renin, and aldosterone levels of all children were obtained. Twenty-four-hour urine samples were collected separately daytime and nighttime and urinary electrolytes were evaluated. Also, 24-hour ambulatory blood pressure monitoring (ABPM) was performed for each patient. The results were evaluated by comparing both enuretic children vs. control group and enuretic children with polyuria vs. without polyuria.

Results. When we compared the enuretic children and the control group in terms of urinary electrolytes, the fractional excretion of sodium (FENa) and fractional excretion of potassium (FEK) values of the enuretic group were higher than the control. The evaluation of the 24-hour ABPM findings revealed no significant difference in terms of the mean arterial pressure (MAP) and diastolic blood pressure (DBP) during the daytime and nighttime measurements. The daytime systolic blood pressure (SBP), however, was significantly lower in the enuretic group. When enuretic children with and without polyuria and the control group were compared, the nighttime, FENa, FEK, as well as nighttime urinary excretion of calcium and protein were significantly higher in enuretic children with polyuria. No difference was detected on the MAP, SBP, or DBP values.

Conclusions. In conclusion, the nighttime urinary solute excretion of enuretic children was found to be higher and this condition may especially be associated with pathogenesis of nighttime polyuria. In enuretic children, nighttime blood pressure changes were not influential in the etiopathogenesis in all patient groups and multiple mechanisms may play a role in the pathogenesis of enuresis.

Keywords: ambulatory blood pressure, enuresis, urinary electrolyte excretion