LAUSR

Nocturnal enuresis (NE) is generally observed in about 20% of preschoolers (5–6 years old) and declines to about 10% in the early elementary school years. However, NE remains in about 5% of children over 10 years of age and nocturia decreases to ≤3% in junior high school students, but does not improve much thereafter and remains in about 0.5% of adults. NE is defined as intermittent, urinary incontinence during sleep that occurs at least once a month for at least 3 months in children aged ≥5 years of age. There is no single cause of NE and multiple factors are thought to be involved. Typical causes of NE include nocturnal polyuria, overactive bladder, and disturbances in arousal as well as developmental disabilities and genetic predisposition. Of note, nocturnal polyuria has been reported in several studies. Rittig et al. showed that nocturnal polyuria in children with NE was caused by a decrease in the amount of antidiuretic hormone secreted during the night compared with children without NE. They reported that NE in children might be due to an abnormal circadian rhythm of antidiuretic hormone secretion, indicating that less antidiuretic hormone is secreted at night than in children without NE. However, abnormalities in the circadian rhythm of antidiuretic hormone secretion are not observed in all children with nocturnal polyuria. In particular, nocturnal polyuria is associated with increased urinary sodium and urea nitrogen, nocturnal hypercalciuria is associated with the decreased secretion of antidiuretic hormone and consequent nocturnal polyuria, and the renal glomerular filtration rate is associated with a loss of circadian rhythm. Criteria for nocturnal polyuria have been proposed by the International Children’s Continence Society (ICCS) and Rittig et al. However, most pediatricians in Japan use the criteria of Hoashi or Akashi because the criteria used in Europe and the US may not be appropriate for Japanese children, who have a different body size compared with Western children (Table 1). However, to date, there have been few studies comparing international and Japanese criteria for the diagnosis of nocturnal polyuria in Japanese children with NE. Nishizaki et al. reported the results of a comparison of Hoashi’s criteria for nocturnal polyuria in Japanese pediatric NE with those used in Europe and the US. The results showed that 17% of patients met Hoashi’s criteria and ICCS criteria, and 26% met Hoashi’s criteria and Ritting’s criteria. Therefore, most patients diagnosed with nocturnal polyuria by Hoashi’s criteria would not be diagnosed as such when using the international criteria. Furthermore, there was no statistically significant difference in the response to desmopressin, a first-line drug for the active treatment of nocturnal polyuria, between the ICCS and Ritting’s groups. This report clearly shows that it is difficult to apply the international criteria for nocturnal polyuria to Japanese pediatric patients with NE because of differences in body size. Further discussion on the definition of nocturnal polyuria at international conferences is needed to establish a formula that considers the patient’s height and weight.