title: Sodium fraction excretion rate in nocturnal enuresis correlates with nocturnal polyuria and osmolality.
abstract: OBJECTIVE
  We verify the sodium fraction excretion rate (FE Na) and potassium fraction excretion (FE K) rates in monosymptomatic nocturnal enuresis. We also correlate FE Na and FE K to urinary osmolality, nocturnal polyuria and vasopressin in the same population.
  
  
  METHODS
  A total of 438 children 6 to 15 years old (mean age 9.7) presenting with monosymptomatic nocturnal enuresis were recruited from different centers. Inclusion criteria were 3 or greater wet nights a week, no daytime incontinence and no treatment in the previous 2 months. Exclusion criteria were cardiopathy, endocrinopathy, psychiatric problems and urinary tract abnormalities. Micturition chart, diurnal (8 am to 8 pm) and nocturnal (8 pm to 8 am) urine collection, including separate diuresis volumes, (Na, K and Ca) electrolytes and osmolality were evaluated, as well as serum electrolytes, creatinine and nocturnal (4 am) vasopressin. Diurnal and nocturnal FE K and FE Na were calculated. ANOVA test, chi-square test, Student's t test and Pearson correlation test were used for statistical analysis.
  
  
  RESULTS
  : Nocturnal polyuria (diurnal to nocturnal diuresis ratio less than 1) was found in 273 children (62.3%, group 1 and nocturnal urine volumes were normal in 165 with enuresis (37.7%, group 2). Nocturnal FE Na was abnormal in 179 children (40.8%), including 118 in group 1 (43.2%) and 61 in group 2 (36.9%) (chi-square not significant). FE Na was also increased in nocturnal versus daytime diuresis (Student's t test p <0.001). In group 1 nocturnal FE Na correlated with nocturnal diuresis (Pearson correlation p = 0.003, r = +0.175), while daytime FE Na and nocturnal FE Na correlated with diurnal diuresis (Pearson correlation p = 0.001, r = +0.225 and Pearson correlation p = 0.001, r = +0.209, respectively). In group 2 nocturnal FE Na did not correlate with diuresis (Pearson correlation p = 0.103, r = +0.128) but correlated with vasopressin values (Pearson correlation p = 0.042, r = -0.205). Urine osmolality was reduced in 140 children (31.9%) and correlated with nocturnal diuresis (Pearson correlation p = 0.003, r = -0.321). Vasopressin was decreased in 332 children (75.8%, 62.6% in group 1 and 13.2% in group 2). No significant difference was found between sexes and age of enuretic subgroups.
  
  
  CONCLUSIONS
  Nocturnal FE Na correlates with nocturnal diuresis, whereas daytime FE Na does not. FE K in daytime and nighttime diuresis does not statistically differ in nocturnal polyuric and nonpolyuric enuretic groups. Osmolality correlates with nocturnal diuresis, and vasopressin at 4 am was lower in the nocturnal polyuric group. The hypothesis of a subset of enuretic patients presenting with nocturnal polyuria associated with high nocturnal natriuria and low vasopressin values has been confirmed.
authors.affiliation: Department Biomedicina Età Evolutiva, University, Bari, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Aceto
authors.forename: Rosa
authors.initials: R
authors.lastname: Penza
authors.forename: Maurizio
authors.initials: M
authors.lastname: Delvecchio
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Chiozza
authors.forename: Marcello
authors.initials: M
authors.lastname: Cimador
authors.forename: Paolo
authors.initials: P
authors.lastname: Caione
mesh_terms: D000293:Adolescent; D002648:Child; D004775:Enuresis / Q000150:complications* / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D011141:Polyuria / Q000150:complications*; D011188:Potassium / Q000652:urine; D012964:Sodium / Q000652:urine*; D014667:Vasopressins / Q000652:urine
chemical_list: D014667:Vasopressins; D012964:Sodium; D011188:Potassium