24 -hour Urinary Parameters in Pediatric Stone Formers- Are there Differences in the 1stand 2ndDecades of Life by Gender?
Pankaj Dangle, MD.,Mch, Elena Gibson, BS, Kyle Wood, MD, Dean Assimos, MD, David Joseph, MD.
University of Alabama at Birmingham, Birmingham, AL, USA.
BACKGROUND: The incidence of pediatric urolithiasis has increased in recent years, particularly among adolescents. However, reasons for the increased prevalence of idiopathic urolithiasis during the second decade of life remain undefined. Urinary risk factors are inconsistently recognized in pediatric patients, and the link between the rising incidence of idiopathic urolithiasis in the 2nddecade of life and urinary risk factors also remains ill-defined. Therefore, we aimed to assess differences in urinary parameters among pediatric urolithiasis patients by decade of life and gender.
METHODS: We conducted a single-center retrospective evaluation of our pediatric stone database and identified non-cystinuric patients with 24-hour urine studies. Patients were stratified by age and gender for comparison.Due to concerns about the normality of variables, means between the age and gender groups were compared using the nonparametric Wilcoxon rank-sum test. Gender differences and metabolic abnormalities between age groups were compared using the chi-square test. RESULTS: Eighty-eight (34%) patients ages 1-10 years (Group 1) and 174 (66%) patients ages 11-18 years (Group 2) were identified. Females made up the majority of patients in Group 1 (64%) and Group 2 (58%), and gender distribution was similar between age groups (p=0.38). Among all patients, 177 metabolic risk factors were identified. Hyperoxaluria was the most common (n=63) followed by hypercalciuria (n=56) and hypocitraturia (n=36). Compared to Group 1, patients in the second decade of life (Group 2) had lower mean weight-adjusted levels of calcium (2.70 vs 3.56 mg/kg p<0.001) and oxalate (34.55 vs 41.73 mg/1.73m2p=0.033). Similarly, hypercalciuria was more common during the 1stdecade of life compared to the 2nd(33% vs. 16%; p=0.002) Differences in parameters by gender are outlined in Table 1. In both decades of life, there were no significant differences in volume, calcium, or oxalate by gender. Hypocitraturia was more common among males (p<0.001) and mean urinary citrate levels were significantly higher among females. Although females ages 11-18 years comprised 39% of all patients, they accounted for only one fourth of the metabolic risk factors identified. CONCLUSIONS: Although the majority of patients studied were female, urinary risk factors associated with female gender were not identified during either decade of life. These results may reflect the presence of unidentified dietary or hormonal differences between genders, and future efforts should be made to determine associated factors.
| 24 Hour Parameters Mean(SD) and **N(%) | Group 1 FemaleN=56 (64%) | Group 1MaleN=32 (36%) | p(Wilcoxon and *Chi-Square) | Group 2 FemaleN=101 (58%) | Group 2Male N=73 (42%) | p(Wilcoxon and *Chi-Square) |
| Volume | 0.67 (0.31) | 0.71 (0.32) | .60 | 0.94 (0.38) | 1.03 (0.56) | .49 |
| pH | 6.52 (0.53) | 6.41 (0.55) | .27 | 6.34 (0.50) | 6.29 (0.46) | .27 |
| Citrate (mg) | 367.5 (177.4) | 340.5 (192.7) | .41 | 584.7 (308.3) | 439.7 (228.9) | .001 |
| Calcium/Weight(mg/kg) | 3.76 (1.66) | 3.23 (2.26) | .07 | 2.75 (1.34) | 2.62 (1.52) | .54 |
| Oxalate (mg/1.73m2) | 41.53(22.40) | 42.04 (19.36) | .97 | 34.80 (12.06) | 34.28 (13.91) | .84 |
| Hypercalciuria**Ca/Weight >4 | 20 (36%) | 9 (28%) | .46* | 17 (17%) | 10 (14%) | .57* |
| Hyperoxaluria**>40/1.73m2 | 20 (36%) | 13 (41%) | .65* | 16 (16%) | 14 (19%) | .61* |
| Hypocitraturia**<310mg/1.73m2females <365 males | 1 (1.8%) | 9 (28%) | .002* | 5 (5%) | 21 (29%) | <.001* |
| Hyperuricosuria**(>.815mg/1.73m2) | 6 (11%) | 4 (13%) | .80* | 7 (7%) | 5 (7%) | .98* |
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