- Email: [email protected]
POTASSIUM RATIOS IN PEDIATRIC STONE FORMERS
Vol. 185, No. 4S, Supplement, Monday, May 16, 2011
form Infrared Spectroscopy (FTIR). Logistic regression analyses were performed to determine differences in the incidence of components based on age, gender and geographic location. For geographic analyses, the United States was divided into regions based on climate (North, South, Midwest, Mountain West and West). RESULTS: A total of 5,245 stones analyses were included in our study, with all 50 states being represented. 44% of stones were submitted from male patients. Calcium was the most common component in both male and female children, being found in 95.6% of stones. Uric acid stones were more common in males (1.4% vs 0.6%, p⬍0.05), while infectious stones were more common in females (4.8% vs 3.8%, p⬍0.05). Stones containing calcium oxalate increased with age (59% 1–5 year olds (yo), 79% 6 –13 yo, 88% 14 –18 yo, p⬍0.05). Stones containing calcium phosphate were more frequent in the youngest age group (75% 1–5 yo, 57% 6 –13 yo, 61% 14 –18 yo, p⬍0.05) and cystine stones were more frequent in younger males (6.1% 1–5 yo, 2.4% 6 –13 yo, 3.5% 14 –18 yo, p⬍0.05). Infectious stones accounted for 4.4% of all stones, and decreased with age (12% 1–5 yo, 6.6% 6 –13 yo, 2.4% 14 –18 yo, p⬍0.05). No significant differences were observed between regions. CONCLUSIONS: This series is the largest stone composition analysis of the U.S. pediatric population to date and the first to represent children nationwide. Our analysis demonstrates age- and genderspecific differences in stone composition. These data indicate stone composition is similar throughout the U.S. and has been consistent over the past several decades. Source of Funding: None
1381 DO PEDIATRIC STONE-FORMERS HAVE A HIGH-SODIUM DIET? ANALYSIS OF 24-HOUR URINE SODIUM/POTASSIUM RATIOS IN PEDIATRIC STONE FORMERS Candace Granberg*, Aditya Bagrodia, Katherine Twombley, Khashayar Sakhaee, Naim Maalouf, Linda A. Baker, Nicol C. Bush, Dallas, TX INTRODUCTION AND OBJECTIVES: Dietary factors may contribute to the rise in pediatric stone disease. Excess sodium (Na) intake, which necessitates calcium (Ca) excretion in the urine for disposal, is common among all age groups in the US, including infants. Despite high salt intake, potassium (K) intake is 40% lower than FDA recommendations among children, which may also increase urinary Ca excretion. Elevated 24-hour urine Na/K ratio was identified as an independent risk factor for stones among Italian adults. We investigated the Na/K ratio among our pediatric stone formers. METHODS: A retrospective review of the 24-hour urine samples provided by confirmed pediatric stone formers between 2000 – 2010 was performed. For those with multiple samples, the Na/K ratio was calculated on the first 24-hour urine. The normal pediatric urine Na/K ratio has been defined as ⬍ 2.5. RESULTS: 116 patients with confirmed urolithiasis and complete 24-hour urine stone risk analysis which included Na and K measurements were identified. Of these, 56 (48.3%) were males, and average age was 11.9 (2.7–21) years. The mean Na/K ratio was 4.26 (0.3–12.7). Based on a defined normal Na/K ratio of ⬍ 2.5 in children, 88 (75.9%) had elevated ratios. Comparing patients in the lowest vs. highest quartiles for their Na/K ratios, there were statistically significant differences in 24-hr urinary excretion of Ca (107.4 vs. 164.3 mg/d, p⫽0.02), Na (71.7 vs. 170.1 mEq/d, p⬍0.0001), and K (44.1 vs. 24.4 mEq/d, p⬍0.0001). There were no differences in citrate (387.3 vs. 383.5 mg/d), supersaturation of CaOx (1.8 vs. 2.2), or age (11.6 vs. 8.7 years), p⬎0.05. CONCLUSIONS: Elevated Na/K ratios were identified in ⬎ 75% of our pediatric stone-formers, with average 24-hour urine Na/K ratios nearly double reported normal values. We propose that epidemiologic trends towards excessive dietary salt coupled with low K intake among
THE JOURNAL OF UROLOGY姞
e551
US children may be a risk for pediatric stone disease, and that calculating Na/K ratio might help monitor compliance with the currently recommended dietary interventions on serial urine investigations. Source of Funding: CCRAC grant #2001-5
1382 ARE CHILDREN WITH STONES AT RISK FOR BREAKING BONES? BONE MINERAL DENSITY ANALYSIS IN PEDIATRIC STONE FORMERS Candace Granberg*, Katherine Twombley, Aditya Bagrodia, Khashayar Sakhaee, Naim Maalouf, Linda A. Baker, Nicol C. Bush, Dallas, TX INTRODUCTION AND OBJECTIVES: Adult stone formers are known to have lower bone mineral density (BMD) and higher rates of osteoporotic fractures compared to non-stone formers. Low BMD in children is associated with increased risk of bone fractures. The objective of this study was to evaluate BMD among our pediatric stone patients. METHODS: Retrospective review of all patients undergoing dual-energy x-ray absorptiometry (DXA) scan since 2000 with a confirmed diagnosis of urolithiasis was performed. Immobilized patients were excluded. Z-scores, expressed as number of age- and gendermatched standard deviations from the mean, and 24-hour urine profiles were assessed. Since 2009, patients with ⱖ 1 stone have been prospectively queried about fracture history. Hypercalciuria was defined as Ca/Cr ratio ⬎ 0.2 and/or ⬎ 4 mg/kg/day. Statistical testing was performed with Fisher’s exact and t-test, with p⬍0.05 considered statistically significant. RESULTS: 132 confirmed stone-formers (76F:56M) underwent DXA analysis at average age 12.2 years. Average lumbar and radial forearm BMD Z-scores were ⫺0.8 (range ⫺4.2 to ⫹2.7) and ⫺0.5 (range ⫺2.9 to ⫹2.2), respectively. Lumbar BMD Z-scores were ⬍ ⫺1.0 in 51/127 (40.2%) patients, and ⬍ ⫺2.0 in 21/127 (16.5%). 79 of 132 children have completed 24-hour urine stone risk analysis, demonstrating 45.6% with hypercalciuria. Table 1 stratifies BMD Z-score based on presence or absence of hypercalciuria. Hypercalciuria was not associated with risk of BMD Z-score ⬍ ⫺1 (p⫽0.36). Among 22 stone-formers who were prospectively queried about bone fracture history, 7 (31.8%) had one or more fractures. Average BMD Z-score in those with versus without fractures was ⫺1.1 and ⫺0.7, respectively. CONCLUSIONS: Pediatric stone disease may identify an atrisk population for future osteoporosis and fractures. Over 40% of our pediatric stone formers had Z-scores ⬍ ⫺1.0, a value associated with increased fracture risk in children. Screening DXA scans should be performed in pediatric stone-formers and/or hypercalciurics, particularly in those with a history of fracture. Since adolescence is the period for peak bone mass accrual, it may be the ideal time for dietary and/or medical intervention to decrease future osteoporotic risk. Table 1. DXA results based on presence or absence of hypercalciuria. Nonhypercalciuric Hypercalciuric p-value Total patients (n⫽79) 43 (54.4%) 36 (45.6%) Mean lumbar Z-score (SD)
⫺0.9 (1.08)
⫺1.0 (1.83)
0.76
Z-score ⬍ -1, n (%)
22 (51.2)
14 (38.9)
0.36
Z-score ⬍ -2, n (%)
9 (20.9)
7 (19.4)
1.00
⫺0.2 (1.35)
⫺0.8 (1.46)
Mean radial Z-score (SD)
Source of Funding: CCRAC grant #2001-5
0
form Infrared Spectroscopy (FTIR). Logistic regression analyses were performed to determine differences in the incidence of components based on age, gender and geographic location. For geographic analyses, the United States was divided into regions based on climate (North, South, Midwest, Mountain West and West). RESULTS: A total of 5,245 stones analyses were included in our study, with all 50 states being represented. 44% of stones were submitted from male patients. Calcium was the most common component in both male and female children, being found in 95.6% of stones. Uric acid stones were more common in males (1.4% vs 0.6%, p⬍0.05), while infectious stones were more common in females (4.8% vs 3.8%, p⬍0.05). Stones containing calcium oxalate increased with age (59% 1–5 year olds (yo), 79% 6 –13 yo, 88% 14 –18 yo, p⬍0.05). Stones containing calcium phosphate were more frequent in the youngest age group (75% 1–5 yo, 57% 6 –13 yo, 61% 14 –18 yo, p⬍0.05) and cystine stones were more frequent in younger males (6.1% 1–5 yo, 2.4% 6 –13 yo, 3.5% 14 –18 yo, p⬍0.05). Infectious stones accounted for 4.4% of all stones, and decreased with age (12% 1–5 yo, 6.6% 6 –13 yo, 2.4% 14 –18 yo, p⬍0.05). No significant differences were observed between regions. CONCLUSIONS: This series is the largest stone composition analysis of the U.S. pediatric population to date and the first to represent children nationwide. Our analysis demonstrates age- and genderspecific differences in stone composition. These data indicate stone composition is similar throughout the U.S. and has been consistent over the past several decades. Source of Funding: None
1381 DO PEDIATRIC STONE-FORMERS HAVE A HIGH-SODIUM DIET? ANALYSIS OF 24-HOUR URINE SODIUM/POTASSIUM RATIOS IN PEDIATRIC STONE FORMERS Candace Granberg*, Aditya Bagrodia, Katherine Twombley, Khashayar Sakhaee, Naim Maalouf, Linda A. Baker, Nicol C. Bush, Dallas, TX INTRODUCTION AND OBJECTIVES: Dietary factors may contribute to the rise in pediatric stone disease. Excess sodium (Na) intake, which necessitates calcium (Ca) excretion in the urine for disposal, is common among all age groups in the US, including infants. Despite high salt intake, potassium (K) intake is 40% lower than FDA recommendations among children, which may also increase urinary Ca excretion. Elevated 24-hour urine Na/K ratio was identified as an independent risk factor for stones among Italian adults. We investigated the Na/K ratio among our pediatric stone formers. METHODS: A retrospective review of the 24-hour urine samples provided by confirmed pediatric stone formers between 2000 – 2010 was performed. For those with multiple samples, the Na/K ratio was calculated on the first 24-hour urine. The normal pediatric urine Na/K ratio has been defined as ⬍ 2.5. RESULTS: 116 patients with confirmed urolithiasis and complete 24-hour urine stone risk analysis which included Na and K measurements were identified. Of these, 56 (48.3%) were males, and average age was 11.9 (2.7–21) years. The mean Na/K ratio was 4.26 (0.3–12.7). Based on a defined normal Na/K ratio of ⬍ 2.5 in children, 88 (75.9%) had elevated ratios. Comparing patients in the lowest vs. highest quartiles for their Na/K ratios, there were statistically significant differences in 24-hr urinary excretion of Ca (107.4 vs. 164.3 mg/d, p⫽0.02), Na (71.7 vs. 170.1 mEq/d, p⬍0.0001), and K (44.1 vs. 24.4 mEq/d, p⬍0.0001). There were no differences in citrate (387.3 vs. 383.5 mg/d), supersaturation of CaOx (1.8 vs. 2.2), or age (11.6 vs. 8.7 years), p⬎0.05. CONCLUSIONS: Elevated Na/K ratios were identified in ⬎ 75% of our pediatric stone-formers, with average 24-hour urine Na/K ratios nearly double reported normal values. We propose that epidemiologic trends towards excessive dietary salt coupled with low K intake among
THE JOURNAL OF UROLOGY姞
e551
US children may be a risk for pediatric stone disease, and that calculating Na/K ratio might help monitor compliance with the currently recommended dietary interventions on serial urine investigations. Source of Funding: CCRAC grant #2001-5
1382 ARE CHILDREN WITH STONES AT RISK FOR BREAKING BONES? BONE MINERAL DENSITY ANALYSIS IN PEDIATRIC STONE FORMERS Candace Granberg*, Katherine Twombley, Aditya Bagrodia, Khashayar Sakhaee, Naim Maalouf, Linda A. Baker, Nicol C. Bush, Dallas, TX INTRODUCTION AND OBJECTIVES: Adult stone formers are known to have lower bone mineral density (BMD) and higher rates of osteoporotic fractures compared to non-stone formers. Low BMD in children is associated with increased risk of bone fractures. The objective of this study was to evaluate BMD among our pediatric stone patients. METHODS: Retrospective review of all patients undergoing dual-energy x-ray absorptiometry (DXA) scan since 2000 with a confirmed diagnosis of urolithiasis was performed. Immobilized patients were excluded. Z-scores, expressed as number of age- and gendermatched standard deviations from the mean, and 24-hour urine profiles were assessed. Since 2009, patients with ⱖ 1 stone have been prospectively queried about fracture history. Hypercalciuria was defined as Ca/Cr ratio ⬎ 0.2 and/or ⬎ 4 mg/kg/day. Statistical testing was performed with Fisher’s exact and t-test, with p⬍0.05 considered statistically significant. RESULTS: 132 confirmed stone-formers (76F:56M) underwent DXA analysis at average age 12.2 years. Average lumbar and radial forearm BMD Z-scores were ⫺0.8 (range ⫺4.2 to ⫹2.7) and ⫺0.5 (range ⫺2.9 to ⫹2.2), respectively. Lumbar BMD Z-scores were ⬍ ⫺1.0 in 51/127 (40.2%) patients, and ⬍ ⫺2.0 in 21/127 (16.5%). 79 of 132 children have completed 24-hour urine stone risk analysis, demonstrating 45.6% with hypercalciuria. Table 1 stratifies BMD Z-score based on presence or absence of hypercalciuria. Hypercalciuria was not associated with risk of BMD Z-score ⬍ ⫺1 (p⫽0.36). Among 22 stone-formers who were prospectively queried about bone fracture history, 7 (31.8%) had one or more fractures. Average BMD Z-score in those with versus without fractures was ⫺1.1 and ⫺0.7, respectively. CONCLUSIONS: Pediatric stone disease may identify an atrisk population for future osteoporosis and fractures. Over 40% of our pediatric stone formers had Z-scores ⬍ ⫺1.0, a value associated with increased fracture risk in children. Screening DXA scans should be performed in pediatric stone-formers and/or hypercalciurics, particularly in those with a history of fracture. Since adolescence is the period for peak bone mass accrual, it may be the ideal time for dietary and/or medical intervention to decrease future osteoporotic risk. Table 1. DXA results based on presence or absence of hypercalciuria. Nonhypercalciuric Hypercalciuric p-value Total patients (n⫽79) 43 (54.4%) 36 (45.6%) Mean lumbar Z-score (SD)
⫺0.9 (1.08)
⫺1.0 (1.83)
0.76
Z-score ⬍ -1, n (%)
22 (51.2)
14 (38.9)
0.36
Z-score ⬍ -2, n (%)
9 (20.9)
7 (19.4)
1.00
⫺0.2 (1.35)
⫺0.8 (1.46)
Mean radial Z-score (SD)
Source of Funding: CCRAC grant #2001-5
0