Ho Won Kang1,2, Sung Pil Seo1,2, Yun-Sok Ha3, Won Tae Kim1,2, Yong-June Kim1,2, Seok-Joong Yun1,2, Wun-Jae Kim1,2, Sang-Cheol Lee4,5. 1. Department of Urology, College of Medicine and Institute for Tumor Research, Chungbuk National University, 776 1sunhwan-ro, Seowon-gu, Cheonju, 28644, Korea. 2. Department of Urology, Chungbuk National University Hospital, Cheongju, Korea. 3. Department of Urology, School of Medicine, Kyungpook National University, Daegu, Korea. 4. Department of Urology, College of Medicine and Institute for Tumor Research, Chungbuk National University, 776 1sunhwan-ro, Seowon-gu, Cheonju, 28644, Korea. lscuro@chungbuk.ac.kr. 5. Department of Urology, Chungbuk National University Hospital, Cheongju, Korea. lscuro@chungbuk.ac.kr.
Abstract
PURPOSE: To determine the value of 24-h urine osmolality (UOsm) as a representative index of adequate hydration and predictor of stone recurrence in patients with urolithiasis. METHODS: Medical records of consecutive patients presenting with renal or ureteric stones between 1994 and 2017 were retrospectively reviewed. Patients were grouped according to the results of 24-h UOsm (low ≤ 564 mOsm/kg H2O, high > 564 mOsm/kg H2O). Metabolic parameters and risk of stone recurrence were compared between the two groups. RESULTS: The low urine concentration group were more likely to be older, to be female, and to have a lower body mass index and higher glomerular filtration rate than the high concentration group (each P < 0.005). A positive correlation was seen between 24-h UOsm and urinary calcium, sodium, uric acid, and magnesium excretion and 24-h specific gravity; a negative correlation was seen with 24-h urine volume. Stone-forming constituents, such as calcium and uric acid, were significantly higher in the high urine concentration group. Kaplan-Meier estimates showed that the low urine concentration group had a significantly longer stone recurrence-free period than the high urine concentration group (log-rank test, P < 0.001). In multivariate Cox regression analyses, 24-h UOsm was seen to be an independent risk factor for stone recurrence. CONCLUSIONS: UOsm is a promising approach to assessing hydration and predicting stone recurrence in patients with urolithiasis. Maintaining UOsm < 564 mOsm/kg H2O may reduce the risk of stone recurrence.
PURPOSE: To determine the value of 24-h urine osmolality (UOsm) as a representative index of adequate hydration and predictor of stone recurrence in patients with urolithiasis. METHODS: Medical records of consecutive patients presenting with renal or ureteric stones between 1994 and 2017 were retrospectively reviewed. Patients were grouped according to the results of 24-h UOsm (low ≤ 564 mOsm/kg H2O, high > 564 mOsm/kg H2O). Metabolic parameters and risk of stone recurrence were compared between the two groups. RESULTS: The low urine concentration group were more likely to be older, to be female, and to have a lower body mass index and higher glomerular filtration rate than the high concentration group (each P < 0.005). A positive correlation was seen between 24-h UOsm and urinary calcium, sodium, uric acid, and magnesium excretion and 24-h specific gravity; a negative correlation was seen with 24-h urine volume. Stone-forming constituents, such as calcium and uric acid, were significantly higher in the high urine concentration group. Kaplan-Meier estimates showed that the low urine concentration group had a significantly longer stone recurrence-free period than the high urine concentration group (log-rank test, P < 0.001). In multivariate Cox regression analyses, 24-h UOsm was seen to be an independent risk factor for stone recurrence. CONCLUSIONS: UOsm is a promising approach to assessing hydration and predicting stone recurrence in patients with urolithiasis. Maintaining UOsm < 564 mOsm/kg H2O may reduce the risk of stone recurrence.