2226 A NOVEL CONCEPTUAL MODEL FOR INDIVIDUALIZED GOAL URINE VOLUME TO PREVENT STONE RECURRENCE

Abstract

You have accessJournal of UrologyStone Disease: Evaluation & Medical Management1 Apr 20112226 A NOVEL CONCEPTUAL MODEL FOR INDIVIDUALIZED GOAL URINE VOLUME TO PREVENT STONE RECURRENCE Mark D. Sawyer, Davis P. Viprakasit, S. Duke Herrell, and Nicole L. Miller Mark D. SawyerMark D. Sawyer Nashville, TN More articles by this author , Davis P. ViprakasitDavis P. Viprakasit Nashville, TN More articles by this author , S. Duke HerrellS. Duke Herrell Nashville, TN More articles by this author , and Nicole L. MillerNicole L. Miller Nashville, TN More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2467AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Stone formers are instructed to produce at least 2 liters (2L) of urine/day. Current recommendations do not account for individual factors, e.g. patient size. The goal of this study is to determine if an appropriate individualized goal urine volume (V) could be determined and compared to a 2L goal. METHODS Our hypothesis was that body weight, ideal body weight, age and gender would directly influence and therefore predict daily calcium excretion (Ca24) with an a priori linear regression model. A database of initial 24 hour urine studies (with appropriate 24h creatinine) performed through Litholink (Chicago, IL) was established. Explanatory variables used to predict Ca24 were age, gender, weight and height. To minimize inappropriate covariance, height was used as a surrogate for ideal body weight and BMI was excluded. An “average” hypothetical index patient (70kg, 168cm, 45 year old man) was used to determine goal urine calcium concentration. Goal calcium concentration, [Ca], was obtained by dividing predicted Ca24 by current goal V=2L and was nearly 2.5 mmol/L. Individual goal V was determined based on projected Ca24 and this goal [Ca]. Using measured values, the two models of goal V were then used to determine anticipated [Ca] and [oxalate] and the [Ca]*[oxalate] product (supersaturation proxy) if patients adjusted urine output to respective goals. Assumed was a static model (i.e. Ca24 did not change with urine volume). RESULTS This study included 194 patients (M=96; F=98; age 18–78). In the regression, weight was significant (p < 10−6). Comparing our model with a 2L goal, the mean values improved for projected [Ca] (2.92 to 2.51 mmol/L), [oxalate] (0.22 to 0.19 mmol/L) and [Ca]*[oxalate] product (0.62 to 0.46 mmol2/L2). Derived individualized goal V in this cohort ranged from 1.1 L (32kg, 127cm F) to 4.2 L (150kg, 188cm M) (median=2.3 L). Range of expected volume as a percentage of body weight narrowed considerably: 1.3–6.3% (2L goal) to 2.7–3.4% (model). CONCLUSIONS If our model and approach is validated, then current recommendations could: overburden small patients; undertreat obese patients; and become obsolete with increasing obesity rates. An individualized approach to urine volume could improve expected outcomes. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e893 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mark D. Sawyer Nashville, TN More articles by this author Davis P. Viprakasit Nashville, TN More articles by this author S. Duke Herrell Nashville, TN More articles by this author Nicole L. Miller Nashville, TN More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...