1556 SPOT SPECIFIC GRAVITY MEASURES PREDICT 24-H URINE VOLUMES: A NEW CLINICAL TOOL FOR BIOFEEDBACK IN MEETING VOLUME RECOMMENDATIONS

Abstract

You have accessJournal of UrologyStone Disease: New Technology1 Apr 20131556 SPOT SPECIFIC GRAVITY MEASURES PREDICT 24-H URINE VOLUMES: A NEW CLINICAL TOOL FOR BIOFEEDBACK IN MEETING VOLUME RECOMMENDATIONS Kristina L Penniston, Roy A Jhagroo, and Stephen Y Nakada Kristina L PennistonKristina L Penniston Madison, WI More articles by this author , Roy A JhagrooRoy A Jhagroo Madison, WI More articles by this author , and Stephen Y NakadaStephen Y Nakada Madison, WI More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.3066AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Urine supersaturation is a driving factor in renal crystal formation/growth. Urine supersaturation is highly dependent on volume, yet many patients cannot consistently achieve >2 L/d. Fluid intake is highly predictive of output. There is a disconnect in some patients between what they perceive to be adequate intake and their urine output. We investigated the efficacy of specific gravity (SG) as a patient education and biofeedback tool to estimate 24-h urine volume (UV). METHODS Healthy individuals (n=7) from our medical and research staff were recruited and trained to use both a urine dipstick (Siemens, Tarrytown, NY) and a hand-held hydrometer (Pet Smart, Madison, WI), used in measuring salinity of aquatic habitats. Using both instruments, subjects were asked to record SG measures of their urine at first collection of the day, within 1 h of both the mid-day and evening meals, and at bedtime. UV at each void was recorded and summed to obtain 24-h UV. Individuals were grouped into low-volume (LV, <2 L/d) and high-volume (HV, >2 L/d) groups. Data from a total of 13 days were evaluated. RESULTS 24-h UVs ranging from 1000-3150 mL were obtained. Mean SG for each day correlated inversely with 24-h UV and was different (p=0.03 for hydrometer and p=0.007 for dipstick) between groups. The mean SG measure for the HV group did not exceed 1.020 at 75% (3 of 4) of the daily measurement points whereas the SG for the LV group exceeded 1.025 at both the first-morning and bedtime collections. Moreover, mean SG never went below 1.015 for those in the LV group but was below that at 3 of 4 timepoints for those in the HV group. SG measures obtained from urine dipstick and hydrometer were highly correlated (R=0.79) and were independent of urine volumes at each measurement point. Subjective reports from subjects indicate the dipsticks are easy to use but are more difficult to interpret than the hydrometers, which have visible unit markings. The dipsticks require visually matching the color obtained with 1 of 7 color gradations on the bottle label; color differences appear subtle to some. CONCLUSIONS SG measured at specific time points during a 24-h period predicts total UV. SG <1.020 predicts a 24-h UV of >2 L. Providing hydrometers or dipsticks to patients, along with instructions for accurate reading of results, may be used as biofeedback to help them gauge how well they are doing regarding the fluid intake required to reach the target daily UV. SG measures between regularly scheduled clinic visits may also provide clinically relevant information about variations in patients' stone risks. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e639 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Kristina L Penniston Madison, WI More articles by this author Roy A Jhagroo Madison, WI More articles by this author Stephen Y Nakada Madison, WI More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...