The Urine Specific Gravity Dipstick: A Useful Tool to Increase Fluid Intake in Stone Forming Patients

Abstract

High fluid intake is the only preventive dietary measure that can be recommended to all patients with stones. However, the efficacy of dietary advice given to patients is unknown. We compared the impact of dietary advice to increase hydration (group 1, 57 patients) and of no dietary advice (group 2, 83 patients) on 24-hour urine volume. No significant difference was noted between groups 1 (1,624 ml.) and 2 (1,732 ml.). We then determined if urine specific gravity dipsticks could help patients increase the 24-hour urine volume. A correlation between 24-hour urine volume and mean urine specific gravity was performed on 263 randomly chosen patients. There was an inverse relationship between urine specific gravity and 24-hour urine volume with a correlation coefficient of 0.522 (y = 1.0207 - 0.00374x). Most patients (81.6%) with 24-hour urine volumes of less than 2.1 had a urine specific gravity of more than 1.010. The use of specific gravity dipsticks was evaluated as a tool to help 24 patients increase the 24-hour urine volume. The 24-hour urine volume increased significantly (p less than 0.05, paired Student's t test) in patients after feedback from specific gravity dipsticks when they were instructed to keep the urine specific gravity at or less than 1.010 (average 24-hour urine volume increased 192%). We conclude that dietary advice may be insufficient to modify fluid intake habits in stone patients. However, modifications of fluid intake habits may be improved by feedback from specific gravity dipsticks.

A Case for Water in the Treatment of Polycystic Kidney Disease

“…For example, assuming a daily osmolar excretion of 750 or 1000 mosm, 3 or 4 L of urine, respectively, would yield a mean osmolality of 250 mosm/kg H 2 O (specific gravity approximately 1008). The use of dipsticks for measuring specific gravity may help patients reach this goal (81). If the daily fluid intake was evenly spaced, the mean plasma AVP level would decrease proportionately with the mean U osm .…”

Urine specific gravity and water hardness in relation to urolithiasis in persons with spinal cord injury

“…As advocated in the general population, 8 using the test dispstick to monitor speci®c gravity as a self-feedback tool for modifying¯uid intake and improving hydration status would be a simple, inexpensive, and risk-free strategy for the prevention of stone occurrence and recurrence. The ecacy of this intervention on stone prophylaxis merits further trials.…”

“…This self-feedback method seems feasible because it is simple, quick, inexpensive, and valid with a high correlation with urine osmolality (r40.9) 16 and total 24-h urine volume (r=70.5). 8 Hardness is caused primarily by compounds of calcium and magnesium and by a variety of other metals. Increased dietary calcium intake has been reported to decrease stone incidence in the general population.…”

“…7 The use of urine speci®c gravity test strips as a self-feedback tool has been shown to be more successful in increasing¯uid intake than a simple dietary instruction. 8 However, the in¯uence of urine speci®c gravity on stone formation has never been examined.…”

“…According to a prior investigation, speci®c gravity at or less than 1.010 was estimated to be equivalent to a total daily urine output of two liters or more; speci®c gravity greater than 1.017 was estimated to be approximately equal to urine volume less than one liter per day. 8 We therefore classi®ed speci®c gravity into these three levels. …”