Can 24-Hour Urine Stone Risk Profiles Predict Urinary Stone Composition?

Abstract

Distinguishing uric acid from calcium oxalate stones can be performed with relative accuracy using parameters from the 24-hour urine stone risk profile and the patient's BMI and age.

Nomogram to predict uric acid kidney stones based on patient’s age, BMI and 24-hour urine profiles: a multi-center validation

“…We searched for patients with kidney stones who had stone composition analysis and 24-hour urine collection within 6 months of each other from January 2010 to December 2013. Patients who were part of the initial construct of the nomogram 6 were excluded from this study. Kidney stones were obtained from surgi-nomogram to predict uric acid kidney stones cal procedures for stone removal or after spontaneous passage.…”

“…For each patient, these six variables were applied to a previous published nomogram (Fig. 1), 6 which has the capability of predicting uric acid over calcium stones. When using the nomogram, one should locate their patient's age and draw a line straight up to find the corresponding points score.…”

“…Urinary pH was also recorded, although it was not applied to the nomogram, as our prior study demonstrated that pH did not contribute significantly to the predictive value of the nomogram. 6 For each population, patients were divided in two groups: uric acid versus calcium stones and then compared for demographic data, urinary parameters, and total points. Thereafter, nomogram sensitivity, specificity, and accuracy were tested.…”

“…[3][4][5] Furthermore, 24-hour urine analyses have demonstrated that uric acid stone formers have a higher excretion of urinary sodium and a lower excretion of urinary calcium and oxalate when compared to calcium stone formers. 6 Imaging exams are also helpful when trying to distinguish between uric acid and calcium stones. Single-and dualenergy computed tomography (CT) scans have demonstrated promising results; 7 however, protocols for imaging acquisition and interpretation are not available in most of hospitals yet, thus preventing widespread use of this technology.…”

“…6 This nomogram can guide medical decisions using select variables and minimizing the need for CT imaging, with its inherent cost and radiation exposure, as the nomogram does not include stone density (Hounsfield Units).…”