Login to Access Video or Poster Abstract: MP90-14
Sources of Funding: None

Introduction

Equil 2 has been the gold standard for estimation of urinary saturation of stone-forming salts (relative saturation ratio, RSR). The Joint Expert Speciation System (JESS) is an alternative, perhaps superior, computer program that takes into account soluble complexes that Equil 2 does not and is thought to be a more accurate estimation of supersaturation (saturation index, SI). While RSR is often provided in 24-hour urine analyses, the clinically relevant impact of these estimations of supersaturation on stone activity is not well studied. Our goal was to determine if SI CaOx correlates with stone activity in calcium oxalate (CaOx) stone formers.

Methods

We reviewed the charts of 604 patients from our stone clinic between 2005 and 2016 and identified CaOx stone formers who had a baseline 24-hour urine collection and at last one follow-up urine collection after the initiation of drug and/or dietary therapy. Patient demographics, imaging studies, serum chemistries, and 24-hour urine studies were recorded in a timeline for each patient. SI was calculated using JESS for each 24-hour urine study. Stone recurrence (SR) was defined as stone growth or new stone formation and no recurrence (NR) indicated no new stone formation. Absolute SI values were compared between times of SR and times of NR, and change in SI from baseline to time of SR were correlated with SI. Statistical analysis was performed with SAS, and significance was set at p<0.05.

Results

In total, 255 patients with 358 events were included in the analysis. Mean patient age was 51 ± 13 SD years, with a male:female ratio of 1.3. Comparing NR (98 patients with 97 events) to SR (157 patients with 113) demonstrated no significant difference in mean SI CaOx values (5.6 ± 2.8 versus 5.6 ± 2.9, p=0.6). In addition, in patients who experienced SR (n=157) no significant difference was seen comparing mean SI CaOx values during NR (n=148) or SR (n=113) events (5.9 ± 2.8 versus 5.6 ± 2.9, respectively, p=0.08). For all patients with SR, 65 were identified who experienced both changes from SR to NR (median δSI CaOx 0.20, IQR -1.46-1.21) and NR to SR (median δSI CaOx 0.52, IQR -1.55-1.47). No significant difference was seen (p=0.84).

Conclusions

At first evaluation, neither absolute nor change in SI correlates with stone recurrence and may not be a reliable way to follow effectiveness of medical therapy.

Funding

None