Login to Access Video or Poster Abstract: MP90-08
Sources of Funding: None

Introduction

Current American Urological Association (AUA) guidelines do not discuss recommendations in obtaining a stone analysis when a bilateral stone procedure is performed. To date, there is a limited amount of data surrounding discordant stone analysis when performing a simultaneous bilateral stone procedure. Stone analysis results, as well as 24-hour urinalysis are utilized for the medical management of stone disease and could possibly be misrepresented if conflicting stone analysis results were present. Therefore, we aim to describe the rate of discordant stone analysis results in patients undergoing ureteroscopy.

Methods

A retrospective chart review was performed for all patients undergoing bilateral ureteroscopy with stone removal by a single surgeon at a single hospital between 2013 and 2016. All stones were analyzed at a single stone analysis laboratory using Fourier transform infrared spectroscopy (Beck labs, Indianapolis IN). Stones were then classified unilaterally based upon the dominant present (>50%). The only exception was for brushite where the presence of any brushite led to classification as a brushite stone former. 24-hour urinalysis results were reviewed and statistical analysis performed comparing discordant and concordant patient populations, assessing significant differences that would influence clinical management.

Results

We identified 89 patients (178 renal units) who had bilateral stones removed at the time of ureteroscopy. The majority of stones were classified as calcium oxalate (CaOx) (59.4%) followed by CaP (30.6%), uric acid (UA) (3.9%), brushite (3.9%) and cystine (2.2%). Discrepancies in stone classifications were present 22% of the time. Evaluation of 24-hour urinalysis results demonstrated striking differences between those with conflicting and similar stone analysis results. Those patients with CaOx:CaP stone discordance compared to CaOx:CaOx concordant stone formers were more likely to have an elevated pH (p<0.001), calcium phosphate supersaturation (p<0.01) and lower uric acid supersaturation (p=0.02).

Conclusions

Discrepancies in stone classifications are common in patients with bilateral stone disease. When metabolic evaluation was performed in these patients there were significant differences between discordant and concordant groups, especially CaOx only and CaOx:CaP stone formers. Thus, a single stone analysis in the setting of bilateral stone disease is insufficient and may lead to mismanagement when it is utilized in addition to 24-hour urinalysis results.

Funding

None