WCE 2017: Accuracy of Predicting Stone Composition During Endoscopic Evaluation 

Vancouver, Canada (UroToday.com) Jennifer Robles, endourology fellow from Vanderbilt University, presented data that assessed the accuracy of endoscopic evaluation for predicting stone composition intra-operatively. As an introduction to her talk, Dr. Robles explained how predicting stone composition post-operatively has helped direct their management of stone disease. However, they feel knowing the stone composition intra-operatively may help direct both their surgical and medical management.  

A total of 146 patients underwent a retrospective chart review by a single experienced Endourologist to evaluate operative reports, stone analyses, and medical history. They excluded cystine stone formers and determined predominant stone type based on a stone component comprising greater than 50% of the specimen. 

Comparing correct versus incorrect stone composition predictions, the demographics between the two groups had no significant differences. Focusing on what the actual stone compositions were, their stone predictions were very accurate for all stone types (Calcium = 92%, Uric Acid = 98%, Infectious = 94%). Looking at the stones that were incorrectly predicted, half of them were calcium phosphate stones. Eight of the nine calcium stones that were incorrectly predicted to be infectious contained a phosphate component. These nine patients were also more likely to have recurrent urinary tract infections (UTI) or a bowel augmentation.  

In conclusion, Dr. Robles and her team felt endoscopic evaluation can predict stone composition with high accuracy and intra-operative prediction of stone composition can help with their surgical and medical management of stone disease. Incorrect prediction most commonly occurred for infectious stones with phosphate components for patients with more risk factors. 

Presented by: Jennifer Robles

Authors: Tracy Marien, Annie Darves-Bornoz, Jennifer Robles, Nicole Miller 
Affiliation: Vanderbilt University Medical Center, Nashville, TN  

 Written by: Cyrus Lin, Department of Urology, University of California-Irvine at 35th World Congress of Endourology – September 12-16, 2017, Vancouver, Canada