Prediction of calcium oxalate monohydrate stone composition during ureteroscopy

Reza Hamidizedah; Megan Melnyk; Joel M. H. Teichman

doi:10.1117/12.905675

9 February 2012 Prediction of calcium oxalate monohydrate stone composition during ureteroscopy

Reza Hamidizedah, Megan Melnyk, Joel M. H. Teichman

Proceedings Volume 8207, Photonic Therapeutics and Diagnostics VIII; 82071F (2012) https://doi.org/10.1117/12.905675
Event: SPIE BiOS, 2012, San Francisco, California, United States

Abstract

Introduction: Prior research shows that Ho:YAG lithotripsy produces tiny dust fragments at low pulse energy (0.2J). However, calcium oxalate monohydrate (COM) stones may not fragment at this low pulse energy setting. Stone composition is rarely known until after surgery and historically, attempts to predict stone composition on the basis of endoscopic stone appearance were unsuccessful. Current endoscopic technology permits visual details that previously were not evident. As COM appears black under ambient light, we attempt to predict COM stone composition at the time of ureteroscopy based on its endoscopic appearance. Methods: Consecutive subjects undergoing ureteroscopy for stone disease were studied. Any portion of the stone that appeared black under endoscopic vision was considered clinical evidence of COM. Predicted stone composition was correlated with post-operative calculus analysis. Results: 46 consecutive ureteroscopic stone cases were analyzed prospectively. 25 of 28 subjects (89%) with black stones had stones later proven to be COM by composition analysis, versus one of 18 patients (6%) with non-black stones that were COM (p<0.0001). A black endoscopic stone appearance had a positive predictive value for COM of 89% and a non-black endoscopic stone appearance had a negative predictive value for COM of 94% (sensitivity 96%, specificity 83%). Conclusions: COM may reasonably be predicted intra-operatively by its black endoscopic appearance. The clinical utility would be to use higher laser pulse energy settings than for non-COM compositions. This data raises the possibility that more sophisticated optical characterization of endoscopic stone appearance may prove to be a useful tool to predict stone composition.

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Reza Hamidizedah, Megan Melnyk, and Joel M. H. Teichman "Prediction of calcium oxalate monohydrate stone composition during ureteroscopy", Proc. SPIE 8207, Photonic Therapeutics and Diagnostics VIII, 82071F (9 February 2012); https://doi.org/10.1117/12.905675

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KEYWORDS

Endoscopy

Calculi

Calculus

Calcium

Pulsed laser operation

Statistical analysis

Surgery

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