A comparison between an in vitro ureteroscopic stone size estimation and the stone size measurement with the help of a scale on stone baskets

Abstract

This first attempt at validation of a scale on stone baskets shows different results for each basket which could be systematically improved. Until now, the estimation of the surgeons is better than the measurement, but it is also influenced by factors like the surgeon or the color of the stone.

A New Automatically Fixating Stone Basket (2.5 F) Prototype with a Nitinol Spring for Accurate Ureteroscopic Stone Size Measurement

“…The results of our previous study were in line with those of Patel et al [ 6 ] and confirmed that endourologists are able to assess residual stone fragment size accurately enough to make intraoperative decisions about direct extraction or further laser lithotripsy. Conversely, we also showed that it was feasible to measure the stone with the described basket handle scale [ 8 ], which could be especially suitable for junior endourologists; however, improvements regarding the accuracy of this new method were required and a possible solution is provided in the current study. It has been already shown that the visual stone size estimation is biased by multiple factors, such as the color of the stone and the experience of the surgeon [ 8 ].…”

“…Conversely, we also showed that it was feasible to measure the stone with the described basket handle scale [ 8 ], which could be especially suitable for junior endourologists; however, improvements regarding the accuracy of this new method were required and a possible solution is provided in the current study. It has been already shown that the visual stone size estimation is biased by multiple factors, such as the color of the stone and the experience of the surgeon [ 8 ]. Interestingly, a slight tendency to underestimate the size of large stones (> 6 mm) was observed [ 8 ]; therefore, the measurement of these stone sizes could be enhanced with the proposed basket prototype.…”

“…It has been already shown that the visual stone size estimation is biased by multiple factors, such as the color of the stone and the experience of the surgeon [ 8 ]. Interestingly, a slight tendency to underestimate the size of large stones (> 6 mm) was observed [ 8 ]; therefore, the measurement of these stone sizes could be enhanced with the proposed basket prototype.…”

“…A standard handle (Urotech ® ) connected to a 2.5-F basket was described previously [ 7 , 8 ] and was used in this prototype. It was developed in cooperation with Prof. S. Lahme (Pforzheim, Germany).…”

“…The nonlinear millimeter basket scale was compared in vitro with the visual estimation of two surgeons, and manual stone measurement was used as the reference method. The 2.5-F nitinol basket was the most accurate for measuring larger stones (> 6 mm) with sensitivity of 56% and specificity of 84%, while the 4.0-F basket was the most accurate for smaller stones (< 3 mm); however, the study showed that the visual ureteroscopic estimation was superior to the basket measurement [ 8 ]. The basket system could have been inferior to visual assessment as a result of a mismatch between the steel spring and the nitinol basket, which may have influenced the measurement accuracy depicted on the scale.…”