Endourology & Stone Disease(구연) (E-155)

Using Hounsfield unit (HU) - volume models of kidney stones to predict successful stone dusting during retrograde intra-renal surgery (RIRS)
Department of Urology, Kyung Hee University, School of Medicine
¹Department of Radiology, Kyung Hee University, School of Medicine
Dong Soo Kim, Seung Hyun Jeon, Sun-Ju Lee, Choong Hyun Lee, Sung-Goo Chang, Sung Kyoung Moon¹, Joo Won Lim¹, Sang Hyub Lee
Introduction
Computer tomography (CT) with Hounsfield unit (HU) measurement is commonly used to evaluate renal stones. We drew histogram models depicting the volume of a stone’s entire HUs and analyzed relevant parameters to predict the success of renal stone dusting.
Material and Methods
The medical records of 80 patients who underwent evaluation for renal stones from January 2018 to January 2019 at Kyung Hee University Hospital were initially reviewed. Among them, 49 patients with 55 stones who ultimately underwent retrograde intra-renal surgery (RIRS) were analyzed. We drew histograms representing the volume of HUs in each stone. Maximal HU, minimal HU, difference in maximal-minimal HU, HU standard deviation, total stone volume, stone volume of maximal HU and success of dusting (Energy 0.2-0.4 J, Frequency > 50 Hz) were evaluated.
Results
Among the total 55 stones, 32 were successfully dusted and 23 were fragmented. Dusted stones showed a more homogenous distribution of HU while fragmented stones were more concentrated. Dusted stones had higher mean difference in maximal-minimal HU (1102.94 ± 376.63 vs 794.91 ± 415.05, p = 0.0073) and higher HU standard deviation (262.73 ± 112.61 vs 155.65 ± 95.69). Stones that were fragmented had larger volume of peak HU (4.52 ± 2.53 vs 13.28 ± 8.10, p < 0.0001) and larger stone volume. (0.72 ± 0.66 vs 1.98 ± 1.66, p = 0.0003) Cut off values for successful dusting was evaluated using a classification and regression tree. Dusting was successful when the stone volume of maximal HU was < 8.9mm³. Among them, stones with a difference in maximal-minimal HU of > 853 were dusted. Also, stones with mean HU < 355 could be dusted (p = < 0.0001).
Conclusion
Even in larger stones, those with smaller volume of maximal HU, larger difference in maximal-minimal HU, and smaller mean HU were eligible for dusting. Pre-operative evaluation with HU histograms can help decide whether to choose an endoscopic approach in large stones.
keywords : Computer tomography, Hounsfield unit, dusting

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