Publication: Association between hounsfield unit density and stone size with stone free status post ureteroscopy lithotripsy
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Date
2022
Authors
Samsudin, Shazatul Ezanni
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Abstract
Background: Ureteroscopy lithotripsy (URSL) is an essential treatment modality for ureteral stones that is currently used for stones of all sizes, present at any location within the ureter. It is well established that stone size and its HU value are the main factors that influence the success of other type of surgery in patient with nephrolithiasis such as ESWL and PCNL. HU value is a convenient radiographic measurement that correlated well with the stone chemical composition. Given the effectiveness of predicting stone composition and determining its size preoperatively using plain CT KUB, it may play a role in the selection of treatment by the surgeon. A CT-based predictive model using these factors could enable estimation of the stone-free rate after URSL in individual patients and thus facilitate treatment planning. The purpose of this study is to evaluate the association between HU density and stone size with operative time and stone free status. Methods: This is a retrospective cohort study and was conducted in Hospital USM, Kota Bharu, Kelantan, Malaysia. A total of 204 patients who underwent elective URSL in Hospital USM and was diagnosed with a single ureteric stone in preoperative plain CT KUB prior to the surgery were identified and enrolled in this study. HU density and stone size were measured from PACS database. Plain KUB radiograph on post operative day 1 will be reviewed to look for any residual stone or complete stone clearance. The association between HU density and stone size with operative time and stone free status had been carried out using Pearson's correlation coefficient test. Results: A total of 204 patients underwent elective URSL for a single ureteric stone. About 86% (n=176 patient) of the patient had a successful URSL with stone free status on post operative day 1. Mean age of the patient regardless of gender was 53.7-year-old (± 14.862-year-old). Mean stone size measures 13.086mm (± 5.568mm). Mean HU value of the ureteric stone with successful fragmentation was 886.114HU (± 347.416HU) with mean HU density of 78.996 HU/mm (± 44.944 HU/mm). Mean URSL operative time was 1.156-hour (± 0.052) A statistically significant correlation between HU density and operative time noted with p value of 0.047. However, there is no significant correlation seen between stone size and operative time.(p=0.084), HU density with stone free status (p=0.391) and stone size with stone free status (p=0.438). Conclusion: Composition of a ureteric stone being represented by HU value are the cornerstone in URSL success. Our study shows that there is statistically significant negative correlation of URSL operative times with HU density of calculi. Patients with higher HU density were expected to have shorter URSL operative time. Thus, the HU density measurement may give extra information to the managing team in making future decisions on mode of surgery and patient counselling, especially where multiple treatment options might apply.
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Keywords
ureteric stone , ureteroscopy lithotripsy