CT visible internal stone structure, but not Hounsfield unit value, of calcium oxalate monohydrate (COM) calculi predicts lithotripsy fragility in vitro

Abstract

COM stones are often resistant to breakage using shock wave (SW) lithotripsy. It would be useful to identify by computed tomography (CT) those COM stones that are susceptible to SW's. For this study, 47 COM stones (4-10 mm in diameter) were scanned with micro CT to verify composition and also for assessment of heterogeneity (presence of pronounced lobulation, voids, or apatite inclusions) by blinded observers. Stones were then placed in water and scanned using 64-channel helical CT. As with micro CT, heterogeneity was assessed by blinded observers, using high-bone viewing windows. Then stones were broken in a lithotripter (Dornier Doli-50) over 2 mm mesh, and SW's counted. Results showed that classification of stones using micro CT was highly repeatable among observers (κ=0.81), and also predictive of stone fragility. Stones graded as homogeneous required 1874±821 SW/g for comminution, while stones with visible structure required half as many SW/g, 912±678. Similarly, when stones were graded by appearance on helical CT, classification was repeatable (κ=0.40), and homogeneous stones required more SW's for comminution than did heterogeneous stones (1702±993 SW/g, compared to 907±773). Stone fragility normalized to stone size did not correlate with Hounsfield units (p=0.85). In conclusion, COM stones of homogeneous structure require almost twice as many SW's to comminute than stones of similar mineral composition that exhibit internal structural features that are visible by CT. This suggests that stone fragility in patients could be predicted using pre-treatment CT imaging. The findings also show that Hounsfield unit values of COM stones did not correlate with stone fragility. Thus, it is stone

Predicting the mineral composition of ureteral stone using non-contrast computed tomography

“…However, our study focused on objective criteria, so we did not check the visibility of each stone [23]. In summary, CT density of ureteral stones can predict whether they contain a calcium component, yet cannot predict the mineral composition of calcium-containing stones with a calcium component.…”

Predictive Value of Attenuation Coefficients Measured as Hounsfield Units on Noncontrast Computed Tomography During Flexible Ureteroscopy with Holmium Laser Lithotripsy: A Single-Center Experience

“…[1][2][3] In such an era, the role of Hounsfield units (HUs) on noncontrast CT (NCCT) has been anticipated to decrease, because it is unable to provide any other relevant information, such as internal features. 4,5 Many previous reports, however, indicate that the efficacy of extracorporeal shockwave lithotripsy (SWL) is dependent on target attenuation coefficients on NCCT. [6][7][8] In vitro studies suggest that the attenuation coefficients of calculi measured in HUs on NCCT may predict the ability to fragment urinary stones.…”

The Need for Better Decision Tools in Managing Stone Disease

“…It was previously demonstrated that the internal stone structure visible on CT has a predictive effect for stones composed of calcium oxalate monohydrate as well as those composed of cystine. 6,7 In this issue of The Journal Williams et al (page 996) built on this important work, now addressing the question of whether brushite stones demonstrate the same correlation between CT visible stone structure and stone fragility. 8 In contradistinction to what this investigative group found with cystine and calcium oxalate monohydrate stones, the internal structure of brushite stones did not help identify stones that would fragment more or less readily.…”