Zarse, C. A. et al. CT visible internal stone structure, but not Hounsfield unit value, of calcium oxalate monohydrate (COM) calculi predicts lithotripsy fragility in vitro. Urol. Res. 35, 201-206

Department of Anatomy and Cell Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA.
Urological Research (Impact Factor: 1.39). 09/2007; 35(4):201-6. DOI: 10.1007/s00240-007-0104-6
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Calcium oxalate monohydrate (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 (kappa = 0.81), and also predictive of stone fragility. Stones graded as homogeneous required 1,874 +/- 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 (kappa = 0.40), and homogeneous stones required more SW's for comminution than did heterogeneous stones (1,702 +/- 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 morphology, rather than X-ray attenuation, which correlates with fragility to SW's in this common stone type.

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    • "The latter group of patients was found to have stones that were amenable to medical treatment as opposed to the lithotripsyresistant calculi with homogenous internal architecture. The authors go on to suggest that pretreatment CT can be used to assess calculus fragility and that it is stone morphology, rather than X-ray attenuation, that better correlates with overall fragility [49] "
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    ABSTRACT: Objective. To critically evaluate the current literature in an effort to establish the current role of radiologic imaging, advances in computed tomography (CT) and standard film radiography in the diagnosis, and characterization of urinary tract calculi. Conclusion. CT has a valuable role when utilized prudently during surveillance of patients following endourological therapy. In this paper, we outline the basic principles relating to the effects of exposure to ionizing radiation as a result of CT scanning. We discuss the current developments in low-dose CT technology, which have resulted in significant reductions in CT radiation doses (to approximately one-third of what they were a decade ago) while preserving image quality. Finally, we will discuss an important recent development now commercially available on the latest generation of CT scanners, namely, dual energy imaging, which is showing promise in urinary tract imaging as a means of characterizing the composition of urinary tract calculi.
    Advances in Urology 08/2012; 2012:606754. DOI:10.1155/2012/606754
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    ABSTRACT: Cystine stones are often highly resistant to shock wave lithotripsy (SWL), but it has been reported that cystine stones of "rough" morphology are actually quite susceptible to SWL. Based on the observation that rough cystine stones contain void regions that are visible by helical computed tomographic (CT) imaging, we hypothesized that the internal structure of cystine stones would correlate with the susceptibility of stones to SWL. Cystine stones with average diameters between 4 and 7 mm were scanned using micro and helical CT, classified morphologically according to published criteria, and broken in a research electrohydraulic lithotripter, with fragments sieved through a 2 mm mesh every 50 SWs. Stones with regions of low X-ray attenuation visible on helical CT required only 650 +/- 312 SW/g for total comminution, while those that did not show CT-visible internal structure required 1,046 +/- 307 SW/g (mean +/- SD, P < 0.004). In addition, both average and minimum values for CT number (in Hounsfield units, HU) correlated with SW/g to comminution (P < 0.003 and P < 0.0003, respectively), and these relationships were independent of stone size. This study also confirmed the relationship between the morphological criteria of Bhatta et al. (J Urol 142:937-940, 1989) and cystine stone fragility: Rough stones required 609 +/- 244 SW/g (n = 11), smooth stones 1,109 +/- 308 SW/g (n = 8), and stones intermediate in morphology 869 +/- 384 SW/g (n = 7; rough different from smooth, P < 0.005). In conclusion, cystine stones that appeared homogeneous by helical CT required 61% more SWs for comminution than did stones showing regions of low X-ray attenuation. These findings demonstrate the feasibility of using helical CT to identify cystine stones that will be susceptible to SWL.
    Urological Research 01/2008; 35(6):319-24. DOI:10.1007/s00240-007-0117-1 · 1.39 Impact Factor
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    ABSTRACT: Shock wave lithotripsy (SWL) has proven to be a highly effective treatment for the removal of kidney stones. Shock waves (SWs) can be used to break most stone types, and because lithotripsy is the only noninvasive treatment for urinary stones, SWL is particularly attractive. On the downside SWL can cause vascular trauma to the kidney and surrounding organs. This acute SW damage can be severe, can lead to scarring with a permanent loss of functional renal volume, and has been linked to potentially serious long-term adverse effects. A recent retrospective study linking lithotripsy to the development of diabetes mellitus has further focused attention on the possibility that SWL may lead to life-altering chronic effects. Thus, it appears that what was once considered to be an entirely safe means to eliminate renal stones can elicit potentially severe unintended consequences. The purpose of this review is to put these findings in perspective. The goal is to explain the factors that influence the severity of SWL injury, update current understanding of the long-term consequences of SW damage, describe the physical mechanisms thought to cause SWL injury, and introduce treatment protocols to improve stone breakage and reduce tissue damage.
    Seminars in Nephrology 04/2008; 28(2):200-13. DOI:10.1016/j.semnephrol.2008.01.003 · 3.48 Impact Factor
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