i u rtrt' i ^K't ( V Aar/A7t>ù ~V/T* /,/f/ Jcr(’7urf<>n /u r//// . f7<un</^ lù /i LAtrr. / 6 ---- THE ASSESSMENT OF URINARY STONE FRAGILITY A Thesis submitted by C Dawson BSc, MDBS, FRCS University College Hospital Medical School for the degree of Master of Surgeiy The University of London Department of Urology St Bartholomew’s Hospital London 1996 ProQuest Number: 10017500 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10017500 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 DEDICATION I would like to dedicate this work to my parents, Robin and Shirley, who have supported me in everything I have ever attempted It is through their love and devotion that I have been able to achieve so much. Page 2 SUMMARY AND CONTRIBUTION TO SURGERY Extracorporeal shock wave lithotripsy (ESWL) is the treatment of choice for the majority of patients presenting with symptomatic urinaiy tract calculi. However, at the present time it remains impossible to predict with any degree of certainty those patients in whom ESWL is likely to be successful. Although ESWL remains a success Ail treatment in the majority of patients the expanding use of ESWL to more difficult cases means that in some patients successful stone Augmentation will not occur. The ability to correctly predict in advance those patients in whom ESWL is likely to succeed would allow Urologists to accurately plan treatments and avoid wastage of precious time and resources. The aim of this Thesis was to investigate four techniques to determine whether any of them were able to predict stone Augmentation as measured either by in vitro ESWL Augility, or by microhardness testing on a Shimadzu indenter. The four techniques were; • Porosity estimation • Density estimation • Low-angle X-ray Diffiuction (LAXD) • Magnetic Resonance Imaging (MRI) Page 3 Of these four techniques only density and porosity showed any identifiable trends between stones of different chemical type. The “actual” density (density of the stone material excluding the effect of the pore spaces) was shown for the first time to vary according to the chemical type of stone under consideration. The lithotrip^ e;q)eriment allowed quantification of ESWL fiagility for the first time, with the development of the ESWL score. This will be usefiil for future studies as it also incorporates the Augmentation pattern of the calculus. Both the ESWL fiagility results and the Vickers Hardness number showed clear differences between stones of different chemical type although these two techniques, when compared with each other, showed only a loose correlation. None of the four techniques under investigation showed a significant correlation with Vickers Hardness number. Of the four techniques only porosity and density results were shown to be significantly correlated with ESWL fiagility. In conclusion; the prediction of ESWL fiagility is not yet possible by available techniques. Porosity and density measurements showed some promise, and these should form the basis of future study. Research is also in progress to improve the results of LAXD. The results of this Thesis have contributed towards an understanding of the difficulty of predicting the results of ESWL. Current views on shock wave physics and the way shock waves are thought to cause stone fiagmentation are also discussed. Recent evidence suggests that chemical composition may affect die results of ESWL through the effect that Page 4 the former has on stone porosity and microstructure, and literature is cited to support these views. Further work on the microstructure of calculi is required to determine the effect of stone composition on stone structure and, in turn, the effect this has on stone fragility. Ultimately it is hoped that this research will yield more information about the way in which stone fragmentation occurs, where in the stone it occurs, and how we can develop techniques to predict with certainty when it will occur. Page 5 CONTENTS PAGE Pages Frontispiece Title Page Dedication 2 Summary and Contribution to Surgeiy 3 -5 Contents 6-9 List of Tables 10 List of Figures 11-12 List of Appendices 12 Chapter 1 - Introduction 1.1 Relevance and Importance ofUrinaiy Stone Disease 13-16 1.1.1 Incidence of stone disease, and cost to Health Service 1.1.2 Complications of stone disease 1.2 Current Treatments for Urinaiy Stones 16-19 1.2.1 Choosing the correct Treatment 1.2.2 Conservative Management 1.3 Extracorporeal shock wave lithotripsy 20-39 1.3.1 Comparison of Lithotripters 1.3.2 The Physics of Shock Waves 1.3.3 How Shock Waves fragment Stones 1.3.4 The results of Lithotripsy Page 6 1.3.5 Factors accounting for ESWL failure 1.3.5.1 Factors associated with the patient 1.3.5.2 Factors associated with the Lithotripter 1.3.5.3 Factors associated with the Stone 1.3.6 Complications of Lithotripsy 1.4 The importance of predicting success of Lithotripsy 39 1.5 Methods currently used to predict ESWL success 40-43 1.5.1 Radiological assessment 1.5.2 Ultrasound velocity 1.5.3 Dual Photon Absorptiometry 1.5.4 Scintigraphy 1.6 Current knowledge of Urinaiy Stones 44-60 - the basis for future investigations 1.6.1 The Aetiology ofUrinaiy Stones 1.6.1.1 Crystallisation ofUrinaiy Calculi 1.6.1.2 Promoters of Urolithiasis 1.6.1.3 Inhibitors of Urolithiasis 1.6.2 The Structure and Composition of Stones 1.6.3 The Mechanical Properties of Stones 1.7 Choice of investigative Methods for current study 61-62 Page 7 Chapter 2 - Principles of the Methods used 63 - 73 2.1 Infra red Spectroscopic analysis 2.2 Porosity ofUrinaiy Calculi 2.3 Magnetic Resonance Imaging of Urinary Calculi 2.4 Low Angle X ray diffraction ofUrinaiy Calculi Chapter 3 - Materials and Methods 74 - 95 3.1 Chemical Characterisation 3.2 Measurement of Porosity 3.3 Density Measurement 3.4 Low Angle X ray Diffraction ofUrinaiy CalcuH 3.5 Magnetic Resonance Imaging ofUrinaiy Calculi 3.6 Microhardness testing 3.7 ESWL Fragility Testing Chapter 4 - Results 96 - 140 4.1 Chemical Characterisation 4.2 Porosity 4.3 Density 4.4 LAXD ofUrinaiy Calculi 4.5 MRI ofUrinaiy Calculi 4.6 Microhardness Testing 4.7 ESWL Fragility Testing Page 8 Chapter 5 - Summary of Results 141 -147 Chapter 6 - Discussion 148 - 157 6.1 Infra-red Spectroscopy 6.2 Density and Porosity estimation 6.3 Low Angle X ray Diffraction 6.4 Magnetic Resonance Imaging 6.5 Microhardness Testing 6.6 ESWL fragility Testing 6.7 Conclusions and Future Research Abbreviations Used 158 Presentations / Publications 159-161 References 162-174 Acknowledgements 175-176 Page 9 List of Tables Table 1 Incidence and prevalence rates for Upper tract urinaiy calculi Table 2 Complications ofUrinaiy Stone Disease Table 3 Surgical Options for Stone management Table 4 Conservative Management of Stone Disease Table 5 Reported ESWL success rates for Renal and Ureteric stones Table 6 Distribution of Renal stones and results obtained with ESWL (St Bartholomew’s Hospital data) Table 7 Stones used for LAXD Table 8 Protocol for ESWL Table 9 Chemical composition ofUrinaiy Calculi (1RS) Table 10 Mean density values for each chemical type Table 11 Areas under curves for stones (LAXD experiment) Table 12 Correlation coefficients for LAXD vs other investigations performed Table 13 Correlation coefficients for VHN vs other investigations performed Table 14 Scoring system for ESWL experiment Page 10 LIST OF FIGURES Figure 1 The Advantages and Disadvantages of the three main types of Lithotripter Figure 2 Shock wave generation and coupling, and Localisation modality, for common lithotripters Figure 3 The generation of the shockwave in an electrohydraulic lithotripter Figure 4 The pressure waveform of an electrohydraulic lithotripter Figure 5 Mean Peak positive and negative Pressures delivered by available Lithotripters Figure 6 Results of ESWL, St Bartholomew's Hospital, by size of stone Figure 7 The Crystallisation zones of urine Figure 8 Crystalline Constituents ofUrinaiy Calculi Figure 9 Acoustic and Mechanical Properties of Renal Calculi Figure 10 1RS Spectrum for Calcium Oxalate Figure 11 1RS Spectrum for Struvite Figure 12 1RS Spectrum for Calcium hydrogen phosphate dihydrate (Brushite) Figure 13 1RS Spectrum for Calcium Carbapatite (Apatite) Figure 14 The Nature of Pores in Calculi Figure 15 The Preparation of specimen for Infra red spectroscopy Figure 16 The Experimental set up for the Density Experiment Figure 17 The Experimental set up for LAXD Experiment Figure 18 How the stones were divided using the Exakt saw Figure 19 The Exakt Saw Figure 20 Embedding Technique Figure 21 Polishing the stones manually Figure 22 The automatic Stone polisher Figure 23 The Shimadzu Microhardness Indenter Figure 24 The experimental set up for ESWL Fragility experiment Figure 25 The sieves used for the ESWL Experiment Figure 26 The Porosity ofUrinaiy Calculi (Pilot study) Figure 27 The Porosity ofUrinaiy Calculi (Main experiment) Figure 28 Graph of Mean Density Values (Actual Density) Figure 29 Graph of Mean Density Values (Bulk Density) Figure 30 Regression of Actual Density with