The Respiratory Induced Kidney Motion: Does It Really Effect the Shock Wave Lithotripsy? Mehmet Ozgur Yucel1, Serkan Ozcan2 , Gokhan Tirpan3, Murat Bagcioglu3, Arif Aydin3, Arif Demirbas3, Tolga Karakan3* Purpose: To investigate the effect of respiratory induced kidney mobility on success of shock wave lithotripsy (SWL) with an electrohydraulic lithotripter. Materials and methods: Between May 2013 and April 2015, 158 patients underwent SWL treatment for kidney stones with an electrohydraulic lithotripter. The exclusion criteria were presence of a known metabolic disease (such as cystinuria), non-opaque stones, need for focusing with ultrasonography, abnormal habitus, urinary tract abnormalities, and inability to tolerate SWL until the end of the procedure. Stones greater than 20 mm, and lower pole stones were also excluded. The movement of the kidneys were measured with fluoroscopy guidance. Results: The procedure was successful in 66.7% of the males, and 56.9% of the females. The mean stone size was 11 ± 3 mm in the successful group, and it was 14 ± 4 mm in the unsuccessful group. The mean stone mobility rate was 32 ± 10 in the successful group and 40 ± 11 in the unsuccessful group. Multivariate analysis showed that stone size and kidney mobility affected the success rate significantly, however Hounsfield Unit (HU) did not. Conclusion: The current study shows the significant effect of kidney motion on the success of SWL. Further studies with different lithotripters are needed to determine the significance of kidney mobility. Keywords: kidney motion; kidney stone; shockwave lithotripsy; urolithiasis. INTRODUCTION Shock wave lithotripsy (SWL) was first described in 1980s, and it has become the milestone in the treat- ment of upper urinary tract stone disease(1). Its use in- creased gradually, and currently it has been used even in the treatment of complex stones. A number of factors affect the success rates of SWL. They include stone-related factors including the type and localization of the stone, and its density on com- puterized tomography (CT); and patient-related factors including body habitus, the skin-stone distance (SSD), hydronephrosis and renal functions(2-4). One of the most important problems in SWL is the difficulty to focus on the stone. Focusing is particularly difficult in kid- neys that are hypermobile with respiration. A number of factors including anesthesia, pain, respiratory disorders, and body habitus affect respiration-related mobility of the kidneys. In this study, we aimed to investigate the effect of the kidney motion on success of SWL in a lithotripter with an ellipsoid focus, and a focal zone of 7.5x22 mm. PATIENTS AND METHODS Study design After obtaining approval of the Ankara Training and Research Hospital local ethics committee, 158 patients that had SWL between May 2013 and April 2015 were prospectively included in the study. Preoperative imag- ing included kidney, ureter, and bladder (KUB) X-ray 1Department of Urology, Adiyaman University , Adiyaman, Turkey. 2Department of Urology, Izmir Katip Çelebi University, Izmir, Turkey. 3Department of Urology, Ankara Training and Research Hospital, Ankara, Turkey. *Correspondence: Ankara Hastanesi, Sukriye mah., Ulucanlar Cd., 06340, Ankara, Turkey. Phone/fax : +90 541 5752706/ +90 312 363 3396. E-mail: tolgakarakan@yahoo.com. Received November 2016 & Accepted November 2017 ENDOUROLOGY AND STONE DISEASE and non-contrast enhanced computerized tomography (NCCT). SWL procedure was employed while the patient was in supine position, using Elmed Multimed Classic (Elmed Medical Systems, Ankara, Turkey) electrohydrol- ic device. This device has an ellipsoid focus, the size of its focus is 7.5x22 mm, and its focus length is 135 mm (Table 1). Focusing was done by an experienced urologist, under fluoroscopy and continuous monitor- ing (Flouroscopy targeting and monitoring every 250 pulses). The procedure was done under intramuscular analgesia (Diclofenac sodium). The patients were ad- ministered 2000 shocks in every session, at 14-18 kv with stepwise voltage ramping, and 60 pulses/min. The patients' body was fixed to the tables with markers to avoid body movement during sessions. The patients were examined with KUB and ultrasonog- raphy to determine stone disintegration, and the degree of hydronephrosis one week after every session. SWL was done up to 3 sessions if there was no progression in hydronephrosis, and the patient was willing to keep up with SWL. None of the patients had more than 3 SWL sessions. The procedure ended when stone disin- tegration was achieved, ant the patient was stone free on follow up. Both KUB and ultrasonography were obtained on fol- lows up visits of the patients performed 1 and 3 months after the last successful SWL session, and NCCT was obtained when needed. The patients with insignificant residual stone fragments (< 3 mm residual fragments) Vol 15 No 01 January-February 2017 11 were regarded as stone free. Study population Patients with stone size less than 20 mm were includ- ed in the study. The exclusion criteria were presence of a known metabolic disease (such as cystinuria), non- opaque stones, need for focusing with ultrasonography, abnormal habitus, urinary tract abnormalities, previous renal surgery and inability to tolerate SWL until the end of the procedure. The stones greater than 20 mm and lower pole stones were also excluded. Lower pole stones excluded due to its high SWL failure. Measurements The size of the stone was calculated taking the longest axis of the stone on KUB into consideration. The ratio of the size of the stone measured on KUB and the size of the stone measured on fluoroscopy was calculated. The center of the stone and the center of the fluorosco- py were marked when the patient was monitored with fluoroscopy. Then, cranial and caudal motion of the stone was marked on fluoroscopy, and the motion of the kidney on fluoroscopy was calculated by compar- ing it with the stone size (Figure 1). The size of the stone was not measured between the sessions. Only the motion values measured at the first measurement were taken into consideration in the study. The movements of the kidney were measured three times at the beginning, middle and end of the procedure. In the next SWL ses- sions measurement was not done considering the disin- tegration of the stones. Statistical analysis Statistical analysis of data was performed with SPSS IBM PASW 18. Descriptive statistics were given as mean, standard deviation, frequency, and percent. The normality of distribution was tested with Shapiro Wilks Test for continuous variables. Student T test was used if the distribution was normal, and Mann Whitney U Test was employed if the distribution was not normal. Cat- egorical variables were analyzed with Fisher’s Exact Test. Univariate and multivariate regression analysis models were used to analyze the effects of different fac- tors on the success rate of SWL. The results that were significant (p value < 0.05 statistically significant) and near significant variables on univariate analysis were analyzed with multivariate logistic regression test. RESULTS The patient characteristics and demographic data are presented in Table 2. The success rate of SWL was analyzed statistically in relation with the mean age, sex, side of the kidney with stone, localization of the stone, (Hounsfield Unit) HU of stone, and kidney motion. The mean age was 39 ± 11 years in the patients with a suc- cessful result, and 46 ± 13 years in the ones with an unsuccessful result. The procedure was successful in 66.7% of the males, and 56.9% of the females. Presence of the stone in the right or the left kidneys, in the upper or renal pelvis were not found as significant factors for the success of treatment. The successful and unsuccess- ful groups were similar for age and gender as well as the side and localization of the stone. Univariate analysis showed that size of the stone, HU of the stone, and kidney motion affected the success of SWL significantly. Multivariate analysis showed that stone size and kidney motion affected the success rate significantly, however HU did not. DISCUSSION Advances in endourological procedures such as retro- grade intrarenal surgery (RIRS) and percutaneous neph- rolithotomy (PNL), and high success rates obtained with those procedures make one ask whether SWL los- es its value as a gold standard treatment modality(5-7). Therefore, it is important to know the success rate of SWL in different patient groups. Stone parameters, pa- tient characteristics, and types of lithotripters have been investigated for their effects on the success of SWL(8-10). Some of the most important factors that affect the suc- cess of SWL are correct focusing on the stone, and mon- itoring the stone with fluoroscopy. The kidney motion Table 1. Descriptive analysis of patients and treatment parameters Age* (year) 42 ± 1.5 (22-73) Mean stone HU* 662 ± 14.7 (369-1453) Stone size* (mm) 12.2 ± 0.2 (6-20) Mean kidney mobility* (mm) 35 ± 0.8 (10-67) Success Rate % (N) %62.7 (99) Size of focal area (mm) 7.5x22 Mean shockwaves number 1752 ± 321 ( 412-2000) Mean energy (kV) * 15.01 ± 0.3(12-18) Shock wave rate (per minute) 60 Mean shockwave session 2.68 Abbreviations: HU, Hounsfield unit * Mean ± SD (Range) Univariate Analysis Multivariate Analysis Success Failure p value OR 95%CI p value Age* (year) 39 ± 11 46 ± 13 0.057 1.03 0.98-1.09 0.234 Gender (%) 0.463 - - - Female, N(%) 37 (56,92%) 28 (43,08%) - - - Male, N(%) 62 (66,66%) 31(33,34%) - - - Side (%) 0.711 - - - Right, N(%) 49 (49,5%) 31 (52,5%) - - - Left, N(%) 50 (50,5%) 28 (47,5%) - - - Stone size* (mm) 11 ± 3 (6-20) 14 ± 4 (8-20) < 0.001 1.62 1.19-2.21 0.002 Mean stone HU* 771 ± 194 (369-1453) 829 ± 141(418-981) 0.012 1.01 0.99-1.01 0.534 Mean kidney mobility* (mm) 32 ±10 (10-67) 40 ±11(15-60) < 0.001 1.12 1.04-1.21 0.003 Stone location (%) 0.064 0.24 0.05-1.16 0.077 Upper/mid calyceal, N(%) 42 (42,4%) 34 (57,7%) Renal pelvis/UPJ, N(%) 57 (57,6%) 25 (42,3%) Table 2. Patients demographics and analysis of SWL success rate. Abbreviations: SWL, shock wave lithotripsy; HU, Hounsfield unit; * Mean ± SD (Range) Respiration induced kidney mobility in SWL-Yucel et al. Endourology and Stone Diseases 12 due to respiration usually makes difficult to keep the stone in the focal zone of the lithotripter. Kidney mo- tion due to respiration may be up to 5-50 mm, and this shows that more than 50% of the shock waves remain out of the focal zone of the lithotripter(11-15). An in vitro study made with a lithotripter with a focal zone of 4.5 mm showed that fragmentation effect decreased signif- icantly when motion was more than 10 mm(16). A recent magnetic resonance imaging (MRI) study showed that the motion was 8.9 mm for the right, and 8.48 mm for the left kidneys in awake individuals, and those values were greater in the individuals under general anesthesia .(14) Correct focusing of the SWL shock waves on the stone is important both for SWL success and prevention of parenchymal injury(17). In these studies, kidney mo- bility was measured by ultrasound, MRI and CT which is dissimilar to our study. Although the measurement used in our study is an analytical measurement, the greatest advantage is that the measurements are made during the process. Various systems have been developed for continuous localization before shock wave firing, such as ultra- sonography and tracking algorithms to solve respira- tion-related focusing problems(17,18). Performing SWL under general anesthesia, and con- trolling and coordinating the respiratory movements of the patient with the SWL sequences are the main meas- ure to prevent respiratory movements which impair suc- cess of SWL. A number of studies showed better results with general anesthesia compared to sedation(19-22). The success rates under sedoanalgesia were reported as 52- 72% in those studies. Other parameters that affect the success of SWL are SSD, type of the stone, and stone HU. Various stud- ies showed the effects of SSD on the success of SWL on kidney stones. Studies reported that the success of SWL decreased when SSD was >10 cm(23,24). Another mechanism that affects the success of SWL is the fo- cal zone of the device. In vitro studies showed that the lithotripters with broader focal zones had higher capac- ities to break the stones(25,26). However, it must be kept in mind that injury to neighboring tissues increases as the focal zone gets broader. Two different zones may be used in MODULITH SLX-F2 urologic workstation (Storz-Medical, Kreuzlingen, Switzerland). The broad- er focal zone (50x9 mm) is used in kidney stones, and the narrow focal zone (28x6 mm) is used in the ure- teral stones. However, the clinical results did not show any improvement in the effectivity(26). In a very recent study, Harrogate et al. investigated kidney motion, and found stone motion secondary to respiration as 7.7±2.9 mm for kidney stones, and 3.6 ± 2.1 mm for ureteric stones in patients who were not under anesthesia(27). Dif- ferent from other studies, in that study it was suggested that respiration-related motion was less in conscious patients without any anesthesia. Another study that in- vestigated SWL success in relation with respiration-as- sociated movement in 10 patients reported mean motion as 1.5 ± 0.3 cm with ultrasonography, and it was seen that approximately 40% of the shock waves missed the stone(28). We found a greater mean motion in this study. This difference may be related to different measure- ment methods of movements among studies, including ultrasonography, MRI and CT instead of fluoroscopy in other studies. In addition, in our study we calculated the sum of cranial and caudal movements. A number of hypotheses have been proposed for stone disintegration. Broader focal zone, slower pulse rate, adequate coupling of shock wave head, and active mon- itoring increase success of SWL(25). The main limitations of our study are use of a single lithotripter, and absence of SSD data and stone analy- sis. Another limitation is making measurements under fluoroscopy without any electronic measurement, chas- ing the movements visually, and manual measurement of the points and distances with maximum movement. However, there are only scarce reports in the literature that have investigated respiration-related motion on the success of SWL. To our knowledge, this is one of the first studies that included the highest number of pa- tients, and analyzed a number of parameters in relation with motion. CONCLUSIONS In our study, we observed a statistically significant re- lationship between kidney motion and success of SWL. Further comparative studies using lithotripters with dif- ferent focal zones are needed to determine the signif- icance of kidney motion on different focal zones and different devices. CONFLICT OF INTEREST The authors report no conflict on interest. Figure 1. The method used to measure the actual mobility (M). A: Craniocaudal size of the stone on kidney-ureter-bladder X-ray, B: The size of the stone under fluoroscopy, C: The mobility of the stone with respiration. M=AxC/B (Calculation of actual mobility by calculat- ing the ratio of the actual size of the stone on kidney-ureter-bladder X-ray and its size on fluoroscopy). Respiration induced kidney mobility in SWL-Yucel et al. Vol 15 No 01 January-February 2017 13 REFERENCES 1. Chaussy C, Brendel W, Schmiedt E. Extracorporeally induced destruction of kidney stones by shock waves. Lancet 1980;13;2:1265-8. 2. Wiesenthal JD, Ghiculete D, Ray AA, Honey RJ, Pace KT. A clinical nomogram to predict the successful shock wave lithotripsy of renal and ureteral calculi. J Urol. 2011; 186:556-62. 3. Gupta NP, Ansari MS, Kesarvani P, Kapoor A, Mukhopadhyay S. Role of computed tomography with no contrast medium enhancement in predicting the outcome of extracorporeal shock wave lithotripsy for urinary calculi. BJU Int. 2005; 95:1285-8. 4. Semins MJ, Matlaga BR. Strategies to optimize shock wave lithotripsy outcome: Patient selection and treatment parameters. World J Nephrol. 2015; 6;4:230-4. 5. Donaldson JF, Lardas M, Scrimgeour D, Stewart F, MacLennan S, Lam TB. Systematic review and meta-analysis of the clinical effectiveness of shock wave lithotripsy, retrograde intrarenal surgery, and percutaneous nephrolithotomy for lower-pole renal stones. Eur Urol. 2015; 67:612-6 6. Resorlu B, Unsal A, Ziypak T, Diri A, Atis G, Guven S. Comparison of retrograde intrarenal surgery, shockwave lithotripsy, and percutaneous nephrolithotomy for treatment of medium-sized radiolucent renal stones. World J Urol. 2013; 31:1581-6 7. Telli O, Haciyev P, Karimov S, Sarici H, Karakan T, Ozgur BC, Demirbas A, Resorlu B, Soygur T, Burgu B. Does previous stone treatment in children generate a disadvantage or just the opposite? Urolithiasis 2015; 43:141- 5. 8. Wiesenthal JD, Ghiculete D, Ray AA, Honey RJ, Pace KT. A clinical nomogram to predict the successful shock wave lithotripsy of renal and ureteral calculi. J Urol. 2011; 186:556-62. 9. Ordon M, Ghiculete D, Pace KT, Honey RJ. Does the radiologic technologist or the fluoroscopy time affect treatment success with shockwave lithotripsy? J Endourol. 2012; 186:556-62. 10. Bhojani N, Lingeman JE. Shockwave lithotripsy-new concepts and optimizing treatment parameters. Urol Clin North Am. 2013; 40:59-66. 11. Davies SC, Hill AL, Holmes RB, Halliwell M, Jackson PC. Ultrasound quantitation of respiratory organ motion in the upper abdomen. Br J Radiol. 1994;67:1096-102. 12. Balter JM, Ten Haken RK, Lawrence TS, Lam KL, Robertson JM. Uncertainties in CT- based radiation therapy treatment planning associated with patient breathing. Int J Radiat Oncol Biol Phys. 1996; 1;36:167-74. 13. Schwartz LH, Richaud J, Buffat L, Touboul E, Schlienger M. Kidney mobility during respiration. Radiother Oncol. 1994; 32:84-6 14. Song R, Tipirneni A, Johnson P, Loeffler RB, Hillenbrand CM. Evaluation of respiratory liver and kidney movements for MRI navigator gating. J Magn Reson Imaging 2011; 33:143- 8. 15. Sorensen MD, Bailey MR, Shah AR, Hsi RS, Paun M, Harper JD. Quantitative assessment of shockwave lithotripsy accuracy and the effect of respiratory motion. J Endourol. 2012; 26:1070-4. 16. Cleveland RO, Anglade R, Babayan RK. Effect of stone motion on in vitro comminution efficiency of Storz Modulith SLX. J Endourol. 2004; 18:629-33 17. Orkisz M, Farchtchian T, Saighi D, Bourlion M, Thiounn N, Gimenez G. Image based renal stone tracking to improve efficacy in extracorporeal lithotripsy. J Urol. 1998; 160:1237-40. 18. Bohris C, Bayer T, Lechner C. Hit/Miss monitoring of ESWL by spectral Doppler ultrasound. Ultrasound Med Biol. 2003; 29:705-12. 19. Sorensen C, Chandhoke P, Moore M, Wolf C, Sarram A. Comparison of intravenous sedation versus general anesthesia on the efficacy of the Doli 50 lithotriptor. J Urol. 2002;168:35-7. 20. Eichel L, Batzold P, Erturk E. Operator experience and adequate anesthesia improve treatment outcome with third generation lithotripters. J Endourol. 2001;15:671-3. 21. Hosking DH, Smith WE, McColm SE. A comparison of extracorporeal shock wave lithotripsy and ureteroscopy under intravenous sedation for the management of distal ureteric calculi. Can J Urol. 2003;10:1780-4. 22. Pareek G, Hedican SP, Lee FT Jr, Nakada SY. Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005; 66:941-4 23. Patel T, Kozakowski K, Hruby G, Gupta M. Skin to stone distance is an independent predictor of stone-free status following shockwave lithotripsy. J Endourol. 2009; 23:1383-5. 24. Pareek G, Hedican SP, Lee FT Jr, Nakada SY. Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005; 66:941-4. 25. Rassweiler JJ, Knoll T, Köhrmann K-U, et al. Shock Wave Technology and Application: An Update. European Urology 2011; 59:784-96. 26. De Sio M, Autorino R, Quarto G, Mordente S, Giugliano F, Di Giacomo F, et al. A new transportable shock-wave lithotripsy machine for managing urinary stones: a single-centre experience with a dual-focus lithotripter. BJU Int. 2007 ;100:1137-41. 27. Harrogate S, Yick S, Williams JC, Cleveland Respiration induced kidney mobility in SWL-Yucel et al. Endourology and Stone Diseases 14 R, Turney BW. Quantification of the range of motion of kidney and ureteric stones during shockwave lithotripsy in conscious patients. J Endourol. 2016;30:406-10. 28. Sorensen MD, Bailey MR, Shah AR, Hsi RS, Paun M, Harper JD. Quantitative assessment of shockwave lithotripsy accuracy and the effect of respiratory motion. J Endourol. 2012;26:1070-4. Respiration induced kidney mobility in SWL-Yucel et al. Vol 15 No 01 January-February 2017 15