- Email: [email protected]
Comparison of a Reduced Radiation Fluoroscopy Protocol to Conventional Fluoroscopy During Uncomplicated Ureteroscopy
Endourology and Stones Comparison of a Reduced Radiation Fluoroscopy Protocol to Conventional Fluoroscopy During Uncomplicated Ureteroscopy Daniel J. Greene, Christopher F. Tenggadjaja, Ryan J. Bowman, Gautum Agarwal, Kamyar Y. Ebrahimi, and D. Duane Baldwin OBJECTIVES
METHODS
RESULTS
CONCLUSIONS
Although the long-term effects of radiation exposure are not completely predictable, the principle of keeping radiation exposure “as low as reasonably achievable” should be used. The purpose of this study was to compare fluoroscopy times before and after the implementation of a protocol designed to reduce fluoroscopy usage during ureteroscopy. A retrospective review was conducted of 300 consecutive ureteroscopy patients at a single institution. Patients undergoing simple ureteroscopy without ancillary procedures or balloon dilation were further evaluated to determine the effect of a reduced fluoroscopy protocol. The protocol included several measures, including use of a laser-guided C-arm, use of a designated fluoroscopy technician and substitution of visual for fluoroscopic cues during ureteroscopy. Fluoroscopy times were compared between groups using a paired t test with P ⬍ .05 considered significant. Ureteroscopy cases before protocol implementation (n ⫽ 30) were compared with procedures after implementation (n ⫽ 30). Stone size and location were similar between groups. Protocol implementation significantly reduced the mean fluoroscopy exposure from 86.1 seconds (range 30-300) to 15.5 seconds (range 0-54; P ⬍ .001). There was no difference in mean operative time (74.2 vs 65.1 minutes; P ⫽ .14), or complications (2 patients vs 2 patients; P ⫽ 1) between groups. No complication in either group could be ascribed to the fluoroscopic technique. The reduced fluoroscopy protocol resulted in an 82% reduction in fluoroscopy time without altering patient outcomes. These simple radiation-reducing techniques add no technical difficulty and improve safety for the patient, surgeon, and operating room staff by lowering radiation exposure. UROLOGY 78: 286 –290, 2011. © 2011 Elsevier Inc.
F
luoroscopic imaging plays a crucial role during many routine minimally invasive procedures, including ureteroscopic lithotripsy.1 The increasing use of fluoroscopy has prompted the Food and Drug Administration to release a public health advisory educating physicians and patients of the need to limit radiation exposure to reduce potential negative effects of excessive radiation exposure.2 There is no known safe lower limit of radiation exposure below which the patient will experience no harmful effects. All ionizing radiation carries with it the potential to cause cancer.3 Thus, an increased use of radiation carries with it the potential to increase a patient or population’s risk for developing From the Department of Urology, Loma Linda University Medical Center, Loma Linda, California Reprint requests: D. Duane Baldwin, Department of Urology, Loma Linda University School of Medicine, 11234 Anderson Street, Room A560, Loma Linda, CA, 92354. E-mail: [email protected] Submitted: June 4, 2010; accepted (with revisions): November 14, 2010
286
© 2011 Elsevier Inc. All Rights Reserved
cancer.4 Whenever patients are exposed to radiation, a fundamental principle of radiation usage should be to decrease the exposure to the lowest dosage possible “as low as reasonably achievable” (ALARA).5 One of the major areas where urologists can control the administration of radiation is during fluoroscopic imaging. Fluoroscopy is used to diagnose and document the location of stones and filling defects during endoscopic cases, to ensure the safe passage of instruments and tools into the urinary tract, and to assist in renal mapping during endoscopy. Although the amount of radiation received from fluoroscopy during simple ureteroscopy may not be large compared with the dosages received from diagnostic modalities like computed tomography (CT) scanning or therapeutic purposes like cancer treatment, the effects of radiation are cumulative.6 In addition, the high-volume urologist who performs hundreds of endoscopic cases per year may be exposed to increased amounts of scattered radiation during these procedures. 0090-4295/11/$36.00 doi:10.1016/j.urology.2010.11.020
Table 1. Radiation-reducing measures Before Protocol Estimation of location of kidney and bladder visually Fluoroscopic guidance to confirm placement of guidewire and stent Review of imaging, without measurement of stone location with respect to bony landmarks Fluoroscopic confirmation of stone location Fluoroscopy without regard for respiratory motion Randomly assigned fluoroscopy technicians Fluoroscopic confirmation of stent bladder curl Retrograde pyelogram to look for filling defects in ureter Continuous fluoroscopy mode for portions of wire, stent, and scope positioning
Fluoroscopy-Reducing Protocol Use of laser guided C-arm Visual and tactile cues for guidewire and stent placement Detailed review of prior imaging, including identification of level of stone and distance from iliac crest and lumbar vertebrae Imaging present on high-definition screen in front of surgeon during case Activation timed with respiration Usage of designated fluoroscopy technician Visual confirmation of stent bladder curl with cystoscopy Visual confirmation of stone location with ureteroscopy Single pulse fluoroscopy mode for portions of wire, stent, and scope positioning
There are several potential techniques that could be used to decrease both patient and staff radiation exposure during ureteroscopic lithotripsy. Well-established techniques include the use of lead shielding, increasing the distance from the exposure source, and decreasing the kVp or mAs for the source. One of the simplest and most effective techniques to reduce radiation exposure is to decrease fluoroscopy time during endoscopic procedures, including ureteroscopy.5,7 In an attempt to minimize radiation exposure for patients and staff during ureteroscopy, a reduced fluoroscopy protocol was instituted in our center. The purpose of this study was to compare the fluoroscopy times and patient outcomes in ureteroscopy patients before and after the implementation of this reduced fluoroscopy protocol.
MATERIAL AND METHODS Institutional review board approval at Loma Linda University Medical Center was obtained for a retrospective analysis of 300 consecutive patients in a single institution who underwent endoscopic stone surgery between November 2006 and September 2009 by a single endoscopic surgeon. All patients underwent ureteroscopy and laser lithotripsy, with only the fluoroscopy technique varying between groups. Patients requiring ureteral balloon dilation, undergoing ancillary procedures, or with entombed stents or bladder stones were excluded from analysis. Patient demographics, stone size and location, body mass index (BMI), complications, operating time, and fluoroscopy time were obtained and compared between groups. Stone area was measured in the 2 largest dimensions. In January 2009, specific radiation-reducing measures were instituted in an attempt to decrease the fluoroscopy exposure for patients undergoing ureteroscopy (Table 1). Before implementing these measures, standard practice was to use fluoroscopy to identify the stone, place guidewires and the ureteroscope, and view the curl of the stent in the bladder and renal pelvis. Imaging was present on the computer, but not in direct view of the scrubbed surgeon. The new radiation-reducing measures started with a detailed review of prior imaging immediately before the start of a case to prevent excess imaging of nonessential areas. The imaging was present in front of the scrubbed UROLOGY 78 (2), 2011
surgeon on a high-definition monitor for the entire case. The stone location was identified with respect to the bony landmarks, including lumbar vertebrae and iliac crest. Films were then available throughout the case for referral if there were any doubts as to anatomy or stone location. A GE OEC 9900 Elite (General Electric Healthcare, Waukesha, WI) portable C-arm fluoroscopy machine was used, which was equipped with a laser pointer to aid in positioning the machine before activation of the beam (Fig. 1(A)). This allowed the correct positioning of the C-arm before activation and prevented the need to acquire additional images to center the beam on the area of interest. The C-arm activation was also timed with the patient’s respiration (end expiration) to minimize kidney movement and image distortion because this is the longest and most reproducible phase of the respiratory cycle.8 Visual cues were then sought on the static image preserved upon the monitor rather than viewing real-time fluoroscopic images. In each case, a designated fluoroscopy technician was used who was acquainted with the protocol goals and completely familiarized with the fluoroscopy machine usage and relevant urological anatomy. During passage of the guidewires, dual lumen catheter and/or ureteroscope, the surgeon made use of tactile cues and external visual cues as opposed to relying upon only fluoroscopic cues. Thus, fluoroscopic imaging was required only when an obstruction was felt or to confirm final placement in the kidney. Instead of acquiring fluoroscopic confirmation during placement of a second wire, the surgeon relied on tactile cues and inspection of the length of the wire compared with the wire currently in place (Fig. 1(B)). At the conclusion of the procedure, the stent was placed under direct cystoscopic visualization for the bladder coil, and a short fluoroscopy activation for placement of the renal coil. Renal mapping was performed by taking a single film of the contrast-filled renal collecting system to provide a road map. Calyces were then visually inspected, ensuring that the correct number and location of calyces had been endoscopically visualized rather than relying on real-time fluoroscopy. Fluoroscopic times, operative times, stone cross-sectional area, age, and BMI were compared before and after protocol implementation using a paired t-test. Categorical variables, such as gender, complications, stone-free rates, and repeat procedures were compared before and after protocol implementation using a Fisher’s exact test. In addition, a multivariate 287
Figure 1. (A). Laser-guided C-arm. (B) Comparing the length of the 2 wires for placement confirmation without the use of additional fluoroscopy. Table 2. Preoperative characteristics Before Protocol (n ⫽ 30) Mean age in years (range) Mean stone area in mm2 (range) Stone composition (%) Analysis not done Calcium oxalate Calcium phosphate Uric acid Cystine Other Gender M/F (%M/%F) Mean BMI in kg/m2 (range)
After Protocol (n ⫽ 30)
P Value
49.8 (27-69) 106.4 (12-500)
55.6 (26-88) 100.1 (12-349.1)
.11 .81
13 (43.3) 8 (26.7) 7 (23.3) 1 (3.3) 1 (3.3) 0 (0) 17/13 (56.7/43.3) 29.7 (19.8-45.5)
10 (33.3) 13 (43.3) 6 (20.0) 0 (0) 0 (0) 1 (3.3) 13/17 (43.3/56.7) 26.4 (18-41)
.31 .03
Table 3. Outcome characteristics
Mean fluoroscopy time in seconds (range) Mean operative time in minutes (range) No. complications (%) No. Stone-free patients (%) No. needed repeat procedure (%)
Before Protocol (n ⫽ 30)
After Protocol (n ⫽ 30)
P Value
86.1 (21.6-300) 74.2 (30-187) 2 (6.67) 25 (83.3) 2 (6.67)
15.5 (0-54) 65.1 (27-155) 2 (6.67) 25 (83.3) 2 (6.67)
⬍.01 .14 1.00 1.00 1.00
regression analysis was used to control for confounding factors. Statistics were run in SPSS version 16 (SPSS, Inc., Chicago, IL) and a P value ⬍ 0.05 was considered significant.
RESULTS The mean age of all patients was 52.7 years (range 26-88 years) and mean BMI was 28.1 kg/m2 (range 18-45.5 kg/m2). Sixty ureteroscopic surgeries were identified that did not include stones in multiple locations, bladder stones, entombed stents, steinstrasse, or ureteral balloon dilation. Thirty ureteroscopic cases were analyzed before protocol implementation, and 30 cases were compared 288
after protocol implementation (Table 2). The mean fluoroscopy time was 86.1 seconds before implementation and 15.5 seconds (P ⬍ .001) after protocol implementation (Table 3). A multivariable regression analyzed fluoroscopy time against age, BMI, operative time, and stone cross-sectional area. No significant confounders were observed between fluoroscopy time and these dependent variables. In addition, age (P ⫽ .56), operative time (P ⫽ .14), stone area (P ⫽ .96), and complications (P ⫽ 1.00) were similar between the 2 groups. The BMI was greater for the group before protocol 29.7 vs 26.4 (P ⫽ .03) but did UROLOGY 78 (2), 2011
not affect fluoroscopy time when analyzed in the multivariate regression analysis (P ⫽ .62). There were 2 complications in the first group and 2 in the second (P ⫽ 1.00). In both the standard fluoroscopy protocol and the reduced fluoroscopy protocol, the complications included 1 case of sepsis and urinary tract infection in each group. No complications appeared to be related to fluoroscopic imaging technique. Similar stonefree rates were seen in each group (83% vs 83% and P ⫽ 1.00). The number of retreatments required in each group was also the same, with 2 (7%) in each group (P ⫽ 1.00). There was no significant difference in stone chemical composition between the groups (Table 2).
COMMENT In urology, fluoroscopic imaging plays a major role in endoscopic surgery. Current American Urological Association guidelines recommend ureteroscopy as a first-line treatment for symptomatic ureteral calculi.9 Further increasing the use of ureteroscopy, data from the National Health and Nutrition Examination Survey indicate that a lifetime prevalence of kidney stones in the United States is greater than 5% and this number is increasing.10 The cause of this increase in stone prevalence is unknown but possibly linked to an increased rate of obesity, decreased calcium intake, or better stone detection.10,11 This translates into an 83% increase in the number of ureteroscopies performed in the United States from 1994 to 2004.12 Fluoroscopic imaging is used extensively during ureteroscopy to direct placement of guidewires, locate stones, monitor ureteral dilation, perform renal mapping, and place ureteral stents. As application of ureteroscopic techniques increases, the radiation exposure of patients and staff members will also increase. This study demonstrates that the measures instituted in the reduced fluoroscopy protocol were effective in reducing the fluoroscopy time and thereby the radiation dose to the patient, surgeon, and staff. Before protocol implementation, the mean fluoroscopy time was 89.5 seconds. This value is similar to the 78-second fluoroscopy time previously reported during uncomplicated ureteroscopy by Hellawell and colleagues.13 After protocol implementation, however, the time was reduced to 15.5 seconds. This represents an 82% reduction in fluoroscopy time and consequently a proportional reduction in radiation exposure. This radiation reduction was accomplished with minimal additional effort or technical procedural modification. The reduced fluoroscopy protocol did not increase the subjective complexity of the case. Importantly, our study demonstrates that the reduced radiation protocol did not increase surgical complexity, operative time, residual stone rates, or complication rates. The risks of ionizing radiation can be divided into 2 categories: deterministic and stochastic.3 Deterministic effects are those for which a threshold exists above which damage will be apparent, and as the dose increases, so UROLOGY 78 (2), 2011
does the severity of the injury. Several of these types of injuries are documented in various fields, especially cardiology.14,15 Some of these injuries include skin erythema, ulcers, telangiectasia, and dermal atrophy.14 Yet it appears that fluoroscopic imaging during ureteroscopy for stone treatment results in radiation levels below those required for deterministic effects.7,13 In contrast, theoretically the stochastic effects lack a threshold of injury. Cancer is an example of a stochastic injury that may be induced at any radiation dose, but the probability increases with increased dose.3 In fact, it is estimated that 5695 (0.9%) cases of cancer in the United States each year occur because of medically-imposed ionizing radiation.4 To decrease this theoretical risk of cancer and other stochastic effects, the principle of ALARA should be observed and the lowest possible radiation dosage used that will allow the safe completion of the procedure. Although fluoroscopy for ureteroscopy uses a relatively low dose of radiation, the cumulative effects can pose a theoretical risk of cancer. Hellawell determined that surgeons received a mean of 11.6 Gy per urological case.13 Although this individual dose is low, when one considers that high-volume surgeons may perform up to 500 cases per year, this would result in 5.8 mGy per year. This is more than half of the effective dose of a noncontrast CT scan of the abdomen. When factored over a surgeon’s 30-year career, this would be equal to 174 mGy, equal to the effective radiation dose of more than 17 noncontrast abdominal CT scans or 8700 chest x-rays.16 Ionizing radiation has the potential to cause leukemia, lymphomas, and various other solid cancers.6 Certainly, any effort that would reduce radiation exposure for the staff and patient without compromising patient outcomes would be desirable. In an effort to understand and reduce radiation exposure to patients, several fields of medicine have examined their use of fluoroscopy.17,18 An orthopedic study attempted a fluoroscopy-reducing protocol that included a laser-guided C-arm and found a 32% reduction in fluoroscopic time.19 To the best of our knowledge, our study appears to be the first to use these specific modifications to a reduced radiation protocol for ureteroscopic laser lithotripsy. One possible limitation of this study is that it is retrospective and patients were not randomized. Based on the initial success with this reduced fluoroscopy protocol, it was felt that a prospective study would not be ethical. Another limitation of this study is that specific radiation exposures were not determined, but rather relative amounts were compared using fluoroscopy time. In each patient, the mAs and kVp setting were not recorded. Some have argued that fluoroscopy time is not a good marker of radiation exposure.20,21 Certainly, the radiation dose is affected by patient size and hence skin dosages will be higher in obese compared with thin patients. Yet, fluoroscopy time is a major determinant of a patient’s individual radiation dose.7 Thus, if one were 289
to reduce an individual’s fluoroscopy time, the radiation dose would concurrently be reduced. At present, we are also developing reduced mA and kVp protocols to further limit radiation dose in patients. Another possible limitation of the study was the difference in BMI between groups. This difference did not affect fluoroscopy time, as was demonstrated in the multivariate analysis. The preliminary results in this study suggest that major reductions could be made in radiation exposure during fluoroscopy without compromising patient outcome. Certainly, these results will need to be confirmed in other centers. Fluoroscopic imaging during ureteroscopy is an integral part of endoscopic surgery, which allows safe and effective treatment. It is vital that, as reduced fluoroscopy protocols are developed, measures are taken to ensure that patient outcomes are not compromised. It is possible that with future developments in endourology, other techniques will further reduce or even completely remove radiation exposure during endoscopic cases. Until that time, urological surgeons should adhere to the principles of ALARA in an attempt to reduce the radiation dose for the safety of their patients, staff, and themselves.
CONCLUSIONS This reduced fluoroscopy protocol resulted in an 82% reduction in fluoroscopy time without altering patient outcomes. These simple radiation-reducing techniques add no technical difficulty to the case and may improve procedure safety for the patient, surgeon, and operating room staff. References 1. Miller DL. Overview of contemporary interventional fluoroscopy procedures. Health Phys. 2008;95:638. 2. US Food and Drug Administration. Public Health Advisory: Avoidance of serious X-Ray Induced Skin Injuries to patients during Fluoroscopically Guided procedures. 1994. 3. Mahesh M. Fluoroscopy: patient radiation exposure issues. RadioGraphics. 2001;21:1033. 4. Berrington de Gonzalez A, Darby S. Risk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries. Lancet. 2004; 363:345.
290
5. Mantu-Gupta MMCO, Jay MD, Shah B, et al. Percutaneous management of the Upper Urinary Tract. In: Alan M, Wein J. Wien: Campbell-Walsh Urology, 9th ed. Philadelphia: Saunders Elsevier, 2007. 6. Yoshinaga S, Mabuchi K, Sigurdson AJ, et al. Cancer risks among radiologists and radiologic technologists: review of epidemiologic studies. Radiology. 2004;233:313. 7. Bagley DH, Cubler-Goodman A. Radiation exposure during ureteroscopy. J Urol. 1990;144:1356. 8. Chang JY, Balter P, Komaki R. Image-guided stereotactic body radiation therapy for early-stage non-small cell lung cancer. In: Cox JD, Chang JY, Komaki R. Image-Guided Radiotherapy of Lung Cancer. New York: Informa HealthCare, 2007. 9. Preminger GM, Tiselius HG, Assimos DG, et al. Guideline for the management of ureteral calculi. J Urol. 2007;178:2418. 10. Stamatelou KK, Francis ME, Jones CA, et al. Time trends in reported prevalence of kidney stones in the United States: 19761994. Kidney Int. 2003;63:1817. 11. Goldfarb DS. Increasing prevalence of kidney stones in the United States. Kidney Int. 2003;63:1951. 12. Bratslavsky G, Moran ME. Current trends in ureteroscopy. Urol Clin North Am. 2004;31:181. 13. Hellawell GO, Mutch SJ, Thevendran G, et al. Radiation exposure and the urologist: what are the risks? J Urol. 2005;174:948. 14. Koenig TR, Wolff D, Mettler FA, et al. Skin injuries from fluoroscopically guided procedures: part 1, Characteristics of radiation injury. AJR Am J Roentgenol. 2001;177:3. 15. Shope TB. Radiation-induced skin injuries from fluoroscopy. RadioGraphics. 1996;16:1195. 16. Shrimpton PC Hillier MC, Lewis MA, et al. Doses From Computed Tomography (CT) Examinations in the UK: 2003 Review. NRPBW67. Chilton: NRPB; 2005. 17. Papaioannou S, Afnan M, Coomarasamy A, et al. Long term safety of fluoroscopically guided selective salpingography and tubal catheterization. Hum Reprod. 2002;17:370. 18. Perisinakis K, Theocharopoulos N, Damilakis J, et al. Estimation of patient dose and associated radiogenic risks from fluoroscopically guided pedicle screw insertion. Spine. 2004;29:1555. 19. Proschek D, Kafchitsas K, Rauschmann MA, et al. Reduction of radiation dose during facet joint injection using the new image guidance system SabreSource: a prospective study in 60 patients. Eur Spine J. 2009;18:546. 20. Balter S. Capturing patient doses from fluoroscopically based diagnostic and interventional systems. Health Phys. 2008;95:535. 21. Taylor JB, Selzman KA. An evaluation of fluoroscopic times and peak skin doses during radio frequency catheter ablation and biventricular internal cardioverter defibrillator implant procedures. Health Phys. 2009;96:138.
UROLOGY 78 (2), 2011
METHODS
RESULTS
CONCLUSIONS
Although the long-term effects of radiation exposure are not completely predictable, the principle of keeping radiation exposure “as low as reasonably achievable” should be used. The purpose of this study was to compare fluoroscopy times before and after the implementation of a protocol designed to reduce fluoroscopy usage during ureteroscopy. A retrospective review was conducted of 300 consecutive ureteroscopy patients at a single institution. Patients undergoing simple ureteroscopy without ancillary procedures or balloon dilation were further evaluated to determine the effect of a reduced fluoroscopy protocol. The protocol included several measures, including use of a laser-guided C-arm, use of a designated fluoroscopy technician and substitution of visual for fluoroscopic cues during ureteroscopy. Fluoroscopy times were compared between groups using a paired t test with P ⬍ .05 considered significant. Ureteroscopy cases before protocol implementation (n ⫽ 30) were compared with procedures after implementation (n ⫽ 30). Stone size and location were similar between groups. Protocol implementation significantly reduced the mean fluoroscopy exposure from 86.1 seconds (range 30-300) to 15.5 seconds (range 0-54; P ⬍ .001). There was no difference in mean operative time (74.2 vs 65.1 minutes; P ⫽ .14), or complications (2 patients vs 2 patients; P ⫽ 1) between groups. No complication in either group could be ascribed to the fluoroscopic technique. The reduced fluoroscopy protocol resulted in an 82% reduction in fluoroscopy time without altering patient outcomes. These simple radiation-reducing techniques add no technical difficulty and improve safety for the patient, surgeon, and operating room staff by lowering radiation exposure. UROLOGY 78: 286 –290, 2011. © 2011 Elsevier Inc.
F
luoroscopic imaging plays a crucial role during many routine minimally invasive procedures, including ureteroscopic lithotripsy.1 The increasing use of fluoroscopy has prompted the Food and Drug Administration to release a public health advisory educating physicians and patients of the need to limit radiation exposure to reduce potential negative effects of excessive radiation exposure.2 There is no known safe lower limit of radiation exposure below which the patient will experience no harmful effects. All ionizing radiation carries with it the potential to cause cancer.3 Thus, an increased use of radiation carries with it the potential to increase a patient or population’s risk for developing From the Department of Urology, Loma Linda University Medical Center, Loma Linda, California Reprint requests: D. Duane Baldwin, Department of Urology, Loma Linda University School of Medicine, 11234 Anderson Street, Room A560, Loma Linda, CA, 92354. E-mail: [email protected] Submitted: June 4, 2010; accepted (with revisions): November 14, 2010
286
© 2011 Elsevier Inc. All Rights Reserved
cancer.4 Whenever patients are exposed to radiation, a fundamental principle of radiation usage should be to decrease the exposure to the lowest dosage possible “as low as reasonably achievable” (ALARA).5 One of the major areas where urologists can control the administration of radiation is during fluoroscopic imaging. Fluoroscopy is used to diagnose and document the location of stones and filling defects during endoscopic cases, to ensure the safe passage of instruments and tools into the urinary tract, and to assist in renal mapping during endoscopy. Although the amount of radiation received from fluoroscopy during simple ureteroscopy may not be large compared with the dosages received from diagnostic modalities like computed tomography (CT) scanning or therapeutic purposes like cancer treatment, the effects of radiation are cumulative.6 In addition, the high-volume urologist who performs hundreds of endoscopic cases per year may be exposed to increased amounts of scattered radiation during these procedures. 0090-4295/11/$36.00 doi:10.1016/j.urology.2010.11.020
Table 1. Radiation-reducing measures Before Protocol Estimation of location of kidney and bladder visually Fluoroscopic guidance to confirm placement of guidewire and stent Review of imaging, without measurement of stone location with respect to bony landmarks Fluoroscopic confirmation of stone location Fluoroscopy without regard for respiratory motion Randomly assigned fluoroscopy technicians Fluoroscopic confirmation of stent bladder curl Retrograde pyelogram to look for filling defects in ureter Continuous fluoroscopy mode for portions of wire, stent, and scope positioning
Fluoroscopy-Reducing Protocol Use of laser guided C-arm Visual and tactile cues for guidewire and stent placement Detailed review of prior imaging, including identification of level of stone and distance from iliac crest and lumbar vertebrae Imaging present on high-definition screen in front of surgeon during case Activation timed with respiration Usage of designated fluoroscopy technician Visual confirmation of stent bladder curl with cystoscopy Visual confirmation of stone location with ureteroscopy Single pulse fluoroscopy mode for portions of wire, stent, and scope positioning
There are several potential techniques that could be used to decrease both patient and staff radiation exposure during ureteroscopic lithotripsy. Well-established techniques include the use of lead shielding, increasing the distance from the exposure source, and decreasing the kVp or mAs for the source. One of the simplest and most effective techniques to reduce radiation exposure is to decrease fluoroscopy time during endoscopic procedures, including ureteroscopy.5,7 In an attempt to minimize radiation exposure for patients and staff during ureteroscopy, a reduced fluoroscopy protocol was instituted in our center. The purpose of this study was to compare the fluoroscopy times and patient outcomes in ureteroscopy patients before and after the implementation of this reduced fluoroscopy protocol.
MATERIAL AND METHODS Institutional review board approval at Loma Linda University Medical Center was obtained for a retrospective analysis of 300 consecutive patients in a single institution who underwent endoscopic stone surgery between November 2006 and September 2009 by a single endoscopic surgeon. All patients underwent ureteroscopy and laser lithotripsy, with only the fluoroscopy technique varying between groups. Patients requiring ureteral balloon dilation, undergoing ancillary procedures, or with entombed stents or bladder stones were excluded from analysis. Patient demographics, stone size and location, body mass index (BMI), complications, operating time, and fluoroscopy time were obtained and compared between groups. Stone area was measured in the 2 largest dimensions. In January 2009, specific radiation-reducing measures were instituted in an attempt to decrease the fluoroscopy exposure for patients undergoing ureteroscopy (Table 1). Before implementing these measures, standard practice was to use fluoroscopy to identify the stone, place guidewires and the ureteroscope, and view the curl of the stent in the bladder and renal pelvis. Imaging was present on the computer, but not in direct view of the scrubbed surgeon. The new radiation-reducing measures started with a detailed review of prior imaging immediately before the start of a case to prevent excess imaging of nonessential areas. The imaging was present in front of the scrubbed UROLOGY 78 (2), 2011
surgeon on a high-definition monitor for the entire case. The stone location was identified with respect to the bony landmarks, including lumbar vertebrae and iliac crest. Films were then available throughout the case for referral if there were any doubts as to anatomy or stone location. A GE OEC 9900 Elite (General Electric Healthcare, Waukesha, WI) portable C-arm fluoroscopy machine was used, which was equipped with a laser pointer to aid in positioning the machine before activation of the beam (Fig. 1(A)). This allowed the correct positioning of the C-arm before activation and prevented the need to acquire additional images to center the beam on the area of interest. The C-arm activation was also timed with the patient’s respiration (end expiration) to minimize kidney movement and image distortion because this is the longest and most reproducible phase of the respiratory cycle.8 Visual cues were then sought on the static image preserved upon the monitor rather than viewing real-time fluoroscopic images. In each case, a designated fluoroscopy technician was used who was acquainted with the protocol goals and completely familiarized with the fluoroscopy machine usage and relevant urological anatomy. During passage of the guidewires, dual lumen catheter and/or ureteroscope, the surgeon made use of tactile cues and external visual cues as opposed to relying upon only fluoroscopic cues. Thus, fluoroscopic imaging was required only when an obstruction was felt or to confirm final placement in the kidney. Instead of acquiring fluoroscopic confirmation during placement of a second wire, the surgeon relied on tactile cues and inspection of the length of the wire compared with the wire currently in place (Fig. 1(B)). At the conclusion of the procedure, the stent was placed under direct cystoscopic visualization for the bladder coil, and a short fluoroscopy activation for placement of the renal coil. Renal mapping was performed by taking a single film of the contrast-filled renal collecting system to provide a road map. Calyces were then visually inspected, ensuring that the correct number and location of calyces had been endoscopically visualized rather than relying on real-time fluoroscopy. Fluoroscopic times, operative times, stone cross-sectional area, age, and BMI were compared before and after protocol implementation using a paired t-test. Categorical variables, such as gender, complications, stone-free rates, and repeat procedures were compared before and after protocol implementation using a Fisher’s exact test. In addition, a multivariate 287
Figure 1. (A). Laser-guided C-arm. (B) Comparing the length of the 2 wires for placement confirmation without the use of additional fluoroscopy. Table 2. Preoperative characteristics Before Protocol (n ⫽ 30) Mean age in years (range) Mean stone area in mm2 (range) Stone composition (%) Analysis not done Calcium oxalate Calcium phosphate Uric acid Cystine Other Gender M/F (%M/%F) Mean BMI in kg/m2 (range)
After Protocol (n ⫽ 30)
P Value
49.8 (27-69) 106.4 (12-500)
55.6 (26-88) 100.1 (12-349.1)
.11 .81
13 (43.3) 8 (26.7) 7 (23.3) 1 (3.3) 1 (3.3) 0 (0) 17/13 (56.7/43.3) 29.7 (19.8-45.5)
10 (33.3) 13 (43.3) 6 (20.0) 0 (0) 0 (0) 1 (3.3) 13/17 (43.3/56.7) 26.4 (18-41)
.31 .03
Table 3. Outcome characteristics
Mean fluoroscopy time in seconds (range) Mean operative time in minutes (range) No. complications (%) No. Stone-free patients (%) No. needed repeat procedure (%)
Before Protocol (n ⫽ 30)
After Protocol (n ⫽ 30)
P Value
86.1 (21.6-300) 74.2 (30-187) 2 (6.67) 25 (83.3) 2 (6.67)
15.5 (0-54) 65.1 (27-155) 2 (6.67) 25 (83.3) 2 (6.67)
⬍.01 .14 1.00 1.00 1.00
regression analysis was used to control for confounding factors. Statistics were run in SPSS version 16 (SPSS, Inc., Chicago, IL) and a P value ⬍ 0.05 was considered significant.
RESULTS The mean age of all patients was 52.7 years (range 26-88 years) and mean BMI was 28.1 kg/m2 (range 18-45.5 kg/m2). Sixty ureteroscopic surgeries were identified that did not include stones in multiple locations, bladder stones, entombed stents, steinstrasse, or ureteral balloon dilation. Thirty ureteroscopic cases were analyzed before protocol implementation, and 30 cases were compared 288
after protocol implementation (Table 2). The mean fluoroscopy time was 86.1 seconds before implementation and 15.5 seconds (P ⬍ .001) after protocol implementation (Table 3). A multivariable regression analyzed fluoroscopy time against age, BMI, operative time, and stone cross-sectional area. No significant confounders were observed between fluoroscopy time and these dependent variables. In addition, age (P ⫽ .56), operative time (P ⫽ .14), stone area (P ⫽ .96), and complications (P ⫽ 1.00) were similar between the 2 groups. The BMI was greater for the group before protocol 29.7 vs 26.4 (P ⫽ .03) but did UROLOGY 78 (2), 2011
not affect fluoroscopy time when analyzed in the multivariate regression analysis (P ⫽ .62). There were 2 complications in the first group and 2 in the second (P ⫽ 1.00). In both the standard fluoroscopy protocol and the reduced fluoroscopy protocol, the complications included 1 case of sepsis and urinary tract infection in each group. No complications appeared to be related to fluoroscopic imaging technique. Similar stonefree rates were seen in each group (83% vs 83% and P ⫽ 1.00). The number of retreatments required in each group was also the same, with 2 (7%) in each group (P ⫽ 1.00). There was no significant difference in stone chemical composition between the groups (Table 2).
COMMENT In urology, fluoroscopic imaging plays a major role in endoscopic surgery. Current American Urological Association guidelines recommend ureteroscopy as a first-line treatment for symptomatic ureteral calculi.9 Further increasing the use of ureteroscopy, data from the National Health and Nutrition Examination Survey indicate that a lifetime prevalence of kidney stones in the United States is greater than 5% and this number is increasing.10 The cause of this increase in stone prevalence is unknown but possibly linked to an increased rate of obesity, decreased calcium intake, or better stone detection.10,11 This translates into an 83% increase in the number of ureteroscopies performed in the United States from 1994 to 2004.12 Fluoroscopic imaging is used extensively during ureteroscopy to direct placement of guidewires, locate stones, monitor ureteral dilation, perform renal mapping, and place ureteral stents. As application of ureteroscopic techniques increases, the radiation exposure of patients and staff members will also increase. This study demonstrates that the measures instituted in the reduced fluoroscopy protocol were effective in reducing the fluoroscopy time and thereby the radiation dose to the patient, surgeon, and staff. Before protocol implementation, the mean fluoroscopy time was 89.5 seconds. This value is similar to the 78-second fluoroscopy time previously reported during uncomplicated ureteroscopy by Hellawell and colleagues.13 After protocol implementation, however, the time was reduced to 15.5 seconds. This represents an 82% reduction in fluoroscopy time and consequently a proportional reduction in radiation exposure. This radiation reduction was accomplished with minimal additional effort or technical procedural modification. The reduced fluoroscopy protocol did not increase the subjective complexity of the case. Importantly, our study demonstrates that the reduced radiation protocol did not increase surgical complexity, operative time, residual stone rates, or complication rates. The risks of ionizing radiation can be divided into 2 categories: deterministic and stochastic.3 Deterministic effects are those for which a threshold exists above which damage will be apparent, and as the dose increases, so UROLOGY 78 (2), 2011
does the severity of the injury. Several of these types of injuries are documented in various fields, especially cardiology.14,15 Some of these injuries include skin erythema, ulcers, telangiectasia, and dermal atrophy.14 Yet it appears that fluoroscopic imaging during ureteroscopy for stone treatment results in radiation levels below those required for deterministic effects.7,13 In contrast, theoretically the stochastic effects lack a threshold of injury. Cancer is an example of a stochastic injury that may be induced at any radiation dose, but the probability increases with increased dose.3 In fact, it is estimated that 5695 (0.9%) cases of cancer in the United States each year occur because of medically-imposed ionizing radiation.4 To decrease this theoretical risk of cancer and other stochastic effects, the principle of ALARA should be observed and the lowest possible radiation dosage used that will allow the safe completion of the procedure. Although fluoroscopy for ureteroscopy uses a relatively low dose of radiation, the cumulative effects can pose a theoretical risk of cancer. Hellawell determined that surgeons received a mean of 11.6 Gy per urological case.13 Although this individual dose is low, when one considers that high-volume surgeons may perform up to 500 cases per year, this would result in 5.8 mGy per year. This is more than half of the effective dose of a noncontrast CT scan of the abdomen. When factored over a surgeon’s 30-year career, this would be equal to 174 mGy, equal to the effective radiation dose of more than 17 noncontrast abdominal CT scans or 8700 chest x-rays.16 Ionizing radiation has the potential to cause leukemia, lymphomas, and various other solid cancers.6 Certainly, any effort that would reduce radiation exposure for the staff and patient without compromising patient outcomes would be desirable. In an effort to understand and reduce radiation exposure to patients, several fields of medicine have examined their use of fluoroscopy.17,18 An orthopedic study attempted a fluoroscopy-reducing protocol that included a laser-guided C-arm and found a 32% reduction in fluoroscopic time.19 To the best of our knowledge, our study appears to be the first to use these specific modifications to a reduced radiation protocol for ureteroscopic laser lithotripsy. One possible limitation of this study is that it is retrospective and patients were not randomized. Based on the initial success with this reduced fluoroscopy protocol, it was felt that a prospective study would not be ethical. Another limitation of this study is that specific radiation exposures were not determined, but rather relative amounts were compared using fluoroscopy time. In each patient, the mAs and kVp setting were not recorded. Some have argued that fluoroscopy time is not a good marker of radiation exposure.20,21 Certainly, the radiation dose is affected by patient size and hence skin dosages will be higher in obese compared with thin patients. Yet, fluoroscopy time is a major determinant of a patient’s individual radiation dose.7 Thus, if one were 289
to reduce an individual’s fluoroscopy time, the radiation dose would concurrently be reduced. At present, we are also developing reduced mA and kVp protocols to further limit radiation dose in patients. Another possible limitation of the study was the difference in BMI between groups. This difference did not affect fluoroscopy time, as was demonstrated in the multivariate analysis. The preliminary results in this study suggest that major reductions could be made in radiation exposure during fluoroscopy without compromising patient outcome. Certainly, these results will need to be confirmed in other centers. Fluoroscopic imaging during ureteroscopy is an integral part of endoscopic surgery, which allows safe and effective treatment. It is vital that, as reduced fluoroscopy protocols are developed, measures are taken to ensure that patient outcomes are not compromised. It is possible that with future developments in endourology, other techniques will further reduce or even completely remove radiation exposure during endoscopic cases. Until that time, urological surgeons should adhere to the principles of ALARA in an attempt to reduce the radiation dose for the safety of their patients, staff, and themselves.
CONCLUSIONS This reduced fluoroscopy protocol resulted in an 82% reduction in fluoroscopy time without altering patient outcomes. These simple radiation-reducing techniques add no technical difficulty to the case and may improve procedure safety for the patient, surgeon, and operating room staff. References 1. Miller DL. Overview of contemporary interventional fluoroscopy procedures. Health Phys. 2008;95:638. 2. US Food and Drug Administration. Public Health Advisory: Avoidance of serious X-Ray Induced Skin Injuries to patients during Fluoroscopically Guided procedures. 1994. 3. Mahesh M. Fluoroscopy: patient radiation exposure issues. RadioGraphics. 2001;21:1033. 4. Berrington de Gonzalez A, Darby S. Risk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries. Lancet. 2004; 363:345.
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5. Mantu-Gupta MMCO, Jay MD, Shah B, et al. Percutaneous management of the Upper Urinary Tract. In: Alan M, Wein J. Wien: Campbell-Walsh Urology, 9th ed. Philadelphia: Saunders Elsevier, 2007. 6. Yoshinaga S, Mabuchi K, Sigurdson AJ, et al. Cancer risks among radiologists and radiologic technologists: review of epidemiologic studies. Radiology. 2004;233:313. 7. Bagley DH, Cubler-Goodman A. Radiation exposure during ureteroscopy. J Urol. 1990;144:1356. 8. Chang JY, Balter P, Komaki R. Image-guided stereotactic body radiation therapy for early-stage non-small cell lung cancer. In: Cox JD, Chang JY, Komaki R. Image-Guided Radiotherapy of Lung Cancer. New York: Informa HealthCare, 2007. 9. Preminger GM, Tiselius HG, Assimos DG, et al. Guideline for the management of ureteral calculi. J Urol. 2007;178:2418. 10. Stamatelou KK, Francis ME, Jones CA, et al. Time trends in reported prevalence of kidney stones in the United States: 19761994. Kidney Int. 2003;63:1817. 11. Goldfarb DS. Increasing prevalence of kidney stones in the United States. Kidney Int. 2003;63:1951. 12. Bratslavsky G, Moran ME. Current trends in ureteroscopy. Urol Clin North Am. 2004;31:181. 13. Hellawell GO, Mutch SJ, Thevendran G, et al. Radiation exposure and the urologist: what are the risks? J Urol. 2005;174:948. 14. Koenig TR, Wolff D, Mettler FA, et al. Skin injuries from fluoroscopically guided procedures: part 1, Characteristics of radiation injury. AJR Am J Roentgenol. 2001;177:3. 15. Shope TB. Radiation-induced skin injuries from fluoroscopy. RadioGraphics. 1996;16:1195. 16. Shrimpton PC Hillier MC, Lewis MA, et al. Doses From Computed Tomography (CT) Examinations in the UK: 2003 Review. NRPBW67. Chilton: NRPB; 2005. 17. Papaioannou S, Afnan M, Coomarasamy A, et al. Long term safety of fluoroscopically guided selective salpingography and tubal catheterization. Hum Reprod. 2002;17:370. 18. Perisinakis K, Theocharopoulos N, Damilakis J, et al. Estimation of patient dose and associated radiogenic risks from fluoroscopically guided pedicle screw insertion. Spine. 2004;29:1555. 19. Proschek D, Kafchitsas K, Rauschmann MA, et al. Reduction of radiation dose during facet joint injection using the new image guidance system SabreSource: a prospective study in 60 patients. Eur Spine J. 2009;18:546. 20. Balter S. Capturing patient doses from fluoroscopically based diagnostic and interventional systems. Health Phys. 2008;95:535. 21. Taylor JB, Selzman KA. An evaluation of fluoroscopic times and peak skin doses during radio frequency catheter ablation and biventricular internal cardioverter defibrillator implant procedures. Health Phys. 2009;96:138.
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