Ultrasound Guided Ureteroscopy for the Definitive Management of Ureteral Stones: A Randomized, Controlled Trial Levi A. Deters,* Lawrence M. Dagrosa, Benjamin W. Herrick, Anne Silas and Vernon M. Pais, Jr.† From the Section of Urology, Department of Surgery and Department of Radiology (AS), Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire

Abbreviations and Acronyms BMI ¼ body mass index Accepted for publication June 19, 2014. Study received institutional review board approval. * Correspondence: Section of Urology, Department of Surgery, Dartmouth Hitchcock Medical Center, One Medical Center Dr., Lebanon, New Hampshire 03756 (FAX: 509-7470020; e-mail: [email protected]). † Financial interest and/or other relationship with Clinical Nephrology.

Purpose: Ureteroscopy is central to the surgical management of ureteral stones. Fluoroscopy is conventionally used for intraoperative guidance, although there is growing effort to decrease the exposure of patients and staff to ionizing radiation. We developed a radiation-free approach to ureteroscopy using ultrasound guidance to manage ureteral stones. To our knowledge we present the first randomized trial to study its safety and efficacy. Materials and Methods: This single center, randomized clinical trial from 2011 to 2013 enlisted patients who presented with symptomatic ureteral stones 8 mm or less without a significant ipsilateral stone burden. Patients were randomly assigned to ultrasound or fluoroscopic guided ureteroscopy after temporizing ureteral stent placement. Intraoperative ultrasound guidance was performed using real-time imaging with the transducer placed at the patient flank to visualize the collecting system of the ipsilateral kidney. We compared operative time, stone size, stone-free status and complication rates between the 2 groups. Results: A total of 50 patients were enrolled in study with 25 per arm. There was no difference in stone size (5.9 vs 5.7 mm), patient age (56 vs 52 years) or body mass index (31 vs 30 kg/m2) in the test group compared to controls. The ultrasound guidance cohort showed no significant difference in the stone-free rate (86% vs 86%) or the complication rate (8% vs 16%) compared to controls. Operative time was no longer in the ultrasound guidance cohort. Conclusions: In this feasibility study we found that ureteral stones may be definitively managed in a timely, effective and safe fashion without ionizing radiation in the general population using this novel technique of ultrasound guided ureteroscopy. Key Words: ureter; urolithiasis; ultrasonography; radiation, ionizing; ureteroscopy

THE prevalence of urolithiasis is steadily increasing with an estimated 1 of 11 people in the United States affected1 at an annual cost of more than 2 billion dollars.2 Ureteroscopy remains one of the first line treatments for definitive management of ureteral stones.3 Conventional ureteroscopy relies on intraoperative




fluoroscopy4 for visualization and guidance, exposing the patient, surgeon and operating room staff to ionizing radiation. There is increasing awareness and concern about the clinical use of ionizing radiation and the need to decrease exposure to patients and medical professionals is understood.


http://dx.doi.org/10.1016/j.juro.2014.06.073 Vol. 192, 1710-1713, December 2014 Printed in U.S.A.


To minimize the hazards of ionizing radiation there has been a trend toward alternative imaging modalities. Ultrasound provides an excellent alternative for upper urinary tract imaging because it is radiation free, rapid and portable, and allows for excellent visualization of the renal pelvis and calyces. We previously reported using ultrasound guided ureteroscopy in pregnant patients, in whom fluoroscopy is to be minimized or avoided when possible.5 In this feasibility study we applied this radiation-free technique of ultrasound guided ureteroscopy to the general population to manage ureteral stones in a safe, effective manner without ionizing radiation.

MATERIALS AND METHODS Subjects and Study Design After obtaining institutional review board approval we enrolled 50 adult patients in this study who had been previously stented for a symptomatic ureteral stone 8 mm or less. The study was powered a priori to detect a 20-minute difference in operative time between the 2 groups since operative time is the primary expense associated with this procedure.6 We excluded from analysis patients with a greater than 2 mm ipsilateral renal stone burden and patients undergoing simultaneous urological procedures. Patients were randomized preoperatively by sealed envelope technique to standard fluoroscopic (control) vs ultrasound guided (test group) ureteroscopy. For test cases a C-arm was available in the operating room if adequate visualization could not be achieved with ultrasound. The variables assessed were patient age, gender, BMI, stone size, stone location, fluoroscopy time, operative time and stone-free rate. In all patients a ureteral stent was placed after stone clearance and removed within 14 days postoperatively. Followup at 4 to 6 weeks included plain x-ray of the kidneys, ureters and bladder, and renal ultrasound to assess for residual stone burden and screen for silent obstruction. Stone-free was defined as the lack of radiographic evidence of residual stones on postoperative imaging. Complications were defined as repeat hospital admission, emergency room visits or unplanned intervention in the 2-month postoperative period.

Surgical Technique Only patients who had been previously stented were included in study. All patients in each group underwent semirigid ureteroscopy and flexible pyeloscopy using a standardized technique and active fragment retrieval. Stents were identified cystoscopically, grasped and withdrawn to the meatus. A 0.035-inch guidewire was placed through the stent if possible, or beside it if encrustation did not permit passing the wire in coaxial fashion. Guidewire position in the renal pelvis was confirmed by fluoroscopy in controls and by real-time ultrasound with the transducer placed against the patient flank in the test group. Semirigid ureteroscopy was performed and all identified distal stones were fragmented with laser lithotripsy.


In the control group after ureteral stone clearance a flexible ureteroscope was advanced to the renal pelvis and contrast medium was instilled to opacify the collecting system. Each calyx was systematically inspected for residual fragments and fluoroscopy was used to confirm that all calyces were examined. Any residual stone was extracted. In the test group flexible ureteroscopy was performed in similar fashion but real-time ultrasound was used to verify that all calyces were inspected. All identified stones were extracted at that time. According to our institutional review board approved protocol a ureteral stent was temporarily placed in all patients due to concern for ureteral inflammation and edema after instrumentation. Appropriate positioning of the proximal curl in the renal pelvis was confirmed by fluoroscopy in the control group and by real-time ultrasound in the test group. An OECÒ 9100 C-arm with pulsed fluoroscopy and low dose settings was used in all control cases. Real-time ultrasound in the test group was performed with radiology technician assistance using a CX50 Compact Ultrasound Unit with a C5-1 Broadband Curved Array Transducer (Philips Ultrasound, Bothell, Washington) with an extended operating frequency range.

Efficacy and Safety Assessment Before study initiation a data safety monitoring board was formed. The data were periodically reviewed, including complication rates and stone-free outcomes.

Statistical Analysis Patient age, BMI, stone size, fluoroscopy time, operative time and the stone-free rate were compared between the cohorts using the independent 2-sample t-test. Post hoc power analysis was performed on operative time. The Fisher exact test was used to compare complication rates. Complications were classified according to the Clavien grading system.

RESULTS A total of 50 patients were enrolled in study with 25 per arm. Average stone size in the test group was 5.9 mm compared to 5.6 mm in controls (p ¼ 0.557). Age and BMI were similar in the groups. The upper tract was visualized in all test cases under ultrasound guidance, including wire, scope and stent placement (see figure). Operative time was no longer in the ultrasound guided cohort than in the traditional fluoroscopy group (average 36.52 vs 45.7 minutes). Each cohort had an 86% stone-free rate as defined by no residual stone fragments on followup x-ray and ultrasound (p ¼ 0.99). There were 2 complications in the test group compared with 4 in the control group, of which all were Clavien grade I or II. Clot retention developed in a test patient, requiring bladder irrigation in the emergency department. Another patient was hospitalized with renal colic after accidentally removing a tethered stent prematurely. Two controls required hospital admission, including



Intraoperative ultrasound shows safety wire (a), ureteroscope (b) and ureteral stent (c)

1 for pyelonephritis and 1 for stent pain. Another 2 patients were treated as outpatients for urinary tract infection (see table).

DISCUSSION Medical imaging is the largest man-made radiation exposure source in the general population.7 Ionizing radiation exposure has been increasing in the United States with a noted sevenfold increase in radiation due to medical imaging in the last 30 years.8 There is increasing awareness of the morbidity of ionizing radiation exposure to patients, operating room staff and surgeons in terms of cataracts,9 malignancy potential10 and the occupational hazards of wearing protective lead during the procedure, such as chronic neck and lower back pain.11 The medical community is challenged to minimize ionizing radiation when applicable. Patient characteristics and outcomes

Av age Av BMI (kg/m2) Av stone size (mm) Av fluoroscopy time (secs) Av operative time (mins) % Stone-free % Complications



p Value

56.04 31.12 5.9 Not applicable 36.52 86 8

52.44 29.89 5.6 23.95 45.72 86 16

0.392 0.473 0.557 e 0.04 0.992 0.161

While urolithiasis continues to increase in incidence and prevalence, the question arises of whether there is a way to minimize radiation in our diagnosis and treatment of these patients. We identified ureteroscopy as a procedure that is amenable to a radiation-free approach. Several methods were previously suggested to decrease the radiation dose associated with ureteroscopy, including low dose and pulse fluoroscopy, or visual and tactile cues to guide ureteroscopy while limiting fluoroscopy to confirming stent placement.12 Intraoperative ultrasound guidance has gained popularity in the urological literature to obviate the need for ionizing radiation. This approach was described for percutaneous nephrolithotomy13 as well as for ureteral stent placement14 and ureteroscopy5 in pregnant patients in whom fluoroscopy is to be minimized or avoided if possible. We report equivalent stone-free rate and complication rates using ultrasound guided ureteroscopy and the conventional fluoroscopic technique for definitive management of ureteral stones. Our average fluoroscopy time per case was 23.95 seconds in the control group. This is below the average reported range, which in a 2013 report was estimated to be 144 seconds.12 The mean radiation dose in controls was 5.47 mGy. While this dose is small, with the recurrent nature of stone disease


and the frequency with which urologists and staff perform these procedures any reduction in radiation exposure is desirable. We found a minimal cost difference between the modalities with ultrasound guidance costing $13.97 more per hour at our institution. This increased cost reflects the radiology technologist fee at our institution. Besides being radiation free, we noted several benefits to the ultrasound guided approach to ureteroscopy. Continuous intraoperative monitoring of the collecting system allows for real-time verification of guidewire, scope and stent placement, and obviates the need for single snapshot fluoroscopy. Many urologists have significant experience with ultrasound and in our experience this modality was also easily adaptable and intuitive to the residents involved. We expect that this technique would be easily translated to the pediatric population, considering the generally favorable body habitus of this group. With that said, while there was concern that this technique may not be applicable to obese patients, in the test cohort the average BMI was 31.2 kg/m2 (range 23.3 to 43.6). We found no difference in stone-free outcomes, operative times or complication rates based on BMI in this group. Mean operative time was shorter in the ultrasound guided cohort than in the standard fluoroscopic guided cohort (36.52 vs 45.72 minutes). It is possible that the real-time visualization provided by the ultrasonographer obviates the need to pause for image capture and fluoroscope repositioning, which may have decreased total operative time in the ultrasound group. However, due to our relatively


small sample size the statistical power of this difference was low (p ¼ 0.56 with a 95% CI). A larger sample size would be required to prove whether ultrasound guidance operative time is shorter but we can confidently say that in our study it was no longer. There are several limitations to our study. We attempted to minimize variation between the 2 arms as much as possible. Therefore, our study was limited to a single surgeon experience with prestented patients who had a relatively small stone burden. We also did not use ureteral access sheaths in this study since we do not routinely use them for ureteral stones less than 8 mm in prestented patients. However, we have used access sheaths while performing ultrasound guided ureteroscopy in the pregnant population and found that when the wire location is confirmed in the renal pelvis, tactile feedback is as useful as fluoroscopy for safely passing the sheath. Our study size was small and was powered to show a 20-minute difference in operative time but not in other factors, such as stone-free and complication rates. However, we believe that this series serves as a pilot study for larger investigations and broader applications.

CONCLUSIONS Our prospective, randomized, controlled study verified that ureteral stones can be managed in a safe, effective and radiation-free manner by ultrasound guided ureteroscopy. Larger studies are warranted to assess the widespread applicability of this technique.

REFERENCES 1. Scales CD, Smith AC, Hanley JM et al: Prevalence of kidney stones in the United States. Eur Urol 2012; 62: 160. 2. Lotan Y: Economics and cost of care with stone disease. Adv Chronic Kidney Dis 2009; 16: 5. 3. Preminger GM, Tiselius HG, Assimos DG et al: Guideline for the management of ureteral calculi. J Urol 2007; 178: 2418. 4. Nascimento R, Coleman J and Solomon S: Current and future imaging for urologic interventions. Curr Opin Urol 2008; 18: 116. 5. Deters LA, Belanger G, Shah O et al: Ultrasound guided ureteroscopy in pregnancy. Clin Nephrol 2013; 79: 118. 6. Litwin MS, Sacher SJ and Cohen WS: The resource-based relative value scale: methods,

results and impacts on urology. J Urol 1993; 150: 981. 7. United Nations Scientific Committee on the Effects of Atomic Radiation: Sources and Effects of Ionizing Radiation. New York: United Nations 2000. 8. Ionizing Radiation Exposure of the Population of the United States. National Council on Radiation Protection Report 160. Bethesda: National Council on Radiation Protection and Measurements 2009. 9. Kleiman N: Radiation Cataract. New Insights on Risk and Basic Safety Standards. Brussels: European Commission 2007; pp 81e95. 10. Wenzel TB: Increased brain cancer risk in physicians with high radiation exposure. Radiology 2005; 235: 709.

11. Klein LW, Miller DL, Balter S et al: Occupational health hazards in the interventional laboratory: time for a safer environment. J Vasc Interv Radiol 2009; 20: 147. 12. Hsi RS and Harper JD: Fluoroless ureteroscopy: zero-dose fluoroscopy during ureteroscopic treatment of urinary-tract calculi. J Endourol 2013; 27: 432. 13. Basiri A, Ziaee SA, Nasseh H et al: Totally ultrasonography-guided percutaneous nephrolithotomy in the flank position. J Endourol 2009; 22: 1453. 14. Jarrard DJ, Gerber GS and Lyon ES: Management of acute ureteral obstruction in pregnancy utilizing ultrasound-guided placement of ureteral stents. Urology 1993; 42: 263.

Ultrasound guided ureteroscopy for the definitive management of ureteral stones: a randomized, controlled trial.

Ureteroscopy is central to the surgical management of ureteral stones. Fluoroscopy is conventionally used for intraoperative guidance, although there ...
370KB Sizes 0 Downloads 5 Views