I migliori abstracts sulla calcolosi, scelti per voi dal vostro

Marco Puglisi


Hemostatic Plug: Novel Technique for Closure of Percutaneous Nephrostomy Tract

Journal of Endourology. -Not available-, ahead of print.

Joel E. Abbott, DO,1 Arman Cicic, DO,1 Roger W. Jump III, DO,1 and Julio G. Davalos, MD2

1Department of Urology, Michigan State University, St. John Providence Health, Warren, Michigan.
2Department of Urology, University of Maryland, Chesapeake Urology Associates, Glen Burnie, Maryland.


Percutaneous nephrolithotomy (PCNL) is a standard treatment for patients with large or complex kidney stones. The procedure has traditionally included postoperative placement of a nephrostomy tube to allow for drainage and possible reentry. This practice was first implemented after complications incurred after tubeless PCNL in a small patient population. Recently, tubeless PCNL has reemerged as a viable option for selected patients, resulting in decreased pain and analgesic use, shorter hospitalization, quicker return to normal activity, and decreased urine extravasation. Gelatin matrix sealants are occasionally used in nephrostomy tract closure. Techniques for delivery of these agents have been ill described, and placement may be performed with varying results. We present a literature review comparing tubeless PCNL to its traditional variant with indications for use of each, as well as a comparison of agents used in closure.
Finally, we outline a novel, reproducible technique for closure of the dilated percutaneous renal access tract.


A Novel Device to Prevent Stone Fragment Migration During Percutaneous Lithotripsy

Journal of Endourology. -Not available-, ahead of print.

Justin I. Friedlander, MD,1 Jodi A. Antonelli, MD,1 Heather Beardsley, PhD,2 Stephen Faddegon, MD,1 Monica S.C. Morgan, MD,1 Jeffrey C. Gahan, MD,1 Margaret S. Pearle MD, PhD,1 and Jeffrey A. Cadeddu, MD1

1Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas.
2Department of Engineering, University of Texas Arlington, Arlington, Texas.


Purpose: We developed a novel device to capture stones in vivo in an enclosed bag (PercSac) to prevent dispersion of stone fragments during percutaneous nephrolithotomy (PCNL) or cystolitholapaxy. We report on our initial feasibility trials of the PercSac device.

Materials and Methods: PercSac consists of a specially designed polyethylene bag that is fitted over the shaft of a rigid nephroscope.
The bag is used to first entrap the target stone, then tighten around it to allow fragmentation within the bag. Matched pairs of 10 canine bladder stones (2.5 cm maximum diameter) were fragmented in a human bladder model using the CyberWand™ (Olympus America, Inc.), and the procedure was assessed for markers of efficiency and effectiveness.

Results: Median time to entrap the stone within the PercSac was 67 seconds (range 51–185 sec). Median time for stone fragmentation was significantly shorter with the PercSac than without (182.0 sec [range 108–221] vs 296.5 sec [range 226–398], P=0.004). Overall, however, there was no significant difference in the total time to entrap and fragment the stones between the two groups. A stone-free state was not achieved for any trial without the PercSac, while 9 of 10 trials with the PercSac resulted in a stone-free state.

Conclusions: Use of the PercSac in conjunction with stone fragmentation has the potential to reduce the occurrence of residual fragments after PCNL or cystolitholapaxy. Further in vitro testing in a kidney model is planned.


Totally Tubeless Versus Standard Percutaneous Nephrolithotomy for Renal Stones: Analysis of Clinical Outcomes and Cost

Journal of Endourology. -Not available-, ahead of print.

Sae Woong Choi, MD, Kang Sup Kim, MD, Jeong Ho Kim, MD, Yong Hyun Park, MD, PhD, Woong Jin Bae, MD, PhD, Sung-Hoo Hong, MD, PhD, Ji Youl Lee, MD, PhD, Sae Woong Kim, MD, PhD, Tae-Kon Hwang, MD, PhD, and Hyuk Jin Cho, MD, PhD
Department of Urology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.


Purpose: To evaluate the safety and cost-effectiveness of a totally tubeless percutaneous nephrolithotomy (PCNL) by comparing the clinical outcomes and cost analysis between standard PCNL and totally tubeless PCNL for renal stones.

Patients and Methods: From June 2012 to September 2013, a total of 121 patients with renal stones who underwent totally tubeless or standard PCNL by two experienced surgeons were retrospectively evaluated by group. According to the surgeon’s preference for the nephrostomy tube and/or ureteral stent, the present study was designed to be divided into Group 1 and Group 2. Group 1 was performed by one surgeon (H.J. Cho) who preferred a totally tubeless PCNL and Group 2 was performed by the other surgeon (S.H. Hong) who preferred a standard PCNL. We excluded bilateral renal stones, multiple approach, whole staghorn calculi, and previous renal surgery. Patient and stone characteristics, intraoperative and postoperative parameters, and cost analysis were compared between the two groups.

Results: There were no significant differences in the patient demographics between groups. Mean stone burden was 501.5±361.1 mm2 in Group 1 versus 535.2±353.1 mm2 in Group 2 (P=0.651). Length of hospital stay (1.72±0.58 v 4.10±1.88 days, P<0.001), postoperative pain scores using a visual analog scale (day 0: P<0.001, day 1: P=0.002), and analgesia requirements (33.2±21.3 v 45.2±19.5 mg, P=0.005) for Group 1 versus Group 2 showed significant differences. The stone-free rate was 86.4% versus 89.8% in Group 1 and Group 2, respectively (P=0.609). There were no significant differences in overall complications between groups (P=0.213). Mean total medical treatment costs in Groups 1 and 2 were 2398.22±549.1 USD and 2845.70±824.2 USD, respectively (P=0.002).

Conclusions: Many clinical outcomes in the totally tubeless PCNL showed comparable or better results than standard PCNL. We believe that totally tubeless PCNL is an acceptable, safe, and cost-effective alternative to standard PCNL for the treatment of renal stones.


Percutaneous Nephrolithotomy in Patients with Urinary Tract Abnormalities

Journal of Endourology. -Not available-, ahead of print.

Philippe D. Violette, MD, CM, Marie Dion, MD, Thomas Tailly, MD, John D. Denstedt, MD, and Hassan Razvi, MD Department of Surgery, Division of Urology, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada.


Background and Purpose: Patients with urinary tract abnormalities are at an increased risk of stone formation. Percutaneous nephrolithotomy (PCNL) plays an important role in the treatment of this patient population; however, outcomes are less well defined compared with patients with normal urinary tract anatomy. Our objective was to evaluate the influence of urinary tract abnormalities on intraoperative and postoperative outcomes with PCNL.

Patients and Methods: We report on a single-center prospective database of 2284 consecutive PCNLs in 1935 patients from 1990 to 2012.
For the purposes of this analysis, patients were categorized by the presence or absence of a urinary tract abnormality. Multivariable analyses were used to identify independent predictors of the length of hospital stay, operative time, complications, and residual stones at discharge and 3 months.

Results: A urinary tract abnormality was present in 14.4% (n=330) of the cohort. On univariable analysis, patients with urinary tract abnormalities were more likely to present with urinary tract infection (28% vs 19%, P<0.001) and less likely to present with hematuria (13% vs 19%, P<0.02). On multivariable regression, a urinary tract abnormality was predictive of residual stone at discharge, need for a secondary procedure, but did not increase the risk of residual stone at 3 months or the development of complications. Operative time and hospital stay were only moderately prolonged.

Conclusion: Patients with urinary tract abnormalities who undergo PCNL have a higher risk of residual stones at discharge and need for secondary procedures, but comparable complication rates, operative time, and hospital stay.


Do We Really Need Kidneys-Ureters-Bladder Radiography to Predict Stone Radiopacity Before Treatment with Shockwave Lithotripsy? Development and Internal Validation of a Novel Predictive Model Based on Computed Tomography Parameters

Journal of Endourology. -Not available-, ahead of print.

Stavros Sfoungaristos, MD, Guy Hidas, MD, Ofer N. Gofrit, MD, PhD, Vladimir Yutkin, MD, Arie Latke, Ezekiel H. Landau, MD, Dov Pode, MD, and Mordechai Duvdevani, MD
Urology Department, Hadassah University Hospital, The Hebrew University, Jerusalem, Israel.


Purpose: To produce and validate a predictive model based on CT parameters for calculating the probability of a stone to be visible on fluoroscopy of shockwave lithotripsy (SWL) and to compare its accuracy to that of kidneys-ureters-bladder (KUB) radiography.

Methods: We retrospectively analyzed 306 patients (sample group) who underwent an SWL between March 2011 and August 2012. A multivariate analysis of several parameters extracted from the preoperative CT scan was conducted to identify independent predictors for radiopacity on SWL fluoroscopy. The results were used for the creation of a predictive model. Internal validation was made on a group of 75 patients (validation group) treated from September 2012 until December 2012. Predictive accuracy of the model was evaluated by receiver operating characteristic (ROC) curve and calibration plot. The ROCcurve was also used for comparing the predictive accuracy of the model to that of KUB radiography.

Results: From 306 evaluated stones, 238 (77.8%) were visible on fluoroscopy. Results of the multivariate analysis revealed that stone size (P<0.001), stone attenuation (P<0.001), location in the midureter (P<0.001), the distance between the stone and the anterior abdominal wall (P<0.001), and fat thickness of the anterior abdominal wall (P=0.001) were all independent predictors for stone radiopacity on fluoroscopy. A predictive model was produced based on the above parameters. The model demonstrated high calibration and areas under the curve of 0.923 and 0.965 in the sample and validation group, respectively, while its predictive performance was significantly higher (P<0.001) of that of KUB radiography (area under the curve=0.727). Conclusions: This novel model can estimate with high accuracy stone radiopacity on SWL fluoroscopy using parameters of CT scan and thus it can be used as an alternative to KUB radiography for treatment planning.


Clinical Outcomes After Ureteroscopic Lithotripsy in Patients Who Initially Presented with Urosepsis: Matched Pair Comparison with Elective Ureteroscopy

Journal of Endourology. -Not available-, ahead of print.


Ramy F. Youssef, MD, Andreas Neisius, MD, Zachariah G. Goldsmith, MD, Momin Ghaffar, BS, Matvey Tsivian, MD, Richard H. Shin, MD, Fernando Cabrera, MD, Michael N. Ferrandino, MD, Charles D. Scales, MD, Glenn M. Preminger, MD, and Michael E. Lipkin, MD

Division of Urology, Comprehensive Kidney Stone Center, Duke University Medical Center, Durham, North Carolina.


Background and Purpose: The outcomes of ureteroscopy (URS) after urgent decompression and antibiotics for patients who initially present with urosepsis because of obstructive urolithiasis have not been previously evaluated. The aim of this study was to compare the outcomes and complications of URS in patients with a recent history of sepsis with those without sepsis.

Methods: The study included 138 patients who underwent URS for stone removal from January 2004 to September 2011 at a university medical center. A matched-pair analysis was performed using three parameters (age, sex, and race) to compare outcomes and complications between 69 patients who had sepsis vs a matched cohort who did not have sepsis before URS.

Results: The study included 138 patients, 88 (64%) females and 50 (36%) males with a median age of 57.5 years (range 18–88 years). Patients with previous sepsis had similar patient characteristics and stone-free rates (81% vs 77%) compared with patients without previous sepsis (P>0.05). Patients with previous sepsis, however, had a significantly higher complications rate (20% vs 7%), longer hospital length of stay (LOS), and longer courses of postoperative antibiotics after URS (P<0.05). Sepsis developed postoperatively in two patients with diabetes (one with and one without previous sepsis), and postoperative fever developed in five patients with previous sepsis.

Conclusions: URS after decompression for urolithiasis-related sepsis has similar success but higher complication rates, greater LOS, and longer course of postoperative antibiotics. This is important in counseling patients who present for definitive URS after urgent decompression for urolithiasis-related sepsis.


The Impact of Ureteral Stent Type on Patient Symptoms as Determined by the Ureteral Stent Symptom Questionnaire: A Prospective, Randomized, Controlled Study

Journal of Endourology. -Not available-, ahead of print.

Hyoung Keun Park, MD, PhD,1 Sung Hyun Paick, MD, PhD,1 Hyeong Gon Kim, MD, PhD,1 Yong Soo Lho, MD, PhD,1 and Sangrak Bae, MD2

1Department of Urology, Konkuk University School of Medicine, Seoul, Republic of Korea.
2Department of Urology, The Catholic University of Korea, Uijeongbu St. Mary’s Hospital, Uijeongbu, Republic of Korea.


Purpose: To minimize stent-related symptoms, the proximal part of the Polaris™ stent is composed of a firm material and its distal part is composed of a soft material. The aim of this study was to compare stent-related symptoms of Polaris and Percuflex® stents and to assess the impacts of these stents on quality of life.

Patients and Methods: A total of 144 patients were randomized to a “test” group (Polaris; n=64) or a “conventional” group (Percuflex; n=80) at the time of ureteral stent insertion after ureteroscopic stone removal surgery. Stents were allocated using a randomization program. At 1 week postoperatively, patient symptoms were evaluated using the Ureteral Stent Symptom Questionnaire (USSQ), and patients were asked complete a 10 cm visual analogue scale (VAS). Mean scores for USSQ domains and mean VAS scores were compared.

Results: Mean patient age was 50.3 years, and the male-to-female ratio was 1:0.85. No significant intergroup differences were found in the domain scores of urinary symptoms (P=0.58), pain (P=0.87), general health (P=0.20), work (P=0.24), sexual activity (P=0.64), or additional problems (P=0.24). In addition, VAS scores were nonsignificantly different (P=0.11). Analysis of USSQ item scores, however, revealed the test group had better results for “presence of pain,” “frequency of pain killer use,” “difficulties with respect to hard physical activity,” “fatigue,” “frequency of rest,” “stent-related impact on work,” “antibiotics use” than the conventional group except for “outpatient department visits”.

Conclusion: Compared with the conventional Percuflex ureteral stent, the new Polaris ureteral stent with a soft tail was not found to offer significant advantages in terms of voiding symptoms, pain, general health, sexual matters, or additional problems as determined by the USSQ or in VAS determined pain. Sub-analysis, however, showed that the Polaris has some advantages with respect to pain, physical activities, impact on work, and additional problems. Accordingly, the soft-tipped Polaris stent was found to have some clinical advantages over the conventional Percuflex stent.


Cystine Stones: A Single Tertiary Center Experience

Journal of Endourology. -Not available-, ahead of print.

Rony Hakim, MD,2,* Ran Katz, MD,1 Ofer N. Gofrit, MD, PhD,1 Ezekiel H. Landau, MD,1 Vladimir Yutkin, MD,1 Dov Pode, MD,1 and Mordechai Duvdevani, MD1

1Urology Department, Hadassah University Hospital, the Hebrew University, Jerusalem, Israel.
2Hadassah School of Medicine, the Hebrew University, Jerusalem, Israel.


Objective: To analyze the epidemiological and clinical characteristics and therapeutic outcomes of patients with cystine stones and to compare them with the characteristics of patients with calcium oxalate stones.

Patients and Methods: We identified 30 patients with cystine stones who were consulted in our department from January 1972 until December 2013. These patients were matched and paired, based on age and gender, to 30 calcium oxalate stone formers who were diagnosed and treated in our department from January 2011 until December 2013.

Results: Cystine stones were significantly large in size (p<0.001) and most of them were found in the kidney (p=0.002). Patients with cystinuria had their first stone episode at an early age (p<0.001) compared with patients with calcium oxalate stones. No significant differences were observed regarding the frequency and the severity of symptoms. Both groups had similar visits per year in outpatient clinics, emergency room admissions, and episodes of febrile urinary tract infections. Cystine stone formers had undergone significantly higher number of procedures for stone removal (p<0.001). No statistical differences were found in the compliance rates between the groups. Patients with cystine stones had significantly higher serum creatinine levels (p=0.005).

Conclusions: Cystine stones present in an earlier age and have the likelihood to be large in size. Patients with cystine stones undergo a greater number of procedures, and they have a greater risk to develop chronic renal impairment.


A Comparison of Antegrade Percutaneous and Laparoscopic Approaches in
the Treatment of Proximal Ureteral Stones

BioMed Research International
Volume 2014 (2014), Article ID 691946, 5 pages


Hikmet Topaloglu,1 Nihat Karakoyunlu,1 Sercan Sari,1 Hakki Ugur Ozok,1 Levent Sagnak,1 and Hamit Ersoy21Urology Clinic, Diskapi Yildirim Beyazit Training and Research Hospital, 06310 Ankara, Turkey
2Department of Urology, Hitit University Faculty of Medicine, 19030 Corum, Turkey


Purpose. To compare the effectiveness and safety of retroperitoneal laparoscopic ureterolithotomy (RLU) and percutaneous antegrade ureteroscopy (PAU) in which we use semirigid ureteroscopy in the treatment of proximal ureteral stones.

Methods. Fifty-eight patients with large, impacted stones who had a history of failed shock wave lithotripsy (SWL) and, retrograde ureterorenoscopy (URS) were included in the study between April 2007 and April 2014. Thirty-seven PAU and twenty-one RLU procedures were applied. Stone-free rates, operation times, duration of hospital stay, and follow-up duration were analyzed.

Results. Overall stone-free rate was 100% for both groups.There was no significant difference between both groups with respect to postoperative duration of hospital stay and urinary leakage of more than 2 days. PAU group had a greater amount of blood loss (mean hemoglobin drops for PAU group and RLU group were 1.6 ± 1.1 g/dL versus 0.5 ± 0.3 g/dL, resp.; P = 0.022). RLU group had longer operation time (for PAU group and RLU group 80.1 ± 44.6 min versus 102.1 ± 45.5 min, resp.; P = 0.039).

Conclusions. Both PAU and RLU appear to be comparable in the treatment of proximal ureteral stones when the history is notable for a failed retrograde approach or SWL.The decision should be based on surgical expertise and availability of surgical equipment.


A Giant Case of Pyonephrosis Resulting from Nephrolithiasis

Case Reports in Urology
Volume 2014 (2014), Article ID 161640, 3 pages


Ali Erol,1 Soner Çoban,2 and Ali Tekin31Department of Urology, Medical Park Hospital, Istanbul, Turkey
2Department of Urology, Sevket Yilmaz Education and Research Hospital, Yildirim, Bursa, Turkey
3Department of Urology, Duzce University School of Medicine, Duzce, Turkey


Pyonephrosis is an uncommon disease that is associated with suppurative destruction of the renal parenchyma in adults. Upper urinary tract infection and obstruction play a role in its etiology. Immunosuppression from medications (steroids), diseases (diabetes mellitus, AIDS), and anatomic variations (pelvic kidney, horseshoe kidney) may also be risk factors for pyonephrosis. Fever, shivering, and flank pain are frequent clinical symptoms. On physical examination, a palpable abdominal mass may be associated with the hydronephrotic kidney. Septic shock and death can occur if the disorder is not treated with urgent surgery. After the acute phase, most patients are treated with nephrectomy. In this paper, we share the etiology, clinical features, diagnosis and treatment of pyonephrosis using the background of a case with giant pyonephrosis developing due to a kidney stone, the most common cause of upper urinary tract obstruction.


AUA Kidney Stone Guidelines Unveiled

Renal and Urology News June 2014

Jody A. Charnow, Editor


ORLANDO—The American Urological Association (AUA) announced at its annual meeting the development of its first guidelines for the medical management of kidney stones.

Margaret S. Pearle, MD, PhD, who chaired the panel that reviewed the available evidence that formed the basis of the guidelines, summarized the recommendations in a presentation at the AUA’s 2014 annual meeting.

In discussing the rationale for the new guidelines, Dr. Pearle noted that kidney stones are a common problem with a high rate of recurrence, and despite effective and established treatment regimens for medical management, evidence suggests that medical management is underused. Additionally, she said, management of patients with recurrent stones lacks uniformity.

The guidelines contain 27 statements that fall broadly into the categories of evaluation, diet therapies, pharmacologic therapies, and follow-up. All patients diagnosed with a stone should have a screening evaluation that consists of dietary intake, medical therapies, serum chemistries, urinalysis, and urine culture, said Dr. Pearle, professor of urology and internal medicine at the University of Texas Southwestern Medical Center in Dallas. The evaluation is aimed at identifying medical conditions associated with stone formation, such as primary hyperparathyroidism or type 2 diabetes, dietary aberrations, such as low or high calcium intake or excessive intake of animal protein, or medications such as topiramate, she told listeners.

Serum chemistries should be obtained to define underlying conditions that may be associated with recurrent stones, such as primary hyperparathyroidism or distal renal tubule acidosis. Measuring serum parathyroid hormone is considered an optional study that should be obtained only if primary hyperparathyroidism is suspected, Dr. Pearle said.

In addition, Dr. Pearle stated that “a stone analysis should be obtained at least once if a stone is available because knowledge of stone composition can implicate certain underlying etiologies, such as a low urine pH in patients with uric acid stones.”

Metabolic testing should be performed in high-risk or interested first-time stone formers as well as in recurrent stone formers, she said. Metabolic testing should consist of one or preferably two 24-hour urine collections obtained under random diet. These urine collections should be analyzed for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine. “The 24-hour urine is then used to guide recommendations regarding dietary measures and medication.”

The guidelines also recommend that:

All stone formers should be advised to drink enough fluids to achieve a urine volume of at least 2.5 liters daily.
Patients with calcium stones and high urinary calcium should be advised to limit their sodium intake and to consume the recommended daily allowance of calcium of 1,000 to 1,200 mg daily.
Patients with uric acid stones and calcium stones and high urinary uric acid should be advised to limit their intake of non-dairy animal protein. About 30% of urinary uric acid is derived from dietary purine intake, and animal protein accounts for most purine intake, Dr. Pearle noted.
Patients with high urinary calcium and recurrent calcium stones should be offered thiazide diuretics because these medications act directly on the distal renal tubule and indirectly at the proximal renal tubule to promote renal calcium reabsorption.
Patients with recurrent calcium stones and low urinary citrate should be offered potassium citrate because this medication provides an alkali load that promotes a citraturic response and increases urinary inhibitory activity.
Patients with recurrent calcium stones and who have hyperuricosuria should be offered allopurinol.
Thiazide diuretics and/or potassium citrate should be offered to patients with recurrent calcium stones in whom no metabolic abnormality is identified or in whom appropriate metabolic abnormalities have been addressed but stone formation persists. Allopurinol should not routinely be offered as first-line therapy to patients with uric acid stones. Uric acid nephrolithiasis is primarily a disease of urinary acidification, and at a pH greater than 6 to 6.5, most uric acid will be found in its soluble or dissociated form, and even high amounts of uric acid at these higher urinary pHs will be fully solublized, Dr. Pearle explained.

Dr. Pearle concluded her talk by mentioning the importance of follow-up. “Success in gauged by improvement in urinary stone risk factors and ultimately by reduction in stone formation,” she said. Serial urine collections must be obtained to address changes in urinary risk factors.


Ultrasonic Propulsion of Kidney Stones: Interview with Jonathan Harper, MD

Delicia Honen Yard

Renal and Urology News August 2014


Imagine a noninvasive treatment for renal calculi that does not shatter the stones but instead employs low-intensity, ultrasound-generated pulses to move them to and through the ureter.

Principal investigator Jonathan Harper, MD, assistant professor in the Department of Urology at the University of Washington (UW) School of Medicine in Seattle, explains to Renal & Urology News how he and his collaborators are turning their “Rolling Stones” concept into a feasible office procedure.

What do you call the low-power ultrasound device you are using in your studies?

Dr. Harper: We call the procedure ultrasonic propulsion. In the FDA application we called the device Propulse 1. Casually around UW, we refer to our work and our group as Rolling Stones. If this becomes a startup company, we like the name Sonomotion.

How does the device/intervention work?

Dr. Harper: Generally, sound waves are focused on the stone and they transfer momentum to the stone, which makes it move. Specifically, it looks like a diagnostic ultrasound machine with an ultrasound image. The user puts the probe against the skin and visualizes the stone and kidney, touches the image of the stone on the screen, and watches the stone move. Touching the screen sends the focused wave to the stone without interrupting imaging.

What inspired you to develop this process and device?

Dr. Harper: [Senior principal engineer and adjunct assistant professor of urology] Michael Bailey and others in the UW Applied Physics Laboratory have worked on shock wave lithotripsy (SWL) for a long time. Stones are fragmented with SWL, but often these pieces remain in areas of the kidney and do not pass. Many have wanted to find a way to help those pieces pass.

We knew ultrasound could be used to create a pushing force, and so applied that to this problem. Ultrasound engineers use the force to calibrate instruments. In our case we tried to use focused ultrasound to break stones like lithotripsy, but ended up moving the stones and had to chase them around a water tank.

Why do you think ultrasonic propulsion could be successful?

Dr. Harper: It is a practical solution to a real problem. The design and operation are pretty simple and elegant. We know the forces we can generate and have a good feel for the forces that are required. The outputs to achieve these forces have been shown to be safe and not cause pain. We have had success in multiple preliminary studies and are now performing the first clinical trial.

There also has been enthusiasm from many expert endourologists throughout the country, which is encouraging. In addition, we have had many patients contact us with questions and [express] interest in volunteering as subjects.

Approximately 300 urologists visited the hands-on demonstration [conducted at the 2013 annual meeting of the American Urological Association (AUA)], and all survey respondents marked [that they would be] “likely” or “very likely” to use the technology. They had the chance to use the system to reposition stones in a mannequin or to drive the stone through a maze. [The group will be demonstrating the procedure again at the May 2014 AUA annual meeting in Orlando, Florida.—Eds.]

What advantages does low-power ultrasound have over extracorporeal SWL and such other treatments for kidney stones as flexible ureteroscopy and percutaneous nephrolithotomy?

Dr. Harper: Ultrasonic propulsion serves a different purpose. Most stones are small enough to pass naturally; however, many of them ultimately require surgery. Any of the above-mentioned surgeries breaks the stone into fragments that either pass naturally or remain in the kidney. These fragments may slowly grow and ultimately require another surgery.

The goal of our technology is to help the small stones or residual fragments pass by moving them out of the calyx and closer to the UPJ [ureteropelvic junction] or ureter. In turn, we would expect to avoid some surgeries and improve the outcomes of others.

There are other possible scenarios of moving a stone that would be of benefit, such as dislodging a large stone obstructing the UPJ. This could not only relieve a patient’s pain and obstruction, but also could avoid an urgent procedure and allow for scheduling an elective surgery.

Moving a stone before or during surgery could facilitate access to a hard-to-reach stone. Other uses are [related to] diagnostic feedback—for example, by inducing movement, one might be able to tell that two stones next to each other are in fact two stones and not one.

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