Removal of Small, Asymptomatic Kidney Stones and Incidence of Relapse.

BACKGROUND: The benefits of removing small (≤6 mm), asymptomatic kidney stones endoscopically is unknown. Current guidelines leave such decisions to the urologist and the patient. A prospective study involving older, nonendoscopic technology and some retrospective studies favor observation. However, published data indicate that about half of small renal stones left in place at the time that larger stones were removed caused other symptomatic events within 5 years after surgery. METHODS: We conducted a multicenter, randomized, controlled trial in which, during the endoscopic removal of ureteral or contralateral kidney stones, remaining small, asymptomatic stones were removed in 38 patients (treatment group) and were not removed in 35 patients (control group). The primary outcome was relapse as measured by future emergency department visits, surgeries, or growth of secondary stones. RESULTS: After a mean follow-up of 4.2 years, the treatment group had a longer time to relapse than the control group (P<0.001 by log-rank test). The restricted mean (±SE) time to relapse was 75% longer in the treatment group than in the control group (1631.6±72.8 days vs. 934.2±121.8 days). The risk of relapse was 82% lower in the treatment group than the control group (hazard ratio, 0.18; 95% confidence interval, 0.07 to 0.44), with 16% of patients in the treatment group having a relapse as compared with 63% of those in the control group. Treatment added a median of 25.6 minutes (interquartile range, 18.5 to 35.2) to the surgery time. Five patients in the treatment group and four in the control group had emergency department visits within 2 weeks after surgery. Eight patients in the treatment group and 10 in the control group reported passing kidney stones. CONCLUSIONS: The removal of small, asymptomatic kidney stones during surgery to remove ureteral or contralateral kidney stones resulted in a lower incidence of relapse than nonremoval and in a similar number of emergency department visits related to the surgery. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the Veterans Affairs Puget Sound Health Care System; ClinicalTrials.gov number, NCT02210650.).

Fragmentation of Stones by Burst Wave Lithotripsy in the First 19 Humans.

PURPOSE: We report stone comminution in the first 19 human subjects by burst wave lithotripsy (BWL), which is the transcutaneous application of focused, cyclic ultrasound pulses. MATERIALS AND METHODS: This was a prospective multi-institutional feasibility study recruiting subjects undergoing clinical ureteroscopy (URS) for at least 1 stone ≤12 mm as measured on computerized tomography. During the planned URS, either before or after ureteroscope insertion, BWL was administered with a handheld transducer, and any stone fragmentation and tissue injury were observed. Up to 3 stones per subject were targeted, each for a maximum of 10 minutes. The primary effectiveness outcome was the volume percent comminution of the stone into fragments ≤2 mm. The primary safety outcome was the independent, blinded visual scoring of tissue injury from the URS video. RESULTS: Overall, median stone comminution was 90% (IQR 20, 100) of stone volume with 21 of 23 (91%) stones fragmented. Complete fragmentation (all fragments ≤2 mm) within 10 minutes of BWL occurred in 9 of 23 stones (39%). Of the 6 least comminuted stones, likely causative factors for decreased effectiveness included stones that were larger than the BWL beamwidth, smaller than the BWL wavelength or the introduction of air bubbles from the ureteroscope. Mild reddening of the papilla and hematuria emanating from the papilla were observed ureteroscopically. CONCLUSIONS: The first study of BWL in human subjects resulted in a median of 90% comminution of the total stone volume into fragments ≤2 mm within 10 minutes of BWL exposure with only mild tissue injury.

First Series Using Ultrasonic Propulsion and Burst Wave Lithotripsy to Treat Ureteral Stones.

PURPOSE: Our goal was to test transcutaneous focused ultrasound in the form of ultrasonic propulsion and burst wave lithotripsy to reposition ureteral stones and facilitate passage in awake subjects. MATERIALS AND METHODS: Adult subjects with a diagnosed proximal or distal ureteral stone were prospectively recruited. Ultrasonic propulsion alone or with burst wave lithotripsy was administered by a handheld transducer to awake, unanesthetized subjects. Efficacy outcomes included stone motion, stone passage, and pain relief. Safety outcome was the reporting of associated anticipated or adverse events. RESULTS: Twenty-nine subjects received either ultrasonic propulsion alone (n = 16) or with burst wave lithotripsy bursts (n = 13), and stone motion was observed in 19 (66%). The stone passed in 18 (86%) of the 21 distal ureteral stone cases with at least 2 weeks follow-up in an average of 3.9±4.9 days post-procedure. Fragmentation was observed in 7 of the burst wave lithotripsy cases. All subjects tolerated the procedure with average pain scores (0-10) dropping from 2.1±2.3 to 1.6±2.0 (P = .03). Anticipated events were limited to hematuria on initial urination post-procedure and mild pain. In total, 7 subjects had associated discomfort with only 2.2% (18 of 820) propulsion bursts. CONCLUSIONS: This study supports the efficacy and safety of using ultrasonic propulsion and burst wave lithotripsy in awake subjects to reposition and break ureteral stones to relieve pain and facilitate passage.

Virtual Reality Warm-up Before Robot-assisted Surgery: A Randomized Controlled Trial.

TRIAL DESIGN: This was a randomized controlled trial. BACKGROUND: Intraoperative errors correlate with surgeon skill and skill declines with intervals of inactivity. The goals of this research were to identify the optimal virtual reality (VR) warm-up curriculum to prime a surgeon's technical skill and validate benefit in the operating room. MATERIALS AND METHODS: Surgeons were randomized to receive six trial sessions of a designated set of VR modules on the da Vinci Skills Simulator to identify optimal VR warm-up curricula to prime technical skill. After performing their curricula, warm-up effect was assessed based on performance on a criterion task. The optimal warm-up curriculum was chosen from the group with the best task time and video review-based technical skill. Robot-assisted surgery-experienced surgeons were then recruited to either receive or not receive warm-up before surgery. Skill in the first 15 min of surgery was assessed by blinded surgeon and crowdworker review as well as tool motion metrics. The intervention was performing VR warm-up before human robot-assisted surgery. Warm-up effect was measured using objective performance metrics and video review using the Global Evaluative Assessment of Robotic Skills tool. Linear mixed effects models with a random intercept for each surgeon and nonparametric modified Friedman tests were used for analysis. RESULTS: The group performing only a Running Suture task on the simulator was on average 31.3 s faster than groups performing other simulation tasks and had the highest Global Evaluative Assessment of Robotic Skills scores from 41 surgeons who participated. This was chosen as the optimal curriculum. Thereafter, 34 surgeons completed 347 surgeries with corresponding video and tool motion data. No statistically significant differences in skill were observed with the warm-up intervention. CONCLUSIONS: We conclude that a robotic VR warm-up before performing the early stages of surgery does not impact the technical skill of the surgeon.

Burst wave lithotripsy and acoustic manipulation of stones.

PURPOSE OF REVIEW: Burst wave lithotripsy and ultrasonic propulsion of kidney stones are novel, noninvasive emerging technologies to separately or synergistically fragment and reposition stones in an office setting. The purpose of this review is to discuss the latest refinements in technology, to update on testing of safety and efficacy, and to review future applications. RECENT FINDINGS: Burst wave lithotripsy produced consistent, small passable fragments through transcutaneous applications in a porcine model, while producing minimal injury and clinical trials are now underway. A more efficient ultrasonic propulsion design that can also deliver burst wave lithotripsy effectively repositioned 95% of stones in 18 human participants (18 of 19 kidneys) and clinical trials continue. Acoustic tractor beam technology is an emerging technology with promising clinical applications through the manipulation of macroscopic objects. SUMMARY: The goal of the reviewed work is an office-based system to image, fragment, and reposition urinary stones to facilitate their natural passage. The review highlights progress in establishing safety, effectiveness, and clinical benefit of these new technologies. The work is also anticipating challenges in clinical trials and developing the next generation of technology to improve on the technology as it is being commercialized today.

National Imaging Trends after Percutaneous Nephrolithotomy.

PURPOSE: Followup imaging after percutaneous nephrolithotomy serves to detect postoperative complications, residual fragments and silent hydronephrosis. However, the timing and optimal imaging modality remain poorly defined. We describe imaging use patterns after percutaneous nephrolithotomy. MATERIALS AND METHODS: In the MarketScan® database we identified patients 17 to 64 years old who underwent percutaneous nephrolithotomy between 2007 and 2014. Imaging modalities were identified by CPT, and ICD-9 and 10 codes, and tracked for 1 year after percutaneous nephrolithotomy. The modalities included computerized tomography, renal ultrasound, abdominal x-ray and intravenous pyelogram. Cumulative longitudinal use patterns were characterized and the association with demographic factors was assessed by the chi-square test. RESULTS: Of the 6,495 patients included in analysis 29% and 15% had undergone no postoperative imaging by 3 and 12 months, respectively. While abdominal x-ray was the most common modality at 3, 6 and 12 months, performed in 46%, 53% and 62% patients, respectively, nearly 50% underwent computerized tomography by 1 year. Of these patients 34% underwent computerized tomography within 3 months, which was done within the first 3 days in 69%. During the study period renal ultrasound use increased by 13% while computerized tomography and abdominal x-ray use remained relatively stable. Female gender, residence in the Northeast, no health maintenance organization status and treatment in a metropolitan statistical area were independently associated with higher rates of renal ultrasound on multivariate analyses (p <0.05). CONCLUSIONS: Among insured adults national imaging patterns vary following percutaneous nephrolithotomy. Many patients do not receive any followup imaging while approximately half undergo computerized tomography within a year. Imaging patterns may be evolving with the increased use of ultrasound.

Retrospective comparison of measured stone size and posterior acoustic shadow width in clinical ultrasound images.

PURPOSE: Posterior acoustic shadow width has been proposed as a more accurate measure of kidney stone size compared to direct measurement of stone width on ultrasound (US). Published data in humans to date have been based on a research using US system. Herein, we compared these two measurements in clinical US images. METHODS: Thirty patient image sets where computed tomography (CT) and US images were captured less than 1 day apart were retrospectively reviewed. Five blinded reviewers independently assessed the largest stone in each image set for shadow presence and size. Shadow size was compared to US and CT stone sizes. RESULTS: Eighty percent of included stones demonstrated an acoustic shadow; 83% of stones without a shadow were ≤ 5 mm on CT. Average stone size was 6.5 ± 4.0 mm on CT, 10.3 ± 4.1 mm on US, and 7.5 ± 4.2 mm by shadow width. On average, US overestimated stone size by 3.8 ± 2.4 mm based on stone width (p < 0.001) and 1.0 ± 1.4 mm based on shadow width (p < 0.0098). Shadow measurements decreased misclassification of stones by 25% among three clinically relevant size categories (≤ 5, 5.1-10, > 10 mm), and by 50% for stones ≤ 5 mm. CONCLUSIONS: US overestimates stone size compared to CT. Retrospective measurement of the acoustic shadow from the same clinical US images is a more accurate reflection of true stone size than direct stone measurement. Most stones without a posterior shadow are ≤ 5 mm.

First in Human Clinical Trial of Ultrasonic Propulsion of Kidney Stones.

PURPOSE: Ultrasonic propulsion is a new technology using focused ultrasound energy applied transcutaneously to reposition kidney stones. We report what are to our knowledge the findings from the first human investigational trial of ultrasonic propulsion toward the applications of expelling small stones and dislodging large obstructing stones. MATERIALS AND METHODS: Subjects underwent ultrasonic propulsion while awake without sedation in clinic, or during ureteroscopy while anesthetized. Ultrasound and a pain questionnaire were completed before, during and after propulsion. The primary outcome was to reposition stones in the collecting system. Secondary outcomes included safety, controllable movement of stones and movement of stones less than 5 mm and 5 mm or greater. Adverse events were assessed weekly for 3 weeks. RESULTS: Kidney stones were repositioned in 14 of 15 subjects. Of the 43 targets 28 (65%) showed some level of movement while 13 (30%) were displaced greater than 3 mm to a new location. Discomfort during the procedure was rare, mild, brief and self-limited. Stones were moved in a controlled direction with more than 30 fragments passed by 4 of the 6 subjects who had previously undergone a lithotripsy procedure. The largest stone moved was 10 mm. One patient experienced pain relief during treatment of a large stone at the ureteropelvic junction. In 4 subjects a seemingly large stone was determined to be a cluster of small passable stones after they were moved. CONCLUSIONS: Ultrasonic propulsion was able to successfully reposition stones and facilitate the passage of fragments in humans. No adverse events were associated with the investigational procedure.

Use of the Acoustic Shadow Width to Determine Kidney Stone Size with Ultrasound.

PURPOSE: Ultrasound is known to overestimate kidney stone size. We explored measuring the acoustic shadow behind kidney stones combined with different ultrasound imaging modalities to improve stone sizing accuracy. MATERIALS AND METHODS: A total of 45 calcium oxalate monohydrate stones were imaged in vitro at 3 different depths with the 3 different ultrasound imaging modalities of conventional ray line, spatial compound and harmonic imaging. The width of the stone and the width of the acoustic shadow were measured by 4 operators blinded to the true size of the stone. RESULTS: Average error between the measured and true stone width was 1.4 ± 0.8 mm, 1.7 ± 0.9 mm, 0.9 ± 0.8 mm for ray line, spatial compound and harmonic imaging, respectively. Average error between the shadow width and true stone width was 0.2 ± 0.7 mm, 0.4 ± 0.7 mm and 0.0 ± 0.8 mm for ray line, spatial compound and harmonic imaging, respectively. Sizing error based on the stone width worsened with greater depth (p <0.001) while the sizing error based on the shadow width was independent of depth. CONCLUSIONS: Shadow width was a more accurate measure of true stone size than a direct measurement of the stone in the ultrasound image (p <0.0001). The ultrasound imaging modality also impacted the measurement accuracy. All methods performed similarly for shadow size while harmonic imaging was the most accurate stone size modality. Overall 78% of the shadow sizes were accurate to within 1 mm, which is similar to the resolution obtained with clinical computerized tomography.

Coronary Artery Calcium Score and Association with Recurrent Nephrolithiasis: The Multi-Ethnic Study of Atherosclerosis.

PURPOSE: Subclinical coronary artery calcification is an established predictor of cardiovascular events. While a history of kidney stones has been linked to subclinical carotid atherosclerosis, to our knowledge no study has examined its relationship with coronary artery calcification. We studied the association between kidney stone history and prevalent coronary artery calcification in MESA (Multi-Ethnic Study of Atherosclerosis). MATERIALS AND METHODS: MESA is a multisite cohort study of participants 45 to 84 years old without known cardiovascular disease at baseline from 2000 to 2002. Computerized tomography was done in 3,282 participants at followup in 2010 to 2012 to determine coronary artery calcification and kidney stone history was assessed by self-report. Coronary artery calcification scores were categorized as none-0, mild-1 to 99, moderate-100 to 399 or severe-400 or greater. Cross-sectional analysis was performed adjusting for demographic and dietary factors related to kidney stones. RESULTS: The prevalence of kidney stone disease history was approximately 9%, mean ± SD participant age was 69.5 ± 9.3 years, 39% of participants were Caucasian, 47% were men and 69% had detectable coronary artery calcification (score greater than 0). No difference in the score was seen between single stone formers and nonstone formers. Recurrent kidney stone formation was associated with moderate or severe calcification on multivariable logistic regression vs none or mild calcification (OR 1.80, 95% CI 1.22-2.67). When coronary artery calcification scores were separated into none, mild, moderate and severe calcification, recurrent stone formation was associated with a higher score category on multivariable ordinal logistic regression (OR 1.44 per category, 95% CI 1.04-2.01). CONCLUSIONS: Recurrent kidney stone formation is associated with subclinical coronary atherosclerosis. This association appeared stronger with coronary artery calcification severity than with coronary artery calcification presence.

Fournier's Gangrene: Epidemiology and Outcomes in the General US Population.

PURPOSE: Case series reported 20-40% mortality rates for patients with Fournier's gangrene with some series as high as 88%. This literature comes almost exclusively from referral centers. MATERIALS AND METHODS: We identified and analyzed inpatients with Fournier's gangrene who had a surgical debridement or died in the US State Inpatient Databases. RESULTS: One thousand six hundred and forty one males and 39 females with Fournier's gangrene represented <0.02% of hospital admissions. Overall, the incidence was 1.6 cases per 100,000 males and case fatality was 7.5%. Sixty six percent of hospitals cared for no cases per year, 17% cared for 1 case per year, 10% cared for 2 cases per year, 4% cared for 3 cases per year, 1% cared for 4 cases per year, and only 1% cared for ≥5 cases per year. Teaching hospitals had higher mortality (adjusted OR 1.9) due primarily to more acutely ill patients. Hospitals treating more than 1 Fournier's gangrene case per year had an adjusted 42-84% lower mortality (p < 0.0001). CONCLUSIONS: Most hospitals rarely care for Fournier's gangrene patients. The population-based mortality rate (7.5%) was substantially lower than the case series from tertiary care centers. Hospitals that treated more number of Fournier's gangrene patients had lower mortality rates, thereby supporting the rationale that regionalized care worked well for patients with this rare disease.

Physical activity, energy intake and the risk of incident kidney stones.

PURPOSE: Recent data suggest that higher physical activity and lower energy intake may be associated with a lower risk of kidney stones. To our knowledge whether these associations could be reproduced in other study populations after accounting for life-style and dietary factors is not known. MATERIALS AND METHODS: We analyzed data on 3 large prospective cohorts, including HPFS, and NHS I and II. Information was collected by validated biennial questionnaires. The HR of incident stones in participants in different categories of physical activity and energy intake was assessed by Cox proportion hazards regression adjusted for age, body mass index, race, comorbidity, medication, calcium supplement use, fluid and nutrient intake. RESULTS: Analysis included 215,133 participants. After up to 20 years of followup 5,355 incident cases of kidney stones occurred. On age adjusted analysis higher levels of physical activity were associated with a lower risk of incident kidney stones in women (NHS I and II) but not in men. However, after multivariate adjustment there was no significant association between physical activity and kidney stone risk in HPFS, and NHS I and II (highest vs lowest category HR 1.00, 95% CI 0.87-1.14, p for trend = 0.94, HR 1.01, 95% CI 0.85-1.19, p for trend = 0.88 and HR 1.03, 95% CI 0.90-1.18, p for trend = 0.64, respectively). Energy intake was not associated with stone risk (multivariate adjusted p for trend ≥0.49). CONCLUSIONS: In 3 large prospective cohorts there was no independent association between physical activity and energy intake, and the incidence of symptomatic kidney stones.

Fragmentation of urinary calculi in vitro by burst wave lithotripsy.

PURPOSE: We developed a new method of lithotripsy that uses short, broadly focused bursts of ultrasound rather than shock waves to fragment stones. We investigated the characteristics of stone comminution by burst wave lithotripsy in vitro. MATERIALS AND METHODS: Artificial and natural stones (mean ± SD size 8.2 ± 3.0 mm, range 5 to 15) were treated with ultrasound bursts using a focused transducer in a water bath. Stones were exposed to bursts with focal pressure amplitude of 6.5 MPa or less at a 200 Hz burst repetition rate until completely fragmented. Ultrasound frequencies of 170, 285 and 800 kHz were applied using 3 transducers, respectively. Time to fragmentation for each stone type was recorded and fragment size distribution was measured by sieving. RESULTS: Stones exposed to ultrasound bursts were fragmented at focal pressure amplitudes of 2.8 MPa or greater at 170 kHz. Fractures appeared along the stone surface, resulting in fragments that separated at the surface nearest to the transducer until the stone was disintegrated. All natural and artificial stones were fragmented at the highest focal pressure of 6.5 MPa with a mean treatment duration of 36 seconds for uric acid stones to 14.7 minutes for cystine stones. At a frequency of 170 kHz the largest artificial stone fragments were less than 4 mm. Exposure at 285 and 800 kHz produced only fragments less than 2 mm and less than 1 mm, respectively. CONCLUSIONS: Stone comminution with burst wave lithotripsy is feasible as a potential noninvasive treatment method for nephrolithiasis. Adjusting the fundamental ultrasound frequency allows for stone fragment size to be controlled.

Targeted microbubbles: a novel application for the treatment of kidney stones.

Kidney stone disease is endemic. Extracorporeal shockwave lithotripsy was the first major technological breakthrough where focused shockwaves were used to fragment stones in the kidney or ureter. The shockwaves induced the formation of cavitation bubbles, whose collapse released energy at the stone, and the energy fragmented the kidney stones into pieces small enough to be passed spontaneously. Can the concept of microbubbles be used without the bulky machine? The logical progression was to manufacture these powerful microbubbles ex vivo and inject these bubbles directly into the collecting system. An external source can be used to induce cavitation once the microbubbles are at their target; the key is targeting these microbubbles to specifically bind to kidney stones. Two important observations have been established: (i) bisphosphonates attach to hydroxyapatite crystals with high affinity; and (ii) there is substantial hydroxyapatite in most kidney stones. The microbubbles can be equipped with bisphosphonate tags to specifically target kidney stones. These bubbles will preferentially bind to the stone and not surrounding tissue, reducing collateral damage. Ultrasound or another suitable form of energy is then applied causing the microbubbles to induce cavitation and fragment the stones. This can be used as an adjunct to ureteroscopy or percutaneous lithotripsy to aid in fragmentation. Randall's plaques, which also contain hydroxyapatite crystals, can also be targeted to pre-emptively destroy these stone precursors. Additionally, targeted microbubbles can aid in kidney stone diagnostics by virtue of being used as an adjunct to traditional imaging methods, especially useful in high-risk patient populations. This novel application of targeted microbubble technology not only represents the next frontier in minimally invasive stone surgery, but a platform technology for other areas of medicine.

Activity, energy intake, obesity, and the risk of incident kidney stones in postmenopausal women: a report from the Women's Health Initiative.

Obesity is a strong risk factor for nephrolithiasis, but the role of physical activity and caloric intake remains poorly understood. We evaluated this relationship in 84,225 women with no history of stones as part of the Women's Health Initiative Observational Study, a longitudinal, prospective cohort of postmenopausal women enrolled from 1993 to 1998 with 8 years' median follow-up. The independent association of physical activity (metabolic equivalents [METs]/wk), calibrated dietary energy intake, and body mass index (BMI) with incident kidney stone development was evaluated after adjustment for nephrolithiasis risk factors. Activity intensity was evaluated in stratified analyses. Compared with the risk in inactive women, the risk of incident stones decreased by 16% in women with the lowest physical activity level (adjusted hazard ratio [aHR], 0.84; 95% confidence interval [95% CI], 0.74 to 0.97). As activity increased, the risk of incident stones continued to decline until plateauing at a decrease of approximately 31% for activity levels ≥10 METs/wk (aHR, 0.69; 95% CI, 0.60 to 0.79). Intensity of activity was not associated with stone formation. As dietary energy intake increased, the risk of incident stones increased by up to 42% (aHR, 1.42; 95% CI, 1.02 to 1.98). However, intake <1800 kcal/d did not protect against stone formation. Higher BMI category was associated with increased risk of incident stones. In summary, physical activity may reduce the risk of incident kidney stones in postmenopausal women independent of caloric intake and BMI, primarily because of the amount of activity rather than exercise intensity. Higher caloric intake further increases the risk of incident stones.

Demographics of pediatric renal trauma.

PURPOSE: There is a lack of national data describing the demographics and nature of pediatric renal trauma. We used the National Trauma Data Bank to analyze mechanisms and grades of injury, demographics and treatment characteristics of pediatric renal trauma cases. MATERIALS AND METHODS: Renal injuries were identified by Abbreviated Injury Scale codes and converted to American Association for the Surgery of Trauma renal injury grades. Patients were stratified by age (0 to 1, 2 to 4, 5 to 14 and 15 to 18 years) for more specific analyses of mechanisms and grades of injury. Data reviewed included mechanisms and grades of renal injury, demographics, and setting and type of treatment. RESULTS: A total of 2,213 pediatric renal injuries were converted to American Association for the Surgery of Trauma grade. Mean ± SD age at injury was 13.7 ± 4.4 years, with 2,089 patients (94%) being 5 to 18 years old. Of the injuries 79% were grade I, II or III. Penetrating injury accounted for less than 10% of all pediatric renal injuries. A majority of patients (57%) were admitted to university hospitals with a dedicated trauma service (73%) and only 12% of patients were admitted to a pediatric hospital. A total of 122 nephrectomies (5.5%) were performed. CONCLUSIONS: Most renal trauma in children is low grade, is blunt in nature and occurs after age 5 years. The majority of these cases are managed at adult hospitals. Although most patients are treated conservatively, the rate of nephrectomy is 3 times higher at adult hospitals than at pediatric centers.

Dietary intake of fiber, fruit and vegetables decreases the risk of incident kidney stones in women: a Women's Health Initiative report.

PURPOSE: We evaluated the relationship between dietary fiber, fruit and vegetable intake, and the risk of kidney stone formation. MATERIALS AND METHODS: Overall 83,922 postmenopausal women from the Women's Health Initiative observational study were included in the analysis and followed prospectively. Cox proportional hazards regression analyses were used to evaluate the associations between total dietary fiber, fruit and vegetable intake, and the risk of incident kidney stone formation, adjusting for nephrolithiasis risk factors (age, race/ethnicity, geographic region, diabetes mellitus, calcium supplementation, hormone therapy use, body mass index and calibrated caloric intake; and dietary water, sodium, animal protein and calcium intake). Women with a history of kidney stones (3,471) were analyzed separately. RESULTS: Mean age of the women was 64±7 years, 85% were white and 2,937 (3.5%) experienced a kidney stone in a median followup of 8 years. In women with no history of kidney stones higher total dietary fiber (6% to 26% decreased risk, p <0.001), greater fruit intake (12% to 25% decreased risk, p <0.001) and greater vegetable intake (9% to 22% decreased risk, p=0.002) were associated with a decreased risk of incident kidney stone formation in separate adjusted models. In women with a history of stones there were no significant protective effects of fiber, fruit or vegetable intake on the risk of kidney stone recurrence. CONCLUSIONS: Greater dietary intake of fiber, fruits and vegetables was associated with a reduced risk of incident kidney stones in postmenopausal women. The protective effects were independent of other known risk factors for kidney stones. In contrast, there was no reduction in risk in women with a history of stones.

Comparison of tissue injury from focused ultrasonic propulsion of kidney stones versus extracorporeal shock wave lithotripsy.

PURPOSE: Focused ultrasonic propulsion is a new noninvasive technique designed to move kidney stones and stone fragments out of the urinary collecting system. However, to our knowledge the extent of tissue injury associated with this technique is not known. We quantitated the amount of tissue injury produced by focused ultrasonic propulsion under simulated clinical treatment conditions and under conditions of higher power or continuous duty cycles. We compared those results to extracorporeal shock wave lithotripsy injury. MATERIALS AND METHODS: A human calcium oxalate monohydrate stone and/or nickel beads were implanted by ureteroscopy in 3 kidneys of live pigs weighing 45 to 55 kg and repositioned using focused ultrasonic propulsion. Additional pig kidneys were exposed to extracorporeal shock wave lithotripsy level pulse intensity or continuous ultrasound exposure 10 minutes in duration using an ultrasound probe transcutaneously or on the kidney. These kidneys were compared to 6 treated with an unmodified Dornier HM3 lithotripter (Dornier Medical Systems, Kennesaw, Georgia) using 2,400 shocks at 120 shock waves per minute and 24 kV. Histological analysis was performed to assess the volume of hemorrhagic tissue injury created by each technique according to the percent of functional renal volume. RESULTS: Extracorporeal shock wave lithotripsy produced a mean ± SEM lesion of 1.56% ± 0.45% of functional renal volume. Ultrasonic propulsion produced no detectable lesion with simulated clinical treatment. A lesion of 0.46% ± 0.37% or 1.15% ± 0.49% of functional renal volume was produced when excessive treatment parameters were used with the ultrasound probe placed on the kidney. CONCLUSIONS: Focused ultrasonic propulsion produced no detectable morphological injury to the renal parenchyma when using clinical treatment parameters but produced injury comparable in size to that of extracorporeal shock wave lithotripsy when using excessive treatment parameters.