Exploring optimal settings for safe and effective thulium fibre laser lithotripsy in a kidney model.

OBJECTIVES: To explore the optimal laser settings and treatment strategies for thulium fibre laser (TFL) lithotripsy, namely, those with the highest treatment efficiency, lowest thermal injury risk, and shortest procedure time. MATERIALS AND METHODS: An in vitro kidney model was used to assess the efficacy of TFL lithotripsy in the upper calyx. Stone ablation experiments were performed on BegoStone phantoms at different combinations of pulse energy (EP ) and frequency (F) to determine the optimal settings. Temperature changes and thermal injury risks were monitored using embedded thermocouples. Experiments were also performed on calcium oxalate monohydrate (COM) stones to validate the optimal settings. RESULTS: High EP /low F settings demonstrated superior treatment efficiency compared to low EP /high F settings using the same power. Specifically, 0.8 J/12 Hz was the optimal setting, resulting in a twofold increase in treatment efficiency, a 39% reduction in energy expenditure per unit of ablated stone mass, a 35% reduction in residual fragments, and a 36% reduction in total procedure time compared to the 0.2 J/50 Hz setting for COM stones. Thermal injury risk assessment indicated that 10 W power settings with high EP /low F combinations remained below the threshold for tissue injury, while higher power settings (>10 W) consistently exceeded the safety threshold. CONCLUSIONS: Our findings suggest that high EP /low F settings, such as 0.8 J/12 Hz, are optimal for TFL lithotripsy in the treatment of COM stones. These settings demonstrated significantly improved treatment efficiency with reduced residual fragments compared to conventional settings while keeping the thermal dose below the injury threshold. This study highlights the importance of using the high EP /low F combination with low power settings, which maximizes treatment efficiency and minimizes potential thermal injury. Further studies are warranted to determine the optimal settings for TFL for treating kidney stones with different compositions.

New devices for kidney stone management.

PURPOSE OF REVIEW: The purpose of this review is to summarize recent developments in the array of devices which are commonly used by urologists in the surgical management of kidney stones. To accomplish this goal, an extensive review of recent endourology literature, conference abstracts, and publicly available documents from manufacturers and the United States Food and Drug Administration was collected and reviewed. RECENT FINDINGS: Recent developments in the holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy include the introduction of pulse modulation. This technique delivers the laser energy in an asymmetric manner such that an initial bubble is created (the 'Moses effect') through which the remainder of the energy can then travel through without being absorbed by surrounding water. Even more novel is the thulium fiber laser, which is produced in a fundamentally different way than traditional Ho:YAG lasers and is not yet available for clinical use. Finally, novel mechanical lithotrites which effectively combine ultrasonic energy, ballistic energy, and suction capability appear to be highly effective for stone clearance in recent benchtop and clinical studies. SUMMARY: With the introduction of both new modifications of time-tested technologies as well as completely novel modalities, the practicing urologist's armamentarium of devices for the surgical management of kidney stones continues to grow. As the popularity of 'mini' procedures continues to grow, the adaptability of these technologies to these procedures will be critical to maintain maximum relevance.

Psychiatric Diagnoses and Other Factors Associated with Emergency Department Return within 30 Days of Ureteroscopy.

PURPOSE: Emergency department visits after ureteroscopy are costly and inconvenient. To better understand those at risk we aimed to identify patient demographic, medical and surgical factors associated with 30-day emergency department presentation following ureteroscopy for urolithiasis with particular attention to those with a history of a psychiatric diagnosis. MATERIALS AND METHODS: We retrospectively reviewed 1,576 cases (1,395 adults) who underwent stone related ureteroscopy during 3 years at a total of 2 hospitals. We collected patient demographics, medical history and operative details. The primary outcome was return to the emergency department within 30 days of ureteroscopy. Logistic regression was performed to examine factors associated with emergency department presentation. RESULTS: Of the patients 613 (43.9%) had a history of psychiatric diagnosis. Of those with ureteroscopy encounters 12.6% returned to the emergency department within 30 days of ureteroscopy, including 58.8% with a history of psychiatric diagnosis. On multivariable analysis variables associated with emergency department return included a history of psychiatric diagnosis (OR 1.57, p = 0.012), uninsured status (OR 2.46, p = 0.001) and a stone only in the kidney (OR 1.76, p = 0.022). Patients who returned to the emergency department had had more emergency department visits in the year prior to surgery (OR 1.40, p <0.001). On univariable analysis older patients and those with longer operative time were more frequently admitted from the emergency department (OR 1.03, p = 0.002 and OR 1.96, p = 0.03. respectively) while uninsured patients were admitted less frequently (OR 0.19, p = 0.013). No difference was noted in admissions between those with a psychiatric diagnosis and all others (60.7% vs 55.8%, p = 0.48). CONCLUSIONS: We identified factors associated with emergency department return after ureteroscopy, including a history of psychiatric diagnosis, uninsured status and emergency department visits in the year before surgery. These patients may benefit from targeted interventions to help avoid unnecessary emergency department visits.

Treatment Response in Patients with Stones, and Low Urinary pH and Hypocitraturia Stratified by Body Mass Index.

PURPOSE: Obesity has been shown to be a risk factor for kidney stone formation. Obesity leads to insulin resistance which subsequently leads to low urinary pH. Low urinary pH is typically treated with potassium citrate. We determined if the response to potassium citrate for the treatment of low urinary pH and hypocitraturia varied when patients were stratified by body mass index. MATERIALS AND METHODS: We retrospectively reviewed the records of patients with urolithiasis and concomitant hypocitraturia and low urinary pH as unique abnormalities upon metabolic evaluation treated exclusively with potassium citrate. Based on body mass index the cohort was divided into the 4 groups of normal weight, overweight, obese and morbidly obese. Metabolic data were compared among the 4 groups at baseline and subsequent followup visits up to 2 years. We compared urinary pH and citrate in absolute values and the relative changes in these parameters from baseline. Similarly, we compared the rates of potassium citrate treatment failure. RESULTS: A total of 125 patients with hypocitraturia and low urinary pH were included in this study. Median patient age was 61 years, 80 patients were male and median body mass index was 30.4 kg/m(2). Patients with a higher body mass index tended to be younger (p=0.010), and had a lower urinary citrate but higher sodium, oxalate and uric acid levels. Urinary pH was similar across body mass index groups. pH values and their absolute changes from baseline were lower as body mass index increased (p ≤0.001). Similarly, we noted an association between increasing body mass index category and lower urinary citrate levels accompanied by a statistically significant trend indicating lower absolute changes in citrate with increasing body mass index (p ≤0.001). Potassium citrate dose was increased more frequently among the higher body mass index groups. CONCLUSIONS: Patients with a higher body mass index presented with a lower increase in citrate excretion and urinary pH levels after they were started on potassium citrate, and they needed more frequent adjustments to their therapy.

Complications of surgical management of upper tract calculi in spina bifida patients: analysis of nationwide data.

PURPOSE: The management of upper urinary tract stones in patients with spina bifida is challenging but poorly described in the literature. We compared urolithiasis interventions and related complications in patients with spina bifida to those in other stone formers using a national database. MATERIALS AND METHODS: We retrospectively reviewed the NIS to identify hospital admissions for renal and ureteral stones from 1998 to 2011. We used ICD-9-CM codes to identify urological interventions, including shock wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy and ureteral stent placement. NSQIP data were used to identify postoperative complications. RESULTS: We identified 4,287,529 weighted stone hospital admissions, including 12,315 (0.3%) of patients with spina bifida. Compared to those without spina bifida the patients with spina bifida who had urolithiasis were significantly younger (mean age 34 vs 53 years), more likely to have public insurance (72% vs 44%) and renal vs ureteral calculi (81% vs 58%), and undergo percutaneous nephrolithotomy (27% vs 8%). After adjusting for age, insurance, comorbidity, treatment year, surgery type, stone location and hospital factors patients with spina bifida were more likely to have urinary tract infections (OR 2.5), urinary complications (OR 3.1), acute renal failure (OR 1.9), respiratory complications (OR 2.0), pneumonia (OR 1.5), respiratory insufficiency (OR 3.2), prolonged mechanical ventilation (OR 3.2), sepsis (OR 2.7), pulmonary embolism (OR 3.0), cardiac complications (OR 2.4) and bleeding (OR 1.6). CONCLUSIONS: Compared to those without spina bifida the patients with spina bifida who were hospitalized for urolithiasis were younger, and more likely to have renal stones and undergo percutaneous nephrolithotomy. Urolithiasis procedures in patients with spina bifida were associated with a significantly higher risk of in-hospital postoperative complications.

Estimating the nationwide, hospital based economic impact of pediatric urolithiasis.

PURPOSE: The incidence of urolithiasis is increasing in children and adolescents but the economic impact of this problem is unclear. We examined 2 large databases to estimate the nationwide economic impact of pediatric urolithiasis. MATERIALS AND METHODS: We analyzed the 2009 NEDS and KID, used ICD-9-CM codes to identify children 18 years or younger diagnosed with urolithiasis and abstracted demographic and charge data from each database. RESULTS: We identified 7,348 weighted inpatient discharges in KID and 33,038 emergency department weighted encounters in NEDS. Of the patients 32% and 36% were male, respectively. Inpatients were younger than those who presented to the ED (mean age 13.9 vs 15.7 years). Most patients had private insurance (52.9% to 57.2%) and the South was the most common geographic region (39.5% to 44.4%). The most common procedures were ureteral stent placement in 20.4% to 24.1% of cases, followed by ureteroscopy in 3.8% to 4.4%. Median charges per admission were $13,922 for a weighted total of $229 million per year. Median emergency department charges were $3,991 per encounter for a weighted total of $146 million per year. CONCLUSIONS: Each day in 2009 in the United States an estimated 20 children were hospitalized and 91 were treated in the emergency department for upper tract stones. A conservative estimate of 2009 annual charges related to pediatric urolithiasis in the United States is at least $375 million. This is likely a significant underestimate of the true economic burden of pediatric urolithiasis because it accounts for neither outpatient management nor indirect costs such as caregiver time away from work.

Radiation Exposure during the Evaluation and Management of Nephrolithiasis.

PURPOSE: There is rising concern over the increasing amount of patient radiation exposure from diagnostic imaging and medical procedures. Patients with nephrolithiasis are at potentially significant risk for radiation exposure due to the need for imaging to manage recurrent stone disease. We reviewed the literature in an attempt to better characterize actual risks and discussed methods to reduce radiation exposure for adult patients with nephrolithiasis. MATERIALS AND METHODS: A PubMed search was performed using the key words nephrolithiasis, stones, radiation, fluoroscopy, ureteroscopy, percutaneous nephrolithotomy, computerized tomography and shock wave lithotripsy. Additional citations were identified by reviewing reference lists of pertinent articles. RESULTS: A total of 50 relevant articles were included in this review. Patients with a first time acute stone event are exposed to a significant amount of radiation. Most radiation is from computerized tomography. Patients undergoing percutaneous nephrolithotomy are exposed to an equal or greater amount of radiation than they received from computerized tomography. Risk factors for increased exposure during percutaneous nephrolithotomy include obesity, multiple tracts and a larger stone burden. Ureteroscopy exposes patients to approximately the same amount of radiation as plain x-ray of the kidneys, ureters and bladder. Risk factors for increased exposure during ureteroscopy include obesity and ureteral dilation. During shock wave lithotripsy the amount of radiation exposure is not well characterized. Interventions to reduce exposure to patients include using ultrasound when possible and implementing low dose computerized tomography protocols. The as low as reasonably achievable principle of radiation exposure should always be followed when fluoroscopy is performed. The use of an air retrograde pyelogram may also reduce exposure during percutaneous nephrolithotomy. Fluoroscopy time during ureteroscopy may be decreased by a laser guided C-arm, a dedicated C-arm technician, stent placement under direct vision and tactile feedback to help guide wire placement. CONCLUSIONS: Patients with nephrolithiasis are at significant risk for increased radiation exposure from the imaging and fluoroscopy used during treatment. The true risks of low radiation exposure remain uncertain. It is important to be aware of these risks to provide better counseling for patients. Urologists must also be familiar with techniques to decrease radiation exposure for patients with nephrolithiasis.

Balloon Dilation of the Ureter: A Contemporary Review of Outcomes and Complications.

PURPOSE: During ureteroscopy ureteral balloon dilation may be necessary to allow for passage of endoscopic instruments or access sheaths. We assessed the efficacy and complications associated with ureteral balloon dilation. MATERIALS AND METHODS: We retrospectively reviewed the records at 2 institutions from 2000 to 2012 to identify patients who underwent ureteral balloon dilation during ureteroscopic treatment of upper tract stones. An 18Fr balloon dilator was used in all cases. Patients with documented ureteral stricture, radiation therapy or urothelial cancer were excluded from analysis. Primary outcomes were the stone-free rate, operative complications, balloon dilation failure and the postoperative ureteral stricture rate. Complications were divided into intraoperative and postoperative groups according to the Satava and Clavien-Dindo classifications, respectively. RESULTS: A total of 151 patients fulfilled study criteria. Median followup was 12 months. The stone-free rate was 72% and median time to first postoperative imaging was 2.8 months. Balloon dilation failed in only 8 patients (5%). Eight intraoperative ureteral perforations (5%) were identified, which were managed by a ureteral stent in 7 patients and a percutaneous tube in 1. Endoscopic re-treatment was required in 4 patients with Satava 2b postoperative complications. The postoperative complication rate was 8% (11 cases). A single ureteral stricture was attributable to balloon dilation. CONCLUSIONS: In this contemporary review balloon dilation of the ureter before endoscopic treatment of stone disease was associated with a high success rate and few complications. Ureteral balloon dilation may decrease the need for a secondary procedure in patients undergoing ureteroscopy to manage proximal ureteral and intrarenal stones.

A prospective, multi-institutional study of flexible ureteroscopy for proximal ureteral stones smaller than 2 cm.

PURPOSE: Flexible ureteroscopy is rapidly becoming a first line therapy for many patients with renal and ureteral stones. However, current understanding of treatment outcomes in patients with isolated proximal ureteral stones is limited. Therefore, we performed a prospective, multi-institutional study of ureteroscopic management of proximal ureteral stones smaller than 2 cm to better define clinical outcomes associated with this approach. MATERIALS AND METHODS: Adult patients with proximal ureteral calculi smaller than 2 cm were prospectively identified. Patients with concomitant ipsilateral renal calculi or prior ureteral stenting were excluded from study. Flexible ureteroscopy, holmium laser lithotripsy and ureteral stent placement was performed. Ureteral access sheath use, laser settings and other details of perioperative and postoperative management were based on individual surgeon preference. Stone clearance was determined by the results of renal ultrasound and plain x-ray of the kidneys, ureters and bladder 4 to 6 weeks postoperatively. RESULTS: Of 71 patients 44 (62%) were male and 27 (38%) were female. Mean age was 48.2 years. ASA(®) score was 1 in 12 cases (16%), 2 in 41 (58%), 3 in 16 (23%) and 4 in 2 (3%). Mean body mass index was 31.8 kg/m(2), mean stone size was 7.4 mm (range 5 to 15) and mean operative time was 60.3 minutes (range 15 to 148). Intraoperative complications occurred in 2 patients (2.8%), including mild ureteral trauma. Postoperative complications developed in 6 patients (8.7%), including urinary tract infection in 3, urinary retention in 2 and flash pulmonary edema in 1. The stone-free rate was 95% and for stones smaller than 1 cm it was 100%. CONCLUSIONS: Flexible ureteroscopy is associated with excellent clinical outcomes and acceptable morbidity when applied to patients with proximal ureteral stones smaller than 2 cm.

Disposable devices for RIRS: where do we stand in 2013? What do we need in the future?

PURPOSE: Disposable devices for retrograde intrarenal surgery (RIRS) form a significant part of the urologist's armamentarium for the endoscopic management of urologic diseases. Herein, we provide an overview of the literature regarding the advances and controversies of these devices. METHODS: A PubMed search was used to identify the literature discussing the subject of disposable devices for RIRS. Articles published between 2012 and 2013 were considered. RESULTS: Ureteral access implements including access sheaths, wires, and dilators are an area of both improvement and controversy regarding their proper use. The safety, effectiveness, and limitations of lithotrites continue to be refined. Stone retrieval devices are undergoing persistent miniaturization, and their use may prove to be cost effective. The debate over perioperative stenting remains, while symptom management is explored. A cost-effective option for disposable flexible ureteroscopy shows promise. CONCLUSIONS: While rapid advances in technology and knowledge continue, continual improvements are necessary. Disposable equipment needs persistent refinement and possible miniaturization. More efficient fragment retrieval devices are needed. Durability of laser fibers and safety within ureteroscopes needs to be improved. Reducing stent morbidity remains an ongoing challenge. Lastly, costs need to be reduced by the further development of disposable flexible ureteroscopes and in the recyclability of disposable devices to improve availability worldwide.

Shock wave lithotripsy: the new phoenix?

INTRODUCTION: Following its introduction in 1980, shock wave lithotripsy (SWL) rapidly emerged as the first-line treatment for the majority of patients with urolithiasis. Millions of SWL therapies have since been performed worldwide, and nowadays, SWL still remains to be the least invasive therapy modality for urinary stones. During the last three decades, SWL technology has advanced in terms of shock wave generation, focusing, patient coupling and stone localization. The implementation of multifunctional lithotripters has made SWL available to urology departments worldwide. Indications for SWL have evolved as well. Although endoscopic treatment techniques have improved significantly and seem to take the lead in stone therapy in the western countries due to high stone-free rates, SWL continues to be considered as the first-line therapy for the treatment of most intra-renal stones and many ureteral stones. METHODS: This paper reviews the fundamentals of SWL physics to facilitate a better understanding about how a lithotripter works and should be best utilized. RESULTS: Advances in lithotripsy technology such as shock wave generation and focusing, advances in stone localization (imaging), different energy source concepts and coupling modalities are presented. Furthermore adjuncts to improve the efficacy of SWL including different treatment strategies are reviewed. CONCLUSION: If urologists make use of a more comprehensive understanding of the pathophysiology and physics of shock waves, much better results could be achieved in the future. This may lead to a renaissance and encourage SWL as first-line therapy for urolithiasis in times of rapid progress in endoscopic treatment modalities.

Does body mass index impact the outcomes of tubeless percutaneous nephrolithotomy?

OBJECTIVE: To evaluate whether body mass index (BMI) has an impact on the outcomes of tubeless percutaneous nephrolithotomy (PCNL). PATIENTS AND METHODS: We retrospectively reviewed patients who underwent tubeless PCNL at our institution from 2006 to 2011. Specifically, stone-free rates, complications, and hospital length of stay (LOS) were assessed. Patients were divided into four groups based on BMI: <25, 25-29.9, 30-34.9 and ≥35 kg/m(2) . Baseline characteristics and outcomes were compared between BMI groups. Multivariable logistic regressions were used to evaluate the independent contribution of BMI as a predictor of outcomes. RESULTS: We identified 268 patients who fulfilled study requirements. The overall stone-free and complication rates were 52.5% and 19.0%, respectively. Minor and severe complication comprised 10.4% and 8.6%, respectively. Univariate and multivariable analyses showed no association between BMI and stone-free or complication rates. However, patients with a normal BMI had significantly higher transfusion rates (P = 0.005), and were significantly more likely to have a prolonged LOS (≥2 days), when compared with an overweight BMI (P = 0.032) CONCLUSIONS: BMI did not impact the stone-free, or complication rates of tubeless PCNL. Normal BMI was found to be a risk factor for prolonged LOS, which may be due to an increase in clinically significant bleeding in this patient population. Tubeless PCNL appears to be a safe and effective procedure for the treatment of complex renal calculi, independent of BMI.

Antiretropulsion devices.

PURPOSE OF REVIEW: Stone migration during the treatment of ureteral stones can prove frustrating and increases both healthcare cost and patient morbidity. Antiretropulsion devices have been engineered to prevent stone migration. RECENT FINDINGS: Improvements in antiretropulsion devices allow for efficient prevention of stone migration during ureteroscopic lithotripsy with minimal adverse effects or complications. Multiple devices are now available each with advantages and disadvantages. New devices are currently engineered to prevent stone migration and maintain ureteral access. Antiretropulsion devices appear to be cost-effective to prevent stone migration during intracorporeal lithotripsy. SUMMARY: Antiretropulsion devices have been safely and effectively used during ureteroscopic procedures. These tools increase stone-free rates, decrease morbidity and new studies have demonstrated their cost-effectiveness.

As low as reasonably achievable: Methods for reducing radiation exposure during the management of renal and ureteral stones.

Imaging for urolithiasis has evolved over the past 30 years. Currently, non-contrast computed tomography (NCCT) remains the first line imaging modality for the evaluation of patients with suspected urolithiasis. NCCT is a dominant source of ionizing radiation for patients and one of its major limitation. However, new low dose NCCT protocols may help to reduce the risk. Fluoroscopy use during operating room (OR) surgical procedures can be a substantial source of radiation for patients, OR staff and surgeons. It is important to consider the amount of radiation patients are exposed to from fluoroscopy during operative interventions for stones. Radiation reduction can be accomplished by appropriate selection of imaging studies and multiple techniques, which minimize the use of fluoroscopy whenever possible. The purpose of this manuscript is to review common imaging modalities used for diagnosing and management of renal and ureteral stones associated with radiation exposure. We also review alternatives and techniques to reduce radiation exposure.

Translating ethical and quality principles for the effective, safe and fair development, deployment and use of artificial intelligence technologies in healthcare.

OBJECTIVE: The complexity and rapid pace of development of algorithmic technologies pose challenges for their regulation and oversight in healthcare settings. We sought to improve our institution's approach to evaluation and governance of algorithmic technologies used in clinical care and operations by creating an Implementation Guide that standardizes evaluation criteria so that local oversight is performed in an objective fashion. MATERIALS AND METHODS: Building on a framework that applies key ethical and quality principles (clinical value and safety, fairness and equity, usability and adoption, transparency and accountability, and regulatory compliance), we created concrete guidelines for evaluating algorithmic technologies at our institution. RESULTS: An Implementation Guide articulates evaluation criteria used during review of algorithmic technologies and details what evidence supports the implementation of ethical and quality principles for trustworthy health AI. Application of the processes described in the Implementation Guide can lead to algorithms that are safer as well as more effective, fair, and equitable upon implementation, as illustrated through 4 examples of technologies at different phases of the algorithmic lifecycle that underwent evaluation at our academic medical center. DISCUSSION: By providing clear descriptions/definitions of evaluation criteria and embedding them within standardized processes, we streamlined oversight processes and educated communities using and developing algorithmic technologies within our institution. CONCLUSIONS: We developed a scalable, adaptable framework for translating principles into evaluation criteria and specific requirements that support trustworthy implementation of algorithmic technologies in patient care and healthcare operations.

Assessment of a modified acoustic lens for electromagnetic shock wave lithotripters in a swine model.

PURPOSE: The acoustic lens of the Modularis electromagnetic shock wave lithotripter (Siemens, Malvern, Pennsylvania) was modified to produce a pressure waveform and focal zone more closely resembling that of the original HM3 device (Dornier Medtech, Wessling, Germany). We assessed the newly designed acoustic lens in vivo in an animal model. MATERIALS AND METHODS: Stone fragmentation and tissue injury produced by the original and modified lenses of the Modularis lithotripter were evaluated in a swine model under equivalent acoustic pulse energy (about 45 mJ) at 1 Hz pulse repetition frequency. Stone fragmentation was determined by the weight percent of stone fragments less than 2 mm. To assess tissue injury, shock wave treated kidneys were perfused, dehydrated, cast in paraffin wax and sectioned. Digital images were captured every 120 µm and processed to determine functional renal volume damage. RESULTS: After 500 shocks, the mean ± SD stone fragmentation efficiency produced by the original and modified lenses was 48% ± 12% and 52% ± 17%, respectively (p = 0.60). However, after 2,000 shocks, the modified lens showed significantly improved stone fragmentation compared to the original lens (mean 86% ± 10% vs 72% ± 12%, p = 0.02). Tissue injury caused by the original and modified lenses was minimal at a mean of 0.57% ± 0.44% and 0.25% ± 0.25%, respectively (p = 0.27). CONCLUSIONS: With lens modification the Modularis lithotripter demonstrates significantly improved stone fragmentation with minimal tissue injury at a clinically relevant acoustic pulse energy. This new lens design could potentially be retrofitted to existing lithotripters, improving the effectiveness of electromagnetic lithotripters.

Obesity triples the radiation dose of stone protocol computerized tomography.

PURPOSE: Patients with recurrent nephrolithiasis are often evaluated and followed with computerized tomography. Obesity is a risk factor for nephrolithiasis. We evaluated the radiation dose of computerized tomography in obese and nonobese adults. MATERIALS AND METHODS: We scanned a validated, anthropomorphic male phantom according to our institutional renal stone evaluation protocol. The obese model consisted of the phantom wrapped in 2 Custom Fat Layers (CIRS, Norfolk, Virginia), which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the phantoms to measure organ specific radiation doses. The nonobese and obese models have an approximate body mass index of 24 and 30 kg/m(2), respectively. Three runs of renal stone protocol computerized tomography were performed on each phantom under automatic tube current modulation. Organ specific absorbed doses were measured and effective doses were calculated. RESULTS: The bone marrow of each model received the highest dose and the skin received the second highest dose. The mean ± SD effective dose for the nonobese and obese models was 3.04 ± 0.34 and 10.22 ± 0.50 mSv, respectively (p <0.0001). CONCLUSIONS: The effective dose of stone protocol computerized tomography in obese patients is more than threefold higher than the dose in nonobese patients using automatic tube current modulation. The implication of this finding extends beyond the urological stone population and adds to our understanding of radiation exposure from medical imaging.

The effect of dietary sodium and fructose intake on urine and serum parameters of stone formation in a pediatric mouse model: a pilot study.

PURPOSE: Dietary factors have a role in stone disease in adults but little is known about the relationship in children. We tested whether diet could alter urine and serum parameters in a pediatric mouse model. MATERIALS AND METHODS: We randomized 30 female BALB/c mice at age 3 weeks to mouse chow, a complex carbohydrate Western diet or a high fructose, high sodium Western diet. Body weight was measured twice weekly. Urine was periodically collected and mice were sacrificed on day 30. Samples were pooled to analyze serum and urine electrolyte factors. RESULTS: There was no significant difference in body weights among the groups at any time or in kidney weight at sacrifice (each p >0.15). There was no observable increase in urine stone forming analytes across the arms except uric acid, which tended to be higher in the Western diet and high fructose, high sodium Western diet groups. There was a substantial decrease in urinary stone inhibitors (magnesium and citrate), a decrease in urinary potassium and an increase in serum calcium in the 2 Western diet groups. CONCLUSIONS: This pilot study suggests that consuming a Western diet, especially one composed of high fructose and sodium, may alter parameters that predispose to stone formation in children by decreasing stone inhibitors. Results require validation in larger studies and ultimately in humans.

Radiation exposure in urology: a genitourinary catalogue for diagnostic imaging.

PURPOSE: Computerized tomography use increased exponentially in the last 3 decades, and it is commonly used to evaluate many urological conditions. Ionizing radiation exposure from medical imaging is linked to the risk of malignancy. We measured the organ and calculated effective doses of different studies to determine whether the dose-length product method is an accurate estimation of radiation exposure. MATERIALS AND METHODS: An anthropomorphic male phantom validated for human organ dosimetry measurements was used to determine radiation doses. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations to measure specific organ doses. For each study the phantom was scanned 3 times using our institutional protocols. Organ doses were measured and effective doses were calculated on dosimetry. Effective doses measured by a metal oxide semiconductor field effect transistor dosimeter were compared to calculated effective doses derived from the dose-length product. RESULTS: The mean±SD effective dose on dosimetry for stone protocol, chest and abdominopelvic computerized tomography, computerized tomography urogram and renal cell carcinoma protocol computerized tomography was 3.04±0.34, 4.34±0.27, 5.19±0.64, 9.73±0.71 and 11.42±0.24 mSv, respectively. The calculated effective dose for these studies Was 3.33, 2.92, 5.84, 9.64 and 10.06 mSv, respectively (p=0.8478). CONCLUSIONS: The effective dose varies considerable for different urological computerized tomography studies. Renal stone protocol computerized tomography shows the lowest dose, and computerized tomography urogram and the renal cell carcinoma protocol accumulate the highest effective doses. The calculated effective dose derived from the dose-length product is a reasonable estimate of patient radiation exposure.