Daniel A. Wollin

Variable Pulse Duration From a New Holmium:YAG Laser: The Effect on Stone Comminution, Fiber Tip Degradation, and Retropulsion in a Dusting Model

OBJECTIVEnTo more clearly define the efficiency and potential benefits of variable pulse-width laser technology for ureteroscopic lithotripsy, we performed comparative in vitro evaluations assessing stone comminution, laser fiber tip degradation, and stone retropulsion.nnnMETHODSnAll experiments were conducted using a Swiss LaserClast Holmium:YAG laser (Electro Medical Systems, Nyon, Switzerland) with adjustable pulse duration (300u2009µs-1500u2009µs). To assess comminution efficiency and fiber tip degradation, a dusting model was employed; the laser fiber tip was moved by a 3-dimensional positioning system in a spiral motion across a flat BegoStone surface submerged in water. Comminution efficiency was measured as the loss of stone mass while fiber tip degradation was measured simultaneously. The same laser and fiber were used in a pendulum model to measure stone retropulsion with a high-speed resolution camera.nnnRESULTSnIn our dusting model, comminution was significantly greater at high energy (2u2009J/5u2009Hz). At the high energy setting, comminution was significantly greater with long pulse duration than short pulse, although this difference was not seen at the high frequency setting (1u2009J/10u2009Hz). Tip degradation was increased at high energy settings and was even more pronounced with short pulse duration than long pulse. Short pulse duration caused far more retropulsion than the long pulse setting.nnnCONCLUSIONnIn an in vitro dusting model, a longer laser pulse duration provides effective stone comminution with the advantage of reducing laser fiber tip degradation and stone retropulsion.

Antibiotic use and the prevention and management of infectious complications in stone disease

The importance of assessing perioperative urine/stone cultures and providing appropriate antibiotic prophylaxis prior to shock wave lithotripsy (SWL) or endoscopic intervention cannot be minimized. Urinary tract infection (UTI) is the most common complication relating to stone intervention. Adequate assessment of culture data and adherence to appropriate guidelines may prevent the development of UTI and the potential for post-intervention urosepsis. This review outlines the current evidence for prophylaxis in the prevention of UTI and urosepsis, as well as the interpretation of stone culture data to provide an evidence-based approach for the judicious use of antibiotics in urologic stone practice.

Obesity and metabolic stone disease

Purpose of review In this article, we aim to review the data regarding associations between obesity and nephrolithiasis to assist with workup and treatment of these intersecting disorders. As obesity has a multifactorial influence on the risk for urinary stone disease, the complicated mechanisms will be discussed to improve diagnosis and management. Recent findings Obesity and metabolic syndrome interact with nephrolithiasis risk factors to produce a myriad of bodily responses that induce stone formation. For this reason, many societies recommend prompt metabolic workup to evaluate the precise causes of stone formation. Data have shown that dietary and directed medical therapies can produce an excellent therapeutic response in this patient population, although the response may be blunted compared with nonobese patients. Summary Given the increasing number of obese and overweight patients, the urologist should be familiar with the pathophysiology, workup, and treatment of metabolic stone disease in this population, which are outlined here.

Percutaneous nephrolithotomy: complications and how to deal with them

Percutaneous nephrolithotomy is a common surgical treatment for large and complex stones within the intrarenal collecting system. A wide variety of complications can result from this procedure, including bleeding, injury to surrounding structures, infection, positioning-related injuries, thromboembolic disease, and even death. Knowledge of the different types of complications can be useful in order to prevent, diagnose, and treat these problems if they occur. This review describes the diversity of complications with the goal of improving their avoidance and treatment.

Defining metabolic activity of nephrolithiasis – Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3–6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1–2 years.

PD35-05 HOW DO YOU LIKE YOUR POPCORN? AN EVALUATION OF LASER SETTINGS AND LOCATION IN THE EFFICIENCY OF THE POPCORN EFFECT

INTRODUCTION AND OBJECTIVES: There are many techniques for laser lithotripsy of urinary stones. The “popcorn” method involves placing a laser fiber in the center of a collection of stones and firing continuously, allowing fragments to further dust into smaller particles. Our aim was to examine different locations and laser settings on the efficiency of this lithotripsy method. METHODS: Pre-fragmented BegoStone phantoms were created between 2-4mm in size to mimic typical popcorning conditions. A 0.5g collection of fragments was placed into two 3D-printed models (a 2 cm spherical calyx model and 4x2 cm ellipsoid pelvis model, Figure 1) and a 200mm laser fiber was positioned at the top of the stones. The laser was fired for 2 minutes with constant irrigation, with 5 trials performed at each setting: 0.2J/50Hz, 0.5J/20Hz, 0.5J/40Hz, 1J/20Hz. The fragmentation efficiency was determined by calculating the mass of stones reduced to sub-2mm particles after 48h of drying. Statistical analysis was performed with ANOVA and Student’s T-test. Additionally, high-speed photography was used to examine the mechanism of the popcorn effect. RESULTS: The trials within the calyx model were significantly more efficient compared to the pelvis model (0.18g vs 0.13g, p<0.05). When comparing laser settings, there was a difference between groups by one-way ANOVA (F[3,36] 1⁄4 7.92, p 1⁄4 0.0003). Post hoc tests showed that 20W settings were significantly more efficient than 0.2J/ 50Hz (p<0.05) although 0.5J/20Hz was not significantly less efficient than the 20W settings (Figure 2). High-speed imaging shows the majority of fragmentation is due to intermittent stone contact with the laser as opposed to stone-stone interaction. CONCLUSIONS: The popcorn effect is most efficient in a smaller space as in the calyx model and as such we recommend displacement of stones into a calyx for popcorning. The 0.5J/20Hz setting produces efficient popcorning at a lower power of 10W, reducing fiber burnback and potential for injury, and is our recommended setting. Source of Funding: None

Abdominal Radiography With Digital Tomosynthesis: An Alternative to Computed Tomography for Identification of Urinary Calculi?

OBJECTIVEnTo compare the accuracy of plain abdominal radiography (kidneys, ureter, and bladder [KUB]) with digital tomosynthesis (DT) to noncontrast computed tomography (NCCT), the gold standard imaging modality for urinary stones. Due to radiation and cost concerns, KUB is often used for diagnosis and follow-up of nephrolithiasis. DT, a novel technique that produces high-quality radiographs with less radiation and/or cost than low-dose NCCT, has not been assessed in this situation.nnnMATERIALS AND METHODSnSeven fresh tissue cadavers were implanted with stones of known size and/or composition and imaged with KUB, DT, and NCCT. Four blinded readers (2 urologists, 2 radiologists) evaluated KUBs for presence and/or location of calculi. They then re-evaluated with addition of tomograms to assess additional value. After a memory extinction period, readers evaluated NCCT images. Accuracy of detection was determined using nearest-neighbor match with generalized linear mixed modeling.nnnRESULTSnTotal of 59 stones were identified on reference read. Overall, NCCT and DT were both superior to KUB alone (P < .001) while the difference between DT and NCCT was not significant (P = .06). When evaluating uric acid stones, NCCT and DT outperformed KUB (P < .01 and P < .05, respectively) while DT and NCCT were similar (Pu202f=u202f.16). Intrarenal stones were better evaluated on DT and NCCT (P < .001 compared to KUB), while DT and NCCT were similar (Pu202f=u202f1.00). Accuracy was lower than anticipated across modalities due to use of the cadaver model.nnnCONCLUSIONnOur study demonstrates DT is superior to KUB for identification of intrarenal calculi and could replace routine use of KUB or NCCT for detecting renal stones, even those composed of uric acid.

An in vitro evaluation of laser settings and location in the efficiency of the popcorn effect

To examine different locations and laser settings’ effects on the efficiency of the “popcorn” method of laser lithotripsy, which consists of placing the laser in a group of small stones and firing continuously to break them into smaller particles. Pre-fragmented BegoStones were created between 2 and 4xa0mm to mimic typical popcorning conditions. A 0.5xa0g collection of fragments was placed into 3D-printed models (a spherical calyx and ellipsoid pelvis model) and a 200-µm laser fiber was positioned above the stones. The laser was fired for 2xa0min with irrigation, with 5 trials at each setting: 0.2xa0J/50xa0Hz, 0.5xa0J/20xa0Hz, 0.5xa0J/40xa0Hz, 1xa0J/20xa0Hz, 0.2xa0J/80xa0Hz, 0.5xa0J/80xa0Hz. After drying, fragmentation efficiency was determined by calculating the mass of stones reduced to sub-2xa0mm particles. Statistical analysis was performed with ANOVA and Student’s t test. The trials within the calyx model were significantly more efficient compared to the pelvis (0.19 vs 0.15xa0g, pu2009=u20090.01). When comparing laser settings, there was a difference between groups by one-way ANOVA [F(5,54)u2009=u20098.503, pu2009=u20095.47u2009×u200910−6]. Post hoc tests showed a power setting of 0.5xa0J/80xa0Hz was significantly more efficient than low-power settings 0.2xa0J/50xa0Hz and 0.5xa0J/20xa0Hz (pu2009<u20090.05). Additionally, 0.2xa0J/50xa0Hz was significantly less efficient than 0.5xa0J/40xa0Hz, 1xa0J/20xa0Hz, and 0.2xa0J/80xa0Hz. Popcorning is most efficient in smaller spaces; we recommend displacement of stones into a calyx before popcorning. No difference was seen between high-power settings, although 0.5xa0J/40xa0Hz and 0.5xa0J/80xa0Hz performed best, suggesting that moderate energy popcorning methods with at least 0.5xa0J per pulse are most efficient.

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.

In Vitro Comparison of a Novel Single Probe Dual-Energy Lithotripter to Current Devices

PURPOSEnThe LithoClast Trilogy is a novel single probe, dual-energy lithotripter with ultrasonic (US) vibration and electromagnetic impact forces. ShockPulse and LithoClast Select are existing lithotripters that also use a combination of US and mechanical impact energies. We compared the efficacy and tip motion of these devices in an in vitro setting.nnnMATERIALS AND METHODSnBegostones, in the ratio 15:3, were used in all trials. Test groups were Trilogy, ShockPulse, Select ultrasound (US) only, and Select ultrasound with pneumatic (USP). For clearance testing, a single investigator facile with each lithotripter fragmented 10 stones per device. For drill testing, a hands-free apparatus with a submerged balance was used to apply 1 or 2u2009lbs of pressure on a stone in contact with the device tip. High-speed photography was used to assess Trilogy and ShockPulses probe tip motion.nnnRESULTSnSelect-USP was slowest and Trilogy fastest on clearance testing (pu2009<u20090.01). On 1u2009lbs drill testing, Select-US was slowest (pu2009=u20090.001). At 2u2009lbs, ShockPulse was faster than Select US (pu2009=u20090.027), but did not significantly outpace Trilogy nor Select-USP. At either weight, there was no significant difference between Trilogy and ShockPulse. During its US function, Trilogys maximum downward tip displacement was 0.041u2009mm relative to 0.0025u2009mm with ShockPulse. Trilogy had 0.25u2009mm of maximum downward displacement during its impactor function while ShockPulse had 0.01u2009mm.nnnCONCLUSIONSnSingle probe dual-energy devices, such as Trilogy and ShockPulse, represent the next generation of lithotripters. Trilogy more efficiently cleared stone than currently available devices, which could be explained by its larger probe diameter and greater downward tip displacement during both US and impactor functions.