Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

The purpose of this study was to measure and compare renal pelvic pressure (RPP) between prone and supine percutaneous nephrolithotomy (PCNL) in a benchtop model. Six identical silicone kidney models were placed into anatomically correct prone or supine torsos constructed from patient CT scans in the corresponding positions. A 30-Fr renal access sheath was placed in either the upper, middle, or lower pole calyx for both prone and supine positions. Two 9-mm BegoStones were placed in the respective calyx and RPPs were measured at baseline, irrigating with a rigid nephroscope, and irrigating with a flexible nephroscope. Five trials were conducted for each access in both prone and supine positions. The average baseline RPP in the prone position was significantly higher than the supine position (9.1 vs 2.7 mmHg; p < 0.001). Similarly, the average RPP in prone was significantly higher than supine when using both the rigid and flexible nephroscopes. When comparing RPPs for upper, middle, and lower pole access sites, there was no significant difference in pressures in either prone or supine positions (p > 0.05 for all). Overall, when combining all pressures at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position compared to the supine position (14.0 vs 3.2 mmHg; p < 0.001). RPPs were significantly higher in the prone position compared to the supine position in all conditions tested. These differences in RPPs between prone and supine PCNL could in part explain the different clinical outcomes, including postoperative fever and stone-free rates.

Not All Flat-Panel C-Arms Are Created Equal: A Comparison of Three Major Manufacturers

Introduction: Flat-panel detector C-arms (FCs) are reported to reduce radiation exposure and improve image quality compared with conventional image intensifier C-arms (CCs). The purpose of this study was to compare radiation exposure and image quality between three commonly used FCs. Materials and Methods: A cadaver model was placed in the prone position to simulate percutaneous nephrolithotomy. We compared the following three FCs: OEC Elite CFD from GE HealthCare, Zenition 70 from Philips, and Ziehm Vision RFD from Ziehm Imaging. To measure the radiation dose, optically stimulated luminescence dosimeters (OSLDs) were utilized during five 300-second trials, conducted under three settings: automatic exposure control (AEC), AEC with low dose (LD), and LD with the lowest pulse rate (LDLP). Ten blinded urologists evaluated the image quality. Data were statistically analyzed using the analysis of variance (ANOVA) and Tukey's B post hoc tests. Results: In the AEC setting, the Philips C-arm demonstrated lower ventral OSLD exposure (42,446 mrad) compared with both the GE (51,076 mrad) and Ziehm (83,178 mrad; p < 0.001) C-arms. Similarly, in the LD setting, the Philips C-arm resulted in less ventral OSLD exposure (25,926 mrad) than both the Ziehm (30,956 mrad) and GE (38,209 mrad; p < 0.001) C-arms. Meanwhile, in the LDLP setting, the Ziehm C-arm showed less ventral OSLD exposure (4019 mrad) than both the GE (7418 mrad) and Philips (8229 mrad; p < 0.001) C-arms. All three manufacturers received adequate image quality ratings at the AEC and LD settings. However, at LDLP, the Ziehm C-arm received inadequate ratings in 8% of images, whereas both the GE and Philips C-arms received 100% adequate ratings (p = 0.016). Conclusions: Radiation produced by flat-panel C-arms varies dramatically, with the highest exposure (Ziehm) being almost double the lowest (Philips) in AEC. Improved picture quality at the lowest settings may come at the cost of increased radiation dose. Surgeons should carefully select the machine and settings to minimize radiation exposure while still preserving the image quality.

Do Flat Panel Detector C-Arms Decrease Radiation Exposure Compared to Conventional Image Intensifiers?

OBJECTIVE

To compare the radiation dose and image quality between flat panel detector (FPD) and traditional image intensifier (II) C-arms at their lowest radiation settings.

METHODS

In a ureteroscopy simulation using a cadaver model, the radiation exposure was compared between FPD and II at 4 pulses-per-second (pps) using both low dose and automatic exposure control (AEC) settings. Additionally, the lowest dose settings for each machine were compared (4 pps with low dose in the FPD and 1 pps with low dose in the II). Five trials of 5 minutes were conducted for each setting. Four new optically stimulated luminescent dosimeters were used in each trial to record radiation exposure. Ten blinded urologists completed a survey rating image quality for each setting.

RESULTS

When comparing the FPD and II at their lowest possible settings, the FPD produced significantly more radiation (P <.05). Using both machines at 4 pps in low dose mode resulted in no significant difference between C-arms (P >.05). Conversely, operating the C-arms at 4 pps and AEC resulted in significantly higher radiation exposure from the FPD compared to the II (P <.05). There was no significant difference in image quality at each setting.

CONCLUSION

FPDs produce significantly more radiation at the lowest settings compared to IIs. Surgeons should employ IIs when reducing radiation exposure as low as possible is imperative, such as when operating on pediatric and pregnant patients.

Reducing hand radiation during renal access for percutaneous nephrolithotomy: a comparison of radiation reduction techniques

Percutaneous nephrolithotomy confers the highest radiation to the urologist's hands compared to other urologic procedures. This study compares radiation exposure to the surgeon's hand and patient's body when utilizing three different techniques for needle insertion during renal access. Simulated percutaneous renal access was performed using a cadaveric patient and separate cadaveric forearm representing the surgeon's hand. Three different needle-holding techniques were compared: conventional glove (control), a radiation-attenuating glove, and a novel needle holder. Five 300-s fluoroscopy trials were performed per treatment arm. The primary outcome was radiation dose (mSv) to the surgeon's hand. The secondary outcome was radiation dose to the patient. One-way ANOVA and Tukey's B post-hoc tests were performed with p < 0.05 considered significant. Compared to the control (3.92 mSv), both the radiation-attenuating glove (2.48 mSv) and the needle holder (1.37 mSv) reduced hand radiation exposure (p < 0.001). The needle holder reduced hand radiation compared to the radiation-attenuating glove (p < 0.001). The radiation-attenuating glove resulted in greater radiation produced by the C-arm compared to the needle holder (83.49 vs 69.22 mGy; p = 0.019). Patient radiation exposure was significantly higher with the radiation-attenuating glove compared to the needle holder (8.43 vs 7.03 mSv; p = 0.027). Though radiation-attenuating gloves decreased hand radiation dose by 37%, this came at the price of a 3% increase in patient exposure. In contrast, the needle holder reduced exposure to both the surgeon's hand by 65% and the patient by 14%. Thus, a well-designed low-density needle holder could optimize radiation safety for both surgeon and patient.

Time Efficiency and Performance of Single-Use vs Reusable Cystoscopes: A Randomized Benchtop and Simulated Clinical Assessment

Introduction: A flexible cystoscope is an indispensable tool for urologists, facilitating a variety of procedures in both the operating room and at bedside. Single-use cystoscopes offer benefits including accessibility and decreased burden for reprocessing. The aims of this study were to compare time efficiency and performance of single-use and reusable cystoscopes. Methods: Ten new Ambu® aScope™ 4 Cysto single-use and two Olympus CYF-5 reusable cystoscopes were compared in simulated bedside cystoscopy and benchtop testing. Ten urologists performed simulated cystoscopy using both cystoscopes in a randomized order. Times for supply-gathering, setup, cystoscopy, cleanup, and cumulative time were recorded, followed by a Likert feedback survey. For benchtop assessment, physical, optical, and functional specifications were assessed and compared between cystoscopes. Results: The single-use cystoscope demonstrated shorter supply-gathering, setup, cleanup, and cumulative times (824 vs 1231 seconds; p < 0.05) but a comparable cystoscopy time to the reusable cystoscope (202 vs 212 seconds; p = 0.32). The single-use cystoscope had a higher image resolution, but a narrower field of view. Upward deflection was greater for the single-use cystoscope (214.50° vs 199.45°; p < 0.01) but required greater force (2.5 × ). The working channel diameter and irrigation rate were greater in the reusable cystoscope. While the single-use cystoscope lacked tumor enhancing optical features, it had higher Likert scale scores for Time Efficiency and Overall Satisfaction. Conclusion: The single-use cystoscope demonstrates comparable benchtop performance and superior time efficiency compared to reusable cystoscopes. However, the reusable cystoscope has superior optical versatility and flow rate. Knowledge of these differences allows for optimal cystoscope selection based on procedure indication.

Which Laser System Is Optimal for Cystolithotripsy of Large Bladder Calculi?

Introduction and Objective: A variety of laser sources are available to treat bladder stones. The aim of this study was to compare time and cost efficiency of the thulium fiber laser (TFL) to four holmium lasers (HLs) with different powers or technologies, including MOSES™ during simulated cystolithotripsy. Materials and Methods: In a benchtop simulation of laser cystolithotripsy, 25 identical 4-cm BegoStones (calcium oxalate monohydrate consistency) were placed on a grid within a 3D-printed bladder model. Lasers were operated at maximal energy, using a 550 μm fiber. Lasers compared were as follows: 60 W TFL, 120 W HL with MOSES, and conventional 120, 100, and 30 W HLs. Five trials were performed for each laser with endpoints of laser time, total time, number of fiber strippings, and total energy. Cost-effectiveness was modeled using laser purchase price, fiber, and operating room (OR) time cost. ANOVA with Tukey's B post hoc was performed to compare outcomes. Spearman's test was used to assess correlation between laser power and procedure time. Results: The laser and total operating times were significantly different between the five systems (p < 0.001). The 120 W HL with MOSES was the fastest with 60.9 minutes of laser and 68.3 minutes of procedure times, while the 30 W HL was the slowest with 281.2 minutes of laser and 297.5 minutes of procedure times. The 60 W TFL was faster than the 30 W HL, but slower than the higher power HLs. Higher laser power was associated with shorter procedure time (Rs = -0.98; p = 0.002). When estimating cost per procedure, the MOSES HL was the cheapest, but had the highest purchase cost. The TFL was not cost-effective for large bladder stones compared with the 100 W HL. Conclusions: When treating large bladder stones, total laser power was highly correlated with laser and procedure times and the TFL was limited by its total power. The most cost-effective laser for use will depend on the case volume.

Liposomal versus plain bupivacaine for pain control following vaginal reconstruction

INTRODUCTION

Liposomal bupivacaine (LB) is a depot formulation of bupivacaine, which releases the drug over 72 hours to prolong local pain control. This retrospective study compares the effect of using LB versus plain bupivacaine on postoperative pain control, length of hospital stay and cost among patients undergoing vaginal reconstructive surgery.

MATERIALS AND METHODS

Patients who underwent vaginal reconstructive surgery with levatorplasty and received an injection of 20 cc of either plain bupivacaine or LB for pudendal nerve block were included. The primary outcomes included postoperative narcotic use and subjective pain score. The secondary outcome was postoperative length of stay. Comparisons between groups were performed using the T test, Mann Whitney U and Chi-square tests with p < 0.05 considered significant.

RESULTS

Between June 2016 and December 2021, 25 patients had received LB as a pudendal nerve block and 25 had received plain bupivacaine. Demographics between groups were similar. There was no difference between postoperative morphine equivalent dose (MED) for plain bupivacaine versus LB (25.3 ± 65.8 vs. 24.9 ± 31.7 MED; p = 0.159) or length of hospital stay (15.8 ± 12.0 hours vs. 23.8 ± 20.0; p = 0.094). Furthermore, subjective pain was also similar between groups (0 vs. 1.6 ± 2.6, p = 0.68), (4.6 ± 2.3 vs. 4.9 ± 2.0 average POD 1 pain, p = 0.534) and (4.3 ± 2.1 for vs. 4.9 ± 2.1 average POD 2 pain, p = 0.373).

CONCLUSION

LB is not superior to plain bupivacaine for controlling pain following vaginal reconstructive surgery, and justification for the exponentially greater cost of LB is not supported. Prospective investigations with larger sample sizes are needed to determine the optimal pain management for levatorplasty in vaginal reconstructive surgery.

Does renal failure worsen radiation cystitis following radical prostatectomy?

OBJECTIVE

To investigate the impact of renal function on the risk, severity, and management of radiation cystitis in patients who underwent postoperative radiation therapy for prostate cancer.

METHODS

Retrospective data was assessed from patients treated with adjuvant/salvage radiation therapy at a single academic institution between 2006 and 2020. The incidence, severity, and management of radiation cystitis were compared between three groups: CKD 0-2, CKD 3-4, and CKD 5. Associations of clinicopathologic factors with radiation cystitis were assessed in univariate and multivariate Cox regression models.

RESULTS

A total of 110 patients who underwent radiation therapy following robot-assisted laparoscopic radical prostatectomy were included. The incidence of radiation cystitis following postoperative radiation therapy was 17% with a median presentation time of 34 months (interquartile range 16-65 months). The incidence of radiation cystitis was 100% in CKD 5 patients compared to 15% in CKD 0-2 and 17% in CKD 3-4 patients (p < 0.001). CKD 5 patients required more treatments, emergency department visits, and longer hospitalization times than CKD 0-4 patients (all p < 0.001). Multivariate analyses identified CKD 5 as the only significant factor associated with radiation cystitis (HR = 10.39, p = 0.026).

CONCLUSION

End-stage renal failure is associated with the risk and severity of radiation cystitis in patients receiving postoperative radiation therapy. Knowledge of the potential morbidity of this complication in this population could guide physicians and patients as they evaluate risks and benefits prior to selecting adjuvant or salvage radiation therapy.

Thulium versus holmium for in situ lower pole laser lithotripsy

INTRODUCTION

During in situ lower pole laser lithotripsy, the dependent location may result in increased challenge fragmenting stones and a risk for stone regrowth if residual fragments remain. The purpose of this study was to compare the thulium fiber laser (TFL) with the holmium laser (HL) for in situ lower pole lithotripsy.

MATERIALS AND METHODS

In a 3D printed kidney benchtop model, sixty 1 cm BegoStones were placed in the lower pole and fragmented in situ until fragments passed through a 2 x 2 mm mesh. Laser lithotripsy was performed using twelve energy, frequency and fiber size combinations and residual fragments were compared. In addition, laser fiber diameters and subsequent ureteroscope deflections and flow rates were compared between fibers.

RESULTS

The TFL resulted in decreased residual fragments compared to the HL (11% vs. 17%, p < 0.001) and the three settings with least residual fragments were all TFL. Compared to the 150 µm TFL (265° deflection), there was a loss of 9° and 34° in the 200 µm TFL and 272 µm HL fibers, respectively. The measured fiber sizes were greater than manufacturer specified fiber size in every instance. Irrigation rates inversely correlated with fiber size.

CONCLUSION

The TFL resulted in 35% less residual stone fragments, up to 34° additional deflection, and an increased irrigation rate when compared to the HL. Optimal fragmentation settings are identified to further improve lower pole lithotripsy. The combination of reduced residual fragments, improved deflection, and better flow rates make the TFL advantageous for in situ lower pole lithotripsy.

Does the Novel Thulium Fiber Laser Have a Higher Risk of Urothelial Thermal Injury than the Conventional Holmium Laser in an In Vitro Study?

INTRODUCTION AND OBJECTIVE

The novel thulium fiber laser (TFL) has been shown to break stones more rapidly than the holmium:YAG laser (HL). However, some evidence suggests that the TFL generates more heat. The purpose of this study is to compare ureteral temperatures generated by these lasers during ureteroscopic laser lithotripsy in a benchtop model.

METHODS

A 1-cm BegoStone was manually impacted in the proximal ureter of a 3D printed kidney-ureter model and submerged in 35.5°C saline. Lithotripsy was performed using a 7.6 French flexible ureteroscope and a 200µm laser fiber without a ureteral access sheath. The Dornier 30W HL, Olympus 100W HL, and Olympus 60W TFL were compared. A needle thermocouple to measure temperature was inserted 2 mm from the laser tip. Irrigation was maintained at 35cc/min at room temperature using the Thermedx FluidSmart System. Intraluminal temperature was continuously recorded for 60 seconds of laser activation. 5 trials were performed for each of 4 different power settings: 3.6, 10, 20, and 30 Watts. ANOVA and Mann-Whitney U tests were performed with p<0.05 considered significant.

RESULTS

Intraureteral fluid temperature increased as laser power settings increased for all lasers (p<0.05). The TFL generated higher average ureteral fluid temperatures than the Dornier and Empower HL at all power settings tested (p<0.001). The maximum temperature for the TFL was higher than the Dornier and Empower HL at all power settings tested (p<0.001), except at 20W with the Empower HL. At 30W, the TFL exceeded 43°C, the threshold for tissue damage.

CONCLUSIONS

The TFL generated more heat at all settings tested. Supraphysiologic ureteral temperatures may be generated with extended use at high energy settings and low irrigation rates. Understanding the heat generation properties of both lasers could help improve the safety of ureteroscopic laser lithotripsy.

Does qSOFA score predict ICU admission and outcomes in patients with obstructed infected ureteral stones?

INTRODUCTION

Obstructing stones with infection represent a true urologic emergency requiring prompt decompression. Historically the systemic inflammatory response syndrome (SIRS) criteria has been used to predict outcomes in patients with sepsis. The quick Sequential Organ Failure Assessment (qSOFA) score has been proposed as a prognostic factor in patients with acute pyelononephritis associated with nephrolithiasis. However there has been limited application of qSOFA to patients undergoing ureteral stenting with obstructive pyelonephritis. The purpose of this study was to evaluate the predictive value of the qSOFA score for postoperative outcomes following renal decompression in this patient population.

MATERIALS AND METHODS

A retrospective review was conducted at three medical centers within one academic institution to identify patients with obstructive pyelonephritis secondary to ureteral stones. All patients underwent emergent ureteral stent placement for decompression. The primary outcome was the predictive value of preoperative qSOFA score ≥ 2 for intensive care unit (ICU) admission postoperatively. Univariate analysis and multivariate regression analysis were performed to identify factors associated with postoperative outcomes, with p < 0.05 considered significant.

RESULTS

Of the 289 patients who had ureteral stents placed, 147 patients met inclusion criteria. Twenty-four (16.3%) patients required ICU admission and there were 3 (2%) mortalities, all of these within the ICU admission group. The sensitivity and specificity of the qSOFA score ≥ 2 for ICU admission was 70.8% and 79.5% respectively which outperformed SIRS criteria, which had a sensitivity and specificity of 100% and 33.6% respectively.

CONCLUSION

A preoperative qSOFA score ≥ 2 was a significant predictor for postoperative ICU admission in patients undergoing ureteral stent placement for obstructive pyelonephritis. The qSOFA score can be used to determine which patients will require ICU admission.

Reduced radiation fluoroscopy technique for implantation of sacral neuromodulation

Introduction:

Sacral neuromodulation (SNM) is a Food and Drug Administration–approved treatment option for urinary urgency and fecal incontinence. Fluoroscopic imaging is used at various steps during lead placement, which exposes the operating room staff and patient to the harmful effects of radiation. The aim of this study is to describe a reduced radiation technique during lead placement for treatment with SNM.

Methods:

A retrospective cohort of 51 consecutive patients who underwent lead insertion and SNM placement at a single academic institution were investigated. Reduced fluoroscopy (RF; n=11) involved C-arm settings to 1 pulse/second and an activated “low-dose” setting, while conventional fluoroscopy (CF; n=40) involved 30 pulses/second and a deactivated “low-dose” setting. The automatic brightness control and collimation were used optionally in both groups. Comparison of imaging quality, fluoroscopy settings, and radiation exposure during RF and CF was performed.

Results:

RF settings resulted in significant reduction of radiation compared to CF settings, including the fluoroscopy time (8.61 vs. 48.16 seconds; p<0.001), dose (2.66 vs. 26.25 mGy; p=0.001), and current (1.67 vs. 4.18 mAs; p<0.001). There was no significant difference in total operative time (59.18 vs. 61.33 minutes; p=0.77) and the rate of progression from stage 1 to stage 2 during follow-up (75% vs. 84%; p=0.55).

Conclusions:

Lead placement for treatment with SNM can be achieved using RF settings without compromising clinical outcomes. Applying the RF technique reduces overall radiation exposure to the patient and the operating room staff. Further validation of RF in a larger prospective cohort study is needed.

Level of evidence:

Level 4.

Guidewire type and prior use affects ureteral stent insertion force

INTRODUCTION

To improve the success rate and safety of ureteral stent insertion, we sought to identify the effect of guidewire type and prior use upon the force needed to advance a 6Fr ureteral stent over various guidewires.

MATERIALS AND METHODS

Two-hundred forty stent insertion trials were performed in an ex vivo porcine urinary tract model. Ten trials were randomly performed over 12 new and 12 used guidewires. For each trial, the force required to advance a 6Fr Cook double-pigtail ureteral stent was recorded. Guidewires included the Olympus Glidewire, Cook Fixed Core, and Boston Scientific Amplatz Super Stiff, Sensor, ZIPwire, and Zebra wire.

RESULTS

The mean force needed for stent advancement was the lowest for the new Glidewire (0.18N) and ZIPwire (0.22N), with no significant difference to each other (p = 0.90). The following new wires required increasingly higher stent insertion forces compared to the Glidewire, the Zebra (0.60N; p < 0.01), Fixed Core (1.25N; p < 0.01), Sensor (1.43N; p < 0.01), and Amplatz Super Stiff wires (2.03N; p < 0.01). There was no statistical difference between new and used Glidewires (0.18N versus 0.29N; p = 0.14) and Zebra wires (0.59N versus 0.60N; p = 0.88). All other used wires required a significantly greater advancement force than their new counterparts (p < 0.01).

CONCLUSIONS

For the same stent, the force required for stent advancement varies greatly between guidewire types. In addition, used guidewires typically required more force compared to new guidewires. In long or difficult cases, switching to a new wire may improve the ease of stent placement and reduce potential complications.

The Effect of Lemonade and Diet Lemonade Upon Urinary Parameters Affecting Calcium Urinary Stone Formation

PURPOSE

To determine the effects of regular and diet lemonade upon urinary parameters affecting kidney stone formation.

METHODS

In this prospective blinded crossover study, 12 healthy participants consumed either 2 L of regular or diet lemonade daily while on a standardized low sodium moderate calcium diet. Twenty four-hour urine collections were obtained at baseline on the controlled diet only and on days 4 and 5 of each treatment phase. There was a 1-week washout period between regular and diet lemonade treatments. Primary outcomes were urine citrate, pH, and volume determined by 24-hour urine collections. Secondary outcomes included the supersaturation of calcium oxalate, calcium phosphate, and uric acid.

RESULTS

Urine volume was significantly higher with both regular and diet lemonade consumption compared with baseline values. Urinary citrate significantly increased from baseline with diet lemonade only. Urine pH was unchanged with both beverages. The supersaturation of calcium oxalate significantly decreased with diet lemonade only, whereas supersaturation of calcium phosphate decreased with both beverages. Daily consumption of 2 L of regular and diet lemonade resulted in an intake of 168.4 and 170.2 mEq of citrate but a total alkali intake of 12.2 and 16.0 mEq, respectively. Compared with diet lemonade, regular lemonade provided subjects with 805 additional calories and 225 g of sugar per day.

CONCLUSIONS

Diet lemonade may provide a low-calorie sugar-free cost-effective option for decreasing the risk of recurrent calcium nephrolithiasis through a significant increase in urine volume, increase in urinary citrate, and reduction in supersaturation of calcium oxalate and calcium phosphate.

The Impact of Patient, Procedural, and Staffing Factors Upon Ureteroscopy Cost

Introduction: The purpose of this study was to evaluate factors during ureteroscopy that can potentially impact procedure cost. Materials and Methods: A retrospective review of 129 consecutive elective ureteroscopy cases was performed to determine direct procedure cost. Direct cost was defined as cost incurred because of operating room expenses, including operating room time, staffing expenses, equipment, and supply costs. Data regarding patient, procedural, and operating room staffing characteristics were compared between the most and least expensive cases. Univariate and logistic regression analysis were performed to identify factors predictive of higher costs. Results: The average direct ureteroscopy cost was $3298/case. On univariate analysis, ureteroscopies in the highest 50th cost percentile had larger stone burden (170.1 vs 146 mm²; p = 0.03) and longer operative times (95.3 vs 49.9 minutes; p < 0.01), were more likely performed for non-stone indications (21.4% vs 7.2%; p = 0.03), more likely to include a resident (65.5% vs 43.6%; p = 0.02), and less likely to have a dedicated urology scrub technician (38.2% vs 61.8%; p = 0.01) compared to cases in the lowest 50th percentile. The presence of a resident, larger stone burden, absence of a dedicated scrub technician, and longer operative time were associated with an average cost increase of $516, $700, $1122, and $1401, respectively. Logistic regression analysis showed that operating room time was the only factor predicting higher cost (OR [odds ratio] 12.8, 95% confidence interval [CI] 2.0-84.0). A post-hoc logistic regression analysis demonstrated that the presence of a resident during ureteroscopy (OR 2.9, 95% CI 1.1-8.0) and larger stone burden (OR 1.01, 95% CI 1.0-1.013) were significantly associated with longer operative times. Conclusion: Operating room time is the primary determinant of ureteroscopy case cost. All efforts should be made to decrease operative time, although balancing patient safety and maintaining a quality training environment.

What Guidewire Is the Best for Bypassing an Impacted Ureteral Stone?

Introduction and Objectives: To determine the optimal guidewire for bypassing an impacted ureteral stone. Materials and Methods: Three different benchtop models of varying impaction (300, 362, and 444 mm Hg pressure) were used to compare the ability of 13 different guidewires to bypass an impacted ureteral stone. In the first and second models, we recorded the maximum force required to bypass the stone. In the first model (300 mm Hg) 10 new wires for each of the 13 types were advanced past a ureteral stone using a series 5 digital force gauge. In the second model (362 mm Hg), the top 5 performing guidewires were similarly tested. In the third model (444 mm Hg), 5 attending urologists and 5 urology residents (blinded to wire type) compared the 13 guidewires and rated the wire performance using a Likert scale. Statistical analysis was performed with analysis of variance and the chi-square test. Results: In the first model, there was a significant difference between wires (p < 0.001) with the lowest mean force to bypass a stone seen in the Glidewire (0.117 ± 0.02 lbs) and HiWire (0.130 ± 0.01 lbs). Of the five wires tested in the second model, the Glidewire (0.24 ± 0.09 lbs) and UltraTrack (0.40 ± 0.35 lbs) both required less force than the other three wires (p = 0.018). In the third model, only two wires (Roadrunner and Glidewire) bypassed the impacted stone in 100% of trials. When comparing standard, hybrid, and hydrophilic wires, the hydrophilic had the highest success rate (standard = 0%, hybrid = 36.67%, and hydrophilic = 70.67%; p = 0.000) and Likert score (standard = 1.03, hybrid = 2.38, and hydrophilic = 3.24; p = 0.000). Hydrophilic wires required the least time to bypass the stone (hybrid = 82.81 seconds vs hydrophilic = 45.37 seconds, p = 0.000). Conclusions: In this benchtop study, standard wires performed poorly and hybrid wires were not as effective as hydrophilic wires. The Glidewire required the least force, the shortest insertion time, and had the highest surgeon satisfaction rating.

The Effect of Operative Field Instrument Clutter During Intraoperative Fluoroscopy on Radiation Exposure

Introduction and Objectives: Fluoroscopy units are routinely operated in the automatic brightness control (ABC) mode to optimize image quality. During ureteroscopy, objects may be placed within the fluoroscopy beam and the effect upon radiation exposure is unknown. The purpose of this study is to investigate the effects of equipment within the fluoroscopy beam during simulated ureteroscopy. Methods: ABC fluoroscopy of a cadaver was performed in eight clinical scenarios, including a control (no equipment), and seven groups with different equipment within the fluoroscopy beam. Equipment tested included electrocardiogram (EKG) leads, a Kelly clamp, camera and light cords (straight and coiled configurations), flexible ureteroscope, rigid cystoscope, and the lateral table support beam. Ten 145-second fluoroscopy trials were performed for each arm. The primary outcome was radiation dose (mGy) compared using the Mann-Whitney test with p < 0.05 considered significant. Results: Compared with control (18.5 mGy), radiation exposure was significantly increased with the presence of a straight camera and light cords (19.3 mGy), Kelly clamp (19.4 mGy), coiled camera and light cords (20.2 mGy), a flexible ureteroscope (21.0 mGy), a rigid cystoscope (21.2 mGy), and when the lateral table support beam was in the path of the X-ray (25.0 mGy; a 35% increase; p < 0.007 for all). The EKG leads did not affect the radiation dose. Conclusions: Avoiding equipment within the fluoroscopy beam using ABC mode can reduce radiation exposure. Adjusting the table and patient position to exclude the lateral table support beam will reduce radiation exposure by 35%.

How a Donor Nephrectomy Population Can Help Give Perspective to the Effects of Renal Parenchymal Preservation During Partial Nephrectomy

Introduction: Volume of renal parenchymal loss is known to affect postoperative renal function after partial nephrectomy (PN). We utilize a novel comparison using donor nephrectomy (DN) patients to demonstrate the primary effect parenchymal volume loss plays on postoperative renal function following PN. Materials and Methods: Records of 250 living donor (DN) and 118 PN patients were retrospectively reviewed. Baseline characteristics and preoperative estimated glomerular filtration rate (eGFR)s were recorded. Percent changes in eGFR and incidences of surgically induced chronic kidney disease (CKD-S) in short, intermediate, and long-term postoperative periods were compared. Univariate and multivariate analyses of prognostic factors for development of CKD-S were performed. The PN group was further divided into subgroups with different lengths of warm ischemia time (WIT) and compared with DN patients. Results: At baseline, DN patients were younger, less likely to be male, had lower body mass index, lower American Society of Anesthesiologists, and higher preoperative eGFR (all p < 0.001). At hospital discharge, intermediate follow-up, and latest follow-up, renal function changes in DN and PN groups were -40.5% vs. -3.6%, -34.1% vs. -5.5%, and -33.2% vs. -4.4%, respectively (all p < 0.001). More DN than PN patients developed CKD-S (p < 0.001). DN was a significant risk factor for the development of chronic kidney disease on univariate and multivariate analyses (p < 0.001). On subgroup analysis, both subgroups with WIT 1 to 30 minutes and 31 to 60 minutes had less renal function decline at all time points compared with DN (p < 0.001). Conclusions: Volume of renal parenchyma retained is the dominant driver of postoperative renal function after nephrectomy, compared with all other factors. Surgeons should minimize parenchymal loss during PN to optimize postoperative renal function.

A realistic, durable, and low-cost training model for percutaneous renal access using ballistic gelatin

OBJECTIVE

The purpose of this study was to design and implement a realistic, durable, and low-cost training model for percutaneous renal access.

MATERIAL AND METHODS

Ballistic gelatin mixed with radiographic contrast was poured into surgical gloves to create a radio-dense renal collecting system. The collecting system model was then embedded in a pure ballistic gelatin block resting upon a clear acrylic glass base. Finally, the model was covered by a visually opaque polyurethane foam cover with chalk sticks positioned to simulate ribs. Experienced attending urologists and interventional radiologists, urology residents, and medical students used the model to access the upper, middle, and lower renal calyces under fluoroscopic guidance. Outcomes included model durability, realism rated by participants on a visual analogue scale, and cost.

RESULTS

The ballistic gelatin model was durable and anatomically realistic. Each model sustained over 200 needle punctures with no significant compromise in structural integrity or any contrast leakage. Attending and resident physicians considered it to provide an accurate simulation of renal access and medical students and residents considered the model to be a practical training modality (residents 8.4/10 vs. medical students 9.4/10). The total cost for one model was $60.

CONCLUSION

The ballistic gelatin collecting system provided a realistic, durable, and low-cost renal access training model. This could allow trainees to develop skills without compromising patient safety.

Impact of a Wireless System Upon Verbal Communication in a Simulated Robotic Operating Theater

OBJECTIVE

To compare the efficacy of communication via the standard Da Vinci Si speaker system with a wireless, hands-free audio system in a prospective blinded study.

METHODS

Nine hundred and sixty surgical phrases were spoken in a simulated robotic operating room (OR), including 480 phrases expressed via the Da Vinci Si speakers and 480 phrases expressed through a wireless, hands-free system. Using a dual console robotic system, communication was evaluated. Wireless headsets were given to the console and assistant robotic console surgeons, bedside assistant, anesthesiologist, and circulating nurse. An accurate response was defined as hearing the phrase correctly and transcribing it on a data sheet. The primary outcome was the number of correct phrases recorded during the study and secondary outcomes included subjective clarity and effectiveness of communication reported using a Likert scale.

RESULTS

Overall, the wireless, hands-free system increased the accuracy of communication (390/480 [81.3%]) compared to the conventional robotic system (310/480 [64.4%]; P <.001). The bedside assistant, anesthesiologist, and circulating nurse had significantly fewer correct phrases recorded than the assistant robotic console surgeon when using the robotic speakers (P <.05 for all). In contrast, there were no significant differences in the number of correct phrases recorded between different positions when using the wireless system. Subjectively, the wireless system resulted in improved clarity and effectiveness of communication (P = .021; P <.001, respectively).

CONCLUSION

Robotic operating systems have intrinsic barriers to effective communication between the surgeon and the rest of the operating room team. Improved communication could reduce surgical errors and improve patient safety.

Should donors who have used marijuana be considered candidates for living kidney donation?

Background

The use of marijuana in the USA has been steadily increasing over the last 10 years. This study is the first to investigate the effect of marijuana use by live kidney donors upon outcomes in both donors and recipients.

Methods

Living kidney donor transplants performed between January 2000 and May 2016 in a single academic institution were retrospectively reviewed. Donor and recipient groups were each divided into two groups by donor marijuana usage. Outcomes in donor and recipient groups were compared using t-test, Chi-square and mixed linear analysis (P < 0.05 considered significant).

Results

This was 294 living renal donor medical records were reviewed including 31 marijuana-using donors (MUD) and 263 non-MUDs (NMUD). It was 230 living kidney recipient records were reviewed including 27 marijuana kidney recipients (MKRs) and 203 non-MKRs (NMKR). There was no difference in donor or recipient perioperative characteristics or postoperative outcomes based upon donor marijuana use (P > 0.05 for all comparisons). There was no difference in renal function between NMUD and MUD groups and no long-term difference in kidney allograft function between NMKR and MKR groups.

Conclusions

Considering individuals with a history of marijuana use for living kidney donation could increase the donor pool and yield acceptable outcomes.

Do Illuminated Foot Pedals Improve the Speed and Accuracy of Pedal Activation During Endoscopic Procedures?

PURPOSE

Endourologic procedures such as percutaneous nephrolithotomy (PCNL) employ the use of foot pedals in low-light operating room (OR) settings. These pedals can be especially difficult to locate or distinguish when several pedals are present during a single operation. Improper instrument activation in the OR has led to serious complications ranging from unintentional electrocautery to patient burns and even an intraoperative explosion. This study evaluates the impact of color-coded illumination on speed and efficiency of foot pedal activation.

MATERIALS AND METHODS

During a simulated PCNL procedure, the foot pedals for a C-arm, laser, and ultrasonic lithotripter (USL) were placed in random positions. Ten participants performed pedal activation in a randomized sequence. Objective outcomes included time to instrument activation, number of attempted pedal presses, number of incomplete pedal presses, and number of incorrect pedal presses. Subjective preferences for pedal illumination were also determined. Data were analyzed using Mann-Whitney U, Wilcoxon signed-rank, and Chi-square tests with p < 0.05 indicating statistical significance.

RESULTS

Illuminated foot pedals were associated with decreases in the average activation time for all instruments collectively (3.95 seconds vs 6.49 seconds; p = 0.017) and individually (C-arm: 3.07 seconds vs 4.21 seconds; p = 0.006; laser: 13.04 seconds vs 15.18 seconds; p < 0.001; USL: 3.28 seconds vs 4.91 seconds; p < 0.001) compared with nonilluminated pedals. Illuminated pedals were associated with fewer attempted pedal presses (33.5 vs 39.5; p = 0.007) and incomplete pedal presses (1.5 vs 8.5; p = 0.002). The number of incorrect pedal presses decreased with illumination, but this did not reach statistical significance (0 vs 0.5; p = 0.08). Participants reported that illumination simplified pedal activation and recommended its use (p < 0.01).

CONCLUSION

Color-coded illumination improved the speed and efficiency of foot pedal activation during simulated PCNL. Participants subjectively preferred using illuminated foot pedals for endourologic procedures and felt that they improved safety and efficiency.

Efficacy of antegrade and retrograde warm saline pyeloperfusion during renal cryoablation for ureteral preservation

Objective

Cryoablation of renal tumors adjacent to the ureter or pelvicalyceal system carries risks for thermal injury of the collecting system. Although cold antegrade perfusion has been described for radiofrequency ablation, warm saline perfusion for renal cryoablation has not been well-characterized. The purpose of this study was to determine the safety and feasibility of antegrade and retrograde warm saline perfusions during percutaneous renal cryoablation.

Material and methods

A retrospective review was performed on 136 patients treated with percutaneous renal cryoablation at a single academic institution between 2009 and 2015. Six patients undergoing antegrade (n=3) or retrograde (n=3) warm saline perfusion for protection of the collecting system were identified. Warm saline was perfused through a 4 French nephrostomy tube in the antegrade technique and through a 6 French end-hole catheter in the retrograde technique. Outcome measures were tumor recurrence rates, success of urothelial preservation, hospital stay, blood loss and procedural time.

Results

Four tumors were in the lower pole and two tumors in the middle pole. The mean distance from tumor to ureter was 6.8 mm (0.8-11.5 mm) and no patient developed ureteral stricture. There was no tumor recurrence at a median follow-up of 37.3 months (7-65). The median procedural time was 3 hours and 13 minutes. One patient in each group developed minor complications (Clavien I and II) and there were no major complications.

Conclusion

This study demonstrates the feasibility of antegrade and retrograde warm saline perfusion for ureteral preservation during cryoablation, without compromising oncologic outcomes.

Renal Pelvic Pressure in Percutaneous Nephrolithotomy: The Effect of Multiple Tracts

INTRODUCTION

During percutaneous nephrolithotomy (PCNL), elevated renal pelvic pressures (RPPs) may spread infection through pyelovenous backflow whereas decreased pressures can hinder observation and increase bleeding. The purpose of this study was to evaluate the effects of multiple access tracts and different sized endoscopic equipment on RPP in a porcine model.

MATERIALS AND METHODS

RPP was measured in one- vs two-tract access, rigid vs flexible nephroscopy, and suction vs no suction. Twenty trials were performed for each condition. An independent samples Mann-Whitney U-test was used to compare parameters, with p < 0.05 considered significant.

RESULTS

With one tract, rigid nephroscopy resulted in higher mean pressures (31.35 mm Hg) than flexible nephroscopy (11.1 mm Hg; p < 0.001). The RPP was higher with rigid nephroscopy in one tract (31.35 mm Hg) than when two tracts were present (9.35 mm Hg; p < 0.001). In contrast, there was no difference in pressure during the use of a flexible nephroscope in one (11.1 mm Hg) vs two tracts (10.7 mm Hg; p = 0.63). Use of suction with the rigid nephroscope resulted in significantly lower pressures with one (-1.3 mm Hg) than with two tracts (1.8 mm Hg; p = 0.004).

CONCLUSION

In PCNL, RPP is significantly affected by an additional tract during rigid nephroscopy and suctioning but not when using a flexible nephroscope. Understanding the effects of multiple tracts and equipment type on RPP may improve the safety of PCNL.

Jackets Off: The Impact of Laser Fiber Stripping on Power Output and Stone Degradation

PURPOSE

To investigate the effect of laser fiber stripping on stone fragmentation and laser fiber power output.

MATERIALS AND METHODS

In a benchtop simulation of laser lithotripsy, 20 BegoStone phantoms were positioned within a ureteral model and irradiated for 10 minutes at 8 Hz and 0.8 J. A freshly cleaved 365 μm laser fiber was used for all trials, with half of the fibers also undergoing stripping. Power output was measured at 1-minute intervals, beginning with an initial prelithotripsy recording at 0 minutes. Fiber tips were imaged with scanning electron microscopy. In a single-blinded manner, final masses of residual stone fragments were measured and used to quantify stone breakdown. Independent-sample Mann-Whitney U tests were performed with significance set at p < 0.05, comparing stripped and unstripped fiber tips with respect to power output and fraction of stone fragmentation.

RESULTS

Mean power output after 1 minute of lasing was significantly greater in unstripped laser fibers (p = 0.015), while fibers, whether stripped or not, demonstrated no significant output differences prelithotripsy or at any time from 2 to 10 minutes. However, stripped laser fibers achieved significantly increased stone breakdown compared to unstripped fibers (p = 0.004), fragmenting 63 mg (25%) more of the initial stone mass per trial.

CONCLUSIONS

Although unstripped laser fibers provided superior power output at 1 minute, output at all other time points was similar between stripped and unstripped fibers. However, despite similar optical output, stripped laser fibers achieved greater stone fragmentation, possibly due to improved contact between stone and fiber tip.

Profile of metabolic and infectious stone-formers in a contemporary PCNL cohort

INTRODUCTION

To identify factors associated with stone composition in patients undergoing percutaneous nephrolithotomy (PCNL).

MATERIAL AND METHODS

A retrospective analysis of patients who underwent PCNL at two academic institutions between 2002 and 2014. Stone composition, stone characteristics based on non-contrast computer tomography (NCCT), patient demographics, and the S.T.O.N.E nephrolithometry scores were compared. Stones were characterized as either infection or metabolic. Metabolic stones were classified as calcium phosphate-containing and all others.

RESULTS

A total of 192 renal units underwent PCNL. Retrieved stones were found to be 75% (144) metabolic and 25% (48) infection by stone analysis. Of the metabolic stones, 51% (73) were phosphate-containing calculi. Overall, infection stones were found to have a significantly higher S.T.O.N.E nephrolithometry score than metabolic stones (9.2 versus 8.1, p < 0.001). Average Hounsfield units (HU) were significantly lower in infection stones (765 versus 899, p < 0.05). Sixty-three percent of patients with infection stones were female as compared to 46% of patients with metabolic stones. Patients with phosphate-containing stones in the metabolic group were significantly more likely to be female (56% versus 35%, p < 0.01), younger (mean 49 versus 60 years of age, p < 0.02), and have lower BMI's (30 versus 32, p < 0.02) compared with other metabolic stones.

CONCLUSIONS

Patient demographics including age, sex and BMI differ between patients with phosphate and non-phosphate containing metabolic stones. Higher S.T.O.N.E nephrolithometry scores were found in infection stones. These findings may serve as useful tools in the identification of stone compositions that are being seen more frequently in large and complicated stones undergoing PCNL.

Predictors of narcotic use after percutaneous nephrolithotomy

INTRODUCTION

Percutaneous nephrolithotomy (PCNL) is associated with significant variability in postoperative pain and subsequent narcotic use. The purpose of this study was to determine the factors associated with high narcotic use following PCNL.

MATERIALS AND METHODS

A single-center retrospective review of patients undergoing initial PCNL between 2004 and 2014 was performed. Preoperative, intraoperative and postoperative factors associated with postoperative narcotic usage were analyzed. The primary outcome variable was mean narcotic usage, standardized to intravenous morphine-equivalents. Patients in the lowest 75th percentile were compared to those in the highest 25th percentile. Univariate and multivariate statistical analyses were performed, with p < 0.05 considered significant.

RESULTS

When the 243 patients were compared from lowest to highest quartile, total narcotic use during the first 48 hour period was 2.3, 8.4, 15.6, and 41.7 mg of morphine-equivalents. On univariate analysis, predictors of high narcotic use included age 20-39 (p < 0.001), preoperative narcotic use (p < 0.001), presence of a postoperative complication (p = 0.044), and high stone burden (p = 0.002). Age < 20 (p < 0.001) and > 60 years (p = 0.014) were associated with low narcotic use. On multivariate analysis, age 20-39 (OR 6.87, 95% CI 2.22-21.23, p = 0.001), male gender (OR 2.47, CI 1.05-5.81, p = 0.037), and preoperative narcotic use (OR 3.27, CI 1.41-7.60, p = 0.006) were associated with higher opioid requirement.

CONCLUSION

Patients who were aged 20-39, males, and those with prior narcotic exposure used the highest doses of narcotics postoperatively. Knowledge of the factors predictive of high narcotic usage may allow better preoperative management of patient expectations and more effective postoperative care to prevent the complications of high narcotic usage.

Percutaneous Externally Assembled Laparoscopic vs Laparoendoscopic Single-Site Nephrectomy in a Porcine Model: A Prospective, Randomized, Blinded, Study

OBJECTIVE

To compare the outcomes between laparoendoscopic single-site (LESS) and a novel percutaneous externally assembled laparoscopic (PEAL) nephrectomy in an in vivo porcine model.

MATERIALS AND METHODS

Ten female farm pigs were randomized to LESS nephrectomy (5) or PEAL nephrectomy (5). Operative times, estimated blood loss, and intraoperative and postoperative complications were compared. The surgeons used a Likert scale to grade difficulty of peritoneal access, port placement, tool assembly, hilar dissection, closure, and overall difficulty of surgery. Scar assessment was performed by a blinded plastic surgeon using the Vancouver Scar Scale. Descriptive statistics were reported as median and range. The Mann-Whitney U test was used for continuous and ordinal variables. A p value <0.05 was considered significant.

RESULTS

Median operative time was significantly shorter in the PEAL group vs the LESS group (85 minutes vs 127 minutes, p = 0.03). Median Likert scores showed overall hilar dissection and nephrectomy to be significantly easier using PEAL compared with LESS (2 vs 9, p < 0.01 for both). The PEAL instruments left no visible scar at 5 feet in any animal, and only 1 out of 10 scars could be identified on physical examination.

CONCLUSIONS

The PEAL surgical paradigm demonstrates nearly scarless outcomes while providing shorter operative times and easier performance than LESS nephrectomy in a porcine model.