Prone split-leg endoscopic-guided percutaneous nephrolithotomy: the surgeons perspective with A Gopro® view

ABSTRACT Introduction: To demonstrate the entire surgeon's point of view of a prone split-leg (PSL) endoscopic guided percutaneous nephrolithotomy (ePCNL) recorded with a GoPro® camera for standardization of the essential technical steps towards a successful procedure (1). Materials and methods: A 40y.o female patient presented with right flank pain for three years. She had previously been submitted to shock wave lithotripsy without success. Non-contrast computed tomography (NCCT) revealed a 2cm stone in the renal pelvis with 1400HU and stone-to-skin distance of 11cm (Guy's Stone Score 1). PCNL approach was chosen for providing higher chances of stone-free after a single procedure. Informed consent was obtained. The PSL ePCNL was uneventful with a single access in a mid-pole. The surgeon had a Full HD GoPro Hero 4® camera mounted on his head, controlled by the surgical staff with a remote control. All essential surgical steps were recorded. Results: Operative time was 90 minutes. Hemoglobin drop was 0.7g/dL. The post-operative NCCT scan was stone-free. The patient was discharged 24h after surgery. Kidney stent was left with a string and removed after 5days. The camera worked properly and didn't cause any kind of discomfort to the surgeon. The quality of the recorded movie was excellent. Conclusion: By recording the surgeon's perspective of an endoscopic urological procedure, we were able to provide a comprehensive understanding of the surgical technique by assembling the endoscopic, fluoroscopic, and operative field views. The GoPro® camera proved to be an interesting tool to document surgical procedures without compromising outcomes and has great potential for educational purposes.

High pressure endoscopic irrigation: impact on renal histology

ABSTRACT Purpose: High intra-renal pressures during flexible ureteroscopy have been associated with adverse renal tissue changes as well as pyelovenous backflow. Our objective was to investigate the effect of various intra-renal pressures on histologic changes and fluid extravasation during simulated ureteroscopy. Materials and Methods: Twenty-four juvenile pig kidneys with intact ureters were cannulated with an Olympus flexible ureteroscope with and without a ureteral access sheath and subjected to India ink-infused saline irrigation for 30 minutes at constant pressures ranging from sphygmomanometer settings of 50mm, 100mm and 200mmHg. Renal tissue samples were collected, processed and stained, and were evaluated by a blinded pathologist for depth of ink penetration into renal parenchyma as a percentage of total parenchymal thickness from urothelium to renal capsule. Results: The mean percentage of tissue penetration for kidneys with ink present in the cortical tubules at sphygmomanometer pressure settings of 50, 100, and 200mm Hg without a ureteral access sheath was 33.1, 31.0 and 99.3%, respectively and with ureteral access sheath was 0, 0 and 18.8%, respectively. Overall, kidneys with an access sheath demonstrated a smaller mean tissue penetration among all pressure compared to kidneys without a sheath (6.3% vs. 54.5%, p=0.0354). Of kidneys with sheath placement, 11% demonstrated any ink compared to 56% of kidneys without sheath placement. Conclusions: Pressurized endoscopic irrigation leads to significant extravasation of fluid into the renal parenchyma. Higher intra-renal pressures were associated with increased penetration of irrigant during ureteroscopy in an ex-vivo porcine model.

Staghorn renal stones: what the urologist needs to know

ABSTRACT Patients with staghorn renal stones are challenging cases, requiring careful preoperative evaluation and close follow-up to avoid stone recurrence. In this article we aim to discuss the main topics related to staghorn renal stones with focus on surgical approach. Most of staghorn renal stones are composed of struvite (magnesium ammonium phosphate) and are linked to urinary tract infection by urease-producing pathogens. Preoperative computed tomography scan and careful evaluation of all urine cultures made prior surgery are essential for a well-planning surgical approach and a right antibiotics choice. Gold standard surgical technique is the percutaneous nephrolithotomy (PCNL). In cases of impossible percutaneous renal access, anatrophic nephrolithotomy is an alternative. Shockwave lithotripsy and flexible ureteroscopy are useful tools to treat residual fragments that can be left after treatment of complete staghorn renal stone. PCNL can be performed in supine or prone position according to surgeon's experience. Tranexamic acid can be used to avoid bleeding. To check postoperative stone-free status, computed tomography is the most accurate imaging exam, but ultrasound combined to KUB is an option. Intra-operative high-resolution fluoroscopy and flexible nephroscopy have been described as an alternative for looking at residual fragments and save radiation exposure. The main goals of treatment are stone-free status, infection eradication, and recurrence prevention. Long-term or short-term antibiotic therapy is recommended and regular control imaging exams and urine culture should be done.

A comprehensive literature-based equation to compare cost-effectiveness of a flexible ureteroscopy program with single-use versus reusable devices

ABSTRACT Purpose to critically review all literature concerning the cost-effectiveness of flexible ureteroscopy comparing single-use with reusable scopes. Materials and Methods A systematic online literature review was performed in PubMed, Embase and Google Scholar databases. All factors potentially affecting surgical costs or clinical outcomes were considered. Prospective assessments, case control and case series studies were included. Results 741 studies were found. Of those, 18 were duplicated and 77 were not related to urology procedures. Of the remaining 646 studies, 59 were considered of relevance and selected for further analysis. Stone free and complication rates were similar between single-use and reusable scopes. Operative time was in average 20% shorter with digital scopes, single-use or not. Reusable digital scopes seem to last longer than optic ones, though scope longevity is very variable worldwide. New scopes usually last four times more than refurbished ones and single-use ureterorenoscopes have good resilience throughout long cases. Longer scope longevity is achieved with Cidex and if a dedicated nurse takes care of the sterilization process. The main surgical factors that negatively impact device longevity are lower pole pathologies, large stone burden and non-use of a ureteral access sheath. We have built a comprehensive financial cost-effective decision model to flexible ureteroscope acquisition. Conclusions The cost-effectiveness of a flexible ureteroscopy program is dependent of several aspects. We have developed a equation to allow a literature-based and adaptable decision model to every interested stakeholder. Disposable devices are already a reality and will progressively become the standard as manufacturing price falls.

Seasonal variations in urinary calcium, volume, and vitamin D in kidney stone formers

ABSTRACT Objectives: To investigate the seasonal variations in urinary calcium, serum vitamin D, and urinary volume in patients with a history of nephrolithiasis. Materials and Methods: Patients included were those who completed a 24-hour urine metabolic evaluation on two occasions; one in summer (June-Aug) and one in winter (Nov-Jan), and who had not started any medications or been instructed on dietary modifications in the interval between the two tests that may have impacted the results. Patients were excluded if they were on thiazide diuretics or were taking calcium and / or Vitamin D supplementation. Welch's t-test was used to compare the difference in average summer and winter values. Unpaired Student t-test was used to compare baseline parameters (age, BMI), and Paired Student t-test was used to compare average seasonal measurements in men vs. women. Results: 136 patients were identified who were not taking calcium or vitamin D supplements or thiazide diuretics, and who were not instructed on dietary modifications in the interval between the two measured parameters. No significant differences were observed when comparing male to female baseline parameters of age or BMI (Table-1). Average 24-hour urine calcium was higher (226.60) in the winter than in summer (194.18) and was significant in males (p = 0.014) and females (p < 0.001). No significant seasonal difference was seen in 24-hour urine volume or serum vitamin D levels. Conclusions: Urinary calcium is higher in winter months compared to summer months. As such, tailoring medical preventative strategies to the time of year may be helpful.

Ureteral access sheaths: a comprehensive comparison of physical and mechanical properties

ABSTRACT Introduction: Ureteral access sheaths (UAS) facilitate flexible ureteroscopy in the treat- ment of urolithiasis. The physical properties of UAS vary by manufacturer and model. We compared three new UAS: Glideway (GW, Terumo, 11/13Fr, 12/14Fr), Pathway (PW, Terumo 12/14F) and Navigator HD (NHD, Boston Scientific, 11/13Fr, 12/14Fr) in the domains of safety characteristics, positioning characteristics, lubricity and radio- opacity. Materials and Methods: In vitro testing of the three UAS included safety testing-tip perforation force, sheath edge deformation and dilator extraction forces. Positioning characteristics tested included tip bending, stiffness (resistance to coaxial buckling forces), kinking (resistance to perpendicular forces), and insertion forces. Lubricity was assessed by measured frictional forces of the outer sheath. Finally, radio-opacity was tested utilizing fluoroscopic imaging of the three 12F sheaths and inner dilators. Results: The PW (0.245 lb) and GW (0.286 lb) required less force for tip perforation compared to the NHD (0.628 lb). The NHD sheath edge deformation was mild compared to more severe deformation for the PW and GW. The PW (1.008 lb) required greater force than the GW (0.136 lb) and NHD (0.043 lb) for inner dilator removal. The GW (3.69 lbs) and NHD (4.17 lb) had similar inner dilator tip stiffness when bent, while the PW had the weakest inner dilator tip, 1.91 lbs. The PW (0.271 lb) was most susceptible to buckling and kinking (1.626 lb). The most lubricious UAS was the NHD (0.055 lbs for 12F). The NHD (0.277 lbs) required the least insertional force through a biological model and possessed the greatest radio-opacity. Conclusions: Comparison of different commercially available UAS in various sizes reveals that there are mechanical differences in sheaths that may play a role clinically. The Terumo sheaths' (GW and PW) were outperformed by the Boston Scientific NHD in simulating safety, ease of use and radio-opacity.

Quality of life and urolithiasis: the patient - reported outcomes measurement information system (PROMIS)

ABSTRACT Background: With a high rate of recurrence, urolithiasis is a chronic disease that impacts quality of life. The Patient Reported Outcomes Measurement Information System is an NIH validated questionnaire to assess patient quality of life. We evaluated the impact of urolithiasis on quality of life using the NIH-sponsored PROMIS-43 questionnaire. Materials and Methods: Patients reporting to the kidney stone clinic were interviewed to collect information on stone history and demographic information and were asked to complete the PROMIS-43 questionnaire. Quality of life scores were analyzed using gender and age matched groups for the general US population. Statistical comparisons were made based on demographic information and patient stone history. Statistical significance was P<0.05. Results: 103 patients completed the survey. 36% of respondents were male, the average age of the group was 52 years old, with 58% primary income earners, and 35% primary caregivers. 7% had never passed a stone or had a procedure while 17% passed 10 or more stones in their lifetime. Overall, pain and physical function were worse in patients with urolithiasis. Primary income earners had better quality of life while primary caregivers and those with other chronic medical conditions were worse. Patients on dietary and medical therapy had better quality of life scores. Conclusions: Urolithiasis patients subjectively have worse pain and physical function than the general population. The impact of pain on quality of life was greatest in those patients who had more stone episodes, underscoring the importance of preventive measures. Stone prevention measures improve quality of life.

Current practice of antibiotic utilization for renal colic in the emergency room

ABSTRACT Introduction Urinalysis (UA) in the emergency setting for patients with nephrolithiasis produces potentially confusing results leading to treatment of presumed urinary tract infections (UTIs). Our objective was to evaluate the use of antibiotics in patients with nephrolithiasis in a large network of emergency departments (EDs). Methods A retrospective analysis of all ED visits associated with an ICD-9 diagnosis of nephrolithiasis and a CT scan between 2010 and 2013 was performed. Urinalysis data, the use of IV and PO antibiotics during the ED visit and at discharge were assessed. The presence of fever, elevated serum WBCs, >5 WBCs per hpf, and/or dip positive nitrites were used as appropriate criteria for antibiotic use. Results Urinalysis data were available for 3,518 (70%) of 5,035 patients with an ED diagnosis of nephrolithiasis and CT imaging. Of these visits, 237 patients had positive nitrites (6.7%) and 864 had >5 WBCs per hpf (24.6%) with 158 (4.5%) having both findings for a total of 943 patients. Intravenous antibiotics were given to 244 patients (25.9%) and oral antibiotics were given to 629 patients (66.7 %) with positive UA findings. Of the 2,440 patients with a negative UA and no leukocytosis or fever, 86 patients (3.5%) received IV antibiotics and 533 patients (21.8%) received PO antibiotics upon discharge. Conclusions Proper treatment of nephrolithiasis in the ED includes the screening and diagnosis of concomitant UTIs. However, correct interpretation of UA studies is vital to the correct implementation of antibiotic therapy. This study suggests that 1/3 of patients were undertreated and 21.8% were over-treated.

Predicting procedural pain after ureteroscopy: does hydrodistention play a role?

ABSTRACT Purpose: To identify perioperative predictors of immediate pain after ureteroscopy, specifically evaluating the impact of hydrodistention from irrigation on pain. Materials and Methods: We retrospectively identified patients who underwent ureteroscopy for the treatment of calculi. Data recorded for these patients included their maximum pain score in the post-anesthesia care unit (PACU), average flow rate of irrigant used during the procedure, patient and stone characteristics, operative procedure, and details of patients' immediate, post-operative course. Spearman's rho was used to determine the relationship between non-parametric, continuous variables. Then, a linear regression was performed to assess which variables could predict the peak pain score. Results: A total of 131 patients were included in the study. A non-parametric correlation analysis revealed that maximum pain score was negatively correlated with being male (r = −0.18, p=0.04), age (r = −0.34, p<0.001), and post-op foley placement (r = −0.20, p=0.02) but positively correlated with the preoperative pain score (r = 0.41, p<0.001), time in the PACU (r = 0.19, p = 0.03), and the morphine equivalent dose (MED) of narcotics administered in the PACU (r = 0.67, p<0.001). On linear regression, the significant variables were age, preoperative pain score, and stent placement. For every ten-year increase in age post-operative pain score decreased by 4/10 of a point (p = 0.03). For every 1 point increase in preoperative pain score there was a 3/10 of a point increase in the maximum pain score (p = 0.01), and leaving a stent in place post-operatively was associated with a 1.6 point increase in the maximum pain score. Conclusions: Hydrodistention does not play a role in post-ureteroscopy pain. Patients who are younger, have higher preoperative pain scores, or who are stented will experience more post-operative pain after ureteroscopy.

Semi-rigid ureteroscopic lithotripsy versus laparoscopic ureterolithotomy for large upper ureteral stones: a meta - analysis of randomized controlled trials

ABSTRACT Introduction: To provide a systematic review and meta-analysis of randomized controlled trials (RCT) comparing semi-rigid ureteroscopic lithotripsy (URS) with laparoscopic ureterolithotomy (LU) for the treatment of the large proximal ureteral stone. Materials and methods: A systematic literature review was performed in June 2015 using the PubMed, Scopus, and Web of Science databases to identify relevant studies. Article selection proceeded according to the search strategy based on Preferred Reporting Items for Systematic Reviews and Meta-analysis criteria. Results: Six RCT including 646 patients were analyzed, 325 URS cases (50.3%) and 321 LU cases (49.7%). URS provided a significantly shorter operative time (weighted mean difference [WMD] = −31.26 min; 95%CI −46.88 to −15.64; p<0.0001) and length of hospital stay (WMD = −1.48 days; 95%CI −2.78 to −0.18; p=0.03) than LU. There were no significant differences in terms of overall complications (OR = 0.78; 95%CI 0.21-2.92; p=0.71) and major complications – Clavien ≥3 – (OR = 1.79; 95%CI 0.59-5.42; p=0.30). LU led to a significantly higher initial stone-free rate (OR = 8.65; 95%CI 4.18-17.91; p<0.00001) and final stone-free rate (OR = 6.41; 95%CI 2.24-18.32; p=0.0005) than URS. There was a significantly higher need for auxiliary procedures in URS cases (OR = 6.58; 95%CI 3.42-12.68; p<0.00001). Conclusions: Outcomes with LU for larger proximal ureteral calculi are favorable compared to semi-rigid URS and should be considered as a first-line alternative if flexible ureteroscopy is not available. Utilization of flexible ureteroscopy in conjunction with semi-rigid ureteroscopy may impact these outcomes, and deserves further systematic evaluation.

Dipstick spot urine pH does not accurately represent 24 hour urine PH measured by an electrode

ABSTRACT Objectives To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode. Materials and Methods We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recent pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered an inaccurate result. Results A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588). Conclusions Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH.

Concurrent stone stabilization improves ultrasonic and pneumatic efficacy during cystolithopaxy: an in vitro analysis

Objective To identify whether stabilization of larger bladder stones would improve the efficacy of combination (ultrasonic/pneumatic) lithotripsy in a phantom bladder stone model for percutaneous cystolithopaxy. Materials and Methods Using 1cm phantom Bego stones, a spherical model bladder was used to simulate percutaneous bladder access. A UroNet (US Endoscopy, USA) was placed alongside a Swiss Lithoclast probe through the working channel of a Storz 26Fr rigid nephroscope. Using a 30Fr working sheath, the stone was captured, and fragmented for 60seconds. Resulting fragments and irrigation were filtered through a 1mm strainer, and recorded. Five trials were performed with and without the UN. Durability was then assessed by measuring net defects, and residual grasp strength of each instrument. Descriptive statistics (mean, standard deviations) were used to summarize the data, and Student’s t-tests (alpha<0.05) were used to compare trials. Results The mean time to stone capture was 12s (8-45s). After fragmentation with UN stabilization, there were significant improvements in the amount of residual stone (22% dry weight reduction vs 8.1% without UN, p<0.001), number of fragments (17.5 vs 5.0 frag/stone, p=0.0029), and fragment size (3.6mm vs. 7.05 mm, p=0.035). Mesh defects were noted in all nets, ranging from 2-14 mm, though all but one net retained their original grip strength (36.8N). Conclusions Bladder stone stabilization improved fragmentation when used in conjunction with ultrasonic/pneumatic lithotripsy. However, due to limitations in maneuverability and durability of the UN, other tools need to identified for this indication. .

Tubeless percutaneous nephrolithotomy: outcomes with expanded indications

IntroductionTubeless PCNL has been utilized to shorten hospital stay and improve patient postoperative pain control. Prior studies have excluded those patients with significant bleeding or other complications. Our objective was to evaluate the utility of tubeless PCNL in all patients irrespective of intraoperative outcome.Materials and MethodsA retrospective review of the charts of patients who underwent PCNL at our institute was performed. Patients were assigned to one endourologist who routinely performed tubeless PCNL and to a second endourologist who routinely left a small-bore pigtail nephrostomy. Preoperative demographics operative and postoperative outcomes were compared.ResultsOut of 159 patients included, 83 patients had tubeless PCNL while 76 patients had standard PCNL. There was no difference between groups regarding age, gender, ASA score, number, maximum diameter of stones, number of calyces involved, stone density (HU), laterality and use of preoperative narcotics. While staghorn stones were more common in patients who underwent standard PCNL (p = 0.008). Tubeless patients had less number of access tracts (p ≤ 0.001), shorter hospital stay (1.7 vs. 3.0 days, p = 0.001) when compared to standard PCNL group. Multivariable analysis controlling for confounding factors including staghorn calculi and number of accesses confirmed that tubeless PCNL was associated with shorter hospital stay and less postoperative pain. There was no significant difference in complication rates between the two groups.ConclusionOur report confirms the previous reports of shorter hospital stay, less pain and analgesia as compared to standard PCNL, and establishes its safety irrespective of bleeding, perforation, extravasation or other intraoperative issues that have previously been utilized as exclusionary criteria for this approach.

Does Stone Entrapment With Uro-Net Improve Ho:YAG Laser Lithotripsy Efficiency in Percutaneous Nephrolithotomy and Cystolithopaxy?: an In Vitro Study

Purpose to test the effect of stone entrapment on laser lithotripsy efficiency. Materials and Methods Spherical stone phantoms were created using the BegoStone® plaster. Lithotripsy of one stone (1.0g) per test jar was performed with Ho:YAG laser (365µm fiber; 1 minute/trial). Four laser settings were tested: I-0.8J,8Hz; II-0.2J,50Hz; III-0.5J,50Hz; IV-1.5J,40Hz. Uro-Net (US Endoscopy) deployment was used in 3/9 trials. Post-treatment, stone fragments were strained though a 1mm sieve; after a 7-day drying period fragments and unfragmented stone were weighed. Uro-Net nylon mesh and wire frame resistance were tested (laser fired for 30s). All nets used were evaluated for functionality and strength (compared to 10 new nets). Student's T test was used to compare the studied parameters; significance was set at p < 0.05. Results Laser settings I and II caused less damage to the net overall; the mesh and wire frame had worst injuries with setting IV; setting III had an intermediate outcome; 42% of nets were rendered unusable and excluded from strength analysis. There was no difference in mean strength between used functional nets and non-used devices (8.05 vs. 7.45 lbs, respectively; p = 0.14). Setting IV was the most efficient for lithotripsy (1.9 ± 0.6 mg/s; p < 0.001) with or without net stabilization; setting III was superior to I and II only if a net was not used. conclusions Laser lithotripsy is not optimized by stone entrapment with a net retrieval device which may be damaged by high energy laser settings. .

Flexible ureteroscopy and Holmium:YAG laser lithotripsy for stone disease in patients with bleeding diathesis: a systematic review of the literature

INTRODUCTION AND OBJECTIVES: The management of urolithiasis in patients on anticoagulants presents a challenge to the endourologist. Due to multiple comorbidities, it may be impossible to safely discontinue the anticoagulant treatment. Other modalities such as shock wave lithotripsy and PCNL are contraindicated in these patients, so ureteroscopic treatment may be the only option. We conducted a systematic review of the literature to look at the safety and efficacy of ureteroscopic management in these patients. METHODS: Systematic review and quantitative meta-analysis was performed using studies identified by a systematic electronic literature search from January 1990 to August 2011. All articles reporting on treatment for stones in patients with a bleeding diathesis using ureteroscopy and a Holmium:YAG laser were included. Two reviewers independently extracted the data from each study. The data was included into a meta-analysis and discussed. RESULTS: Three studies were identified reporting on 70 patients (73 procedures). All patients had stone fragmentation using Holmium laser. The mean stone size was 13.2mm with a range of 5-35mm. The quality of the included studies was modest. Stone free status was achieved in sixty-four patients (87.7%). There were no major complications and only 11% of the patients developed minor complications with only 4% rate of minor bleeding. CONCLUSIONS: Retrograde stone treatment using ureteroscopy and holmium laser lithotripsy can be safely performed in patients with bleeding diathesis with a low complication rate.

Use of traditional Chinese medicine in the management of urinary stone disease: [review]

Objective: To assess the evidence-based literature supporting the use of traditional Chinese medicine Kampo herbal and Acupuncture in stone disease management. Materials and Methods: Four of the most commonly used herbal components of Kampo medicine in the treatment of stone disease are described according to their in vitro and in vivo effects. We also reviewed the role of Acupuncture in urologic clinical setting as well as its proposed mechanisms of action and results. Medline database was assessed using isolated and conjugated key words (Chinese Medicine, Kampo, Chinese Herbal, Calculi, Stone Disease, Kidney, Acupuncture, Herbal Medicine). Articles were reviewed and summarized. Results: Herbal medicine has been proven to be free from side-effects and therefore suitable for long term use therapy. Its antilithic beneficial effects include increased urinary volume, increased magnesium excretion (Takusya), inhibitory activity on calcium oxalate aggregation (Takusya, Wulingsan and Desmodyum styracyfolium), inhibition of calcium oxalate nucleation and hydroxyapatite internalization (Wulingsan). In contrast, acupuncture, has shown to be effective as a pre-treatment anxiolytic and analgesic during colic pain and extracorporeal shock wave lithotripsy treatment, reducing the need for complementary sedative drugs. Conclusion: Chinese traditional medicine is promising as regards its role in stone prevention. An effort must be made in order to standardize study protocols to better assess acupuncture results since each procedure differs in regards to selected acupoints, electrostimulation technique and adjunct anesthetics. Similarly, standardization of Kampo formulations and acceptable clinical endpoints (imaging vs. symptomatic events) is needed.

Urethral catheter insertion forces: a comparison of experience and training

Purpose: This study was undertaken to evaluate the insertion forces utilized during simulated placement of a urethral catheter by healthcare individuals with a variety of catheter experience. Materials and Methods: A 21F urethral catheter was mounted to a metal spring. Participants were asked to press the tubing spring against a force gauge and stop when they met a level of resistance that would typically make them terminate a catheter placement. Simulated catheter insertion was repeated fives times, and peak compression forces were recorded. Healthcare professionals were divided into six groups according to their title: urology staff, non-urology staff, urology resident/ fellow, non-urology resident/ fellow, medical student, and registered nurse. Results: A total of fifty-seven healthcare professionals participated in the study. Urology staff (n = 6) had the lowest average insertion force for any group at 6.8 ± 2.0 Newtons (N). Medical students (n = 10) had the least amount of experience (1 ± 0 years) and the highest average insertion force range of 10.1 ± 3.7 N. Health care workers with greater than 25 years experience used significantly less force during catheter insertions (4.9 ± 1.8 N) compared to all groups (p < 0.01). Conclusions: We propose the maximum force that should be utilized during urethral catheter insertion is 5 Newtons. This force deserves validation in a larger population and should be considered when designing urethral catheters or creating catheter simulators. Understanding urethral catheter insertion forces may also aid in establishing competency parameters for health care professionals in training.

Radial dilation of nephrostomy balloons: a comparative analysis

PURPOSE: The dynamics of percutaneous balloon expansion may differ with increasing extrinsic compressive forces and increasing inflation pressures. This study compares the ability of percutaneous balloons to expand under different radial constrictive forces. MATERIALS AND METHODS: Three 30F nephrostomy balloons were tested: Bard X-Force™, Boston Scientific Microvasive Amplatz Tractmaster™, and Cook Ultraxx™. With a super stiff guidewire in place, the balloon tip was secured by elevated vice grips on either side of the balloon. A string was wrapped around the balloon center once, and incremental increases in load were added (2g, 42g, 82g, and 122g) to represent increasing extrinsic compression. The balloon was inflated with a contrast agent and circumference changes were measured at increments of 4 ATM, 10 ATM, and burst pressure. Balloons were tested in triplicate for each load. RESULTS: All balloons were unable to reach 90 percent of their expected diameter with larger constrictive loads (122g) at low (4 ATM) and nominal (10 ATM) inflation pressures. Only the Bard and Cook balloons reached at least 90 percent of the expected diameter with a coefficient of variance (CV) less than 10 percent at burst pressure under the larger constrictive load (122g), 94.3 percent ± 6.7 percent, CV 7.1 percent and 96.3 percent ± 2.9 percent, CV 3.0 percent respectively. All balloons performed well under low constriction forces and reached at least 80 percent of the expected diameter by 10 ATM under all constrictive loads. CONCLUSIONS: The Bard X-Force and Cook Ultraxx percutaneous nephrostomy balloons achieved the most reliable radial dilation against large constrictive forces simulating fascial or retroperitoneal scar tissue.

The length of the male urethra

PURPOSE: Catheter-based medical devices are an important component of the urologic armamentarium. To our knowledge, there is no population-based data regarding normal male urethral length. We evaluated the length of the urethra in men with normal genitourinary anatomy undergoing either Foley catheter removal or standard cystoscopy. MATERIALS AND METHODS: Male urethral length was obtained in 109 men. After study permission was obtained, the subject's penis was placed on a gentle stretch and the catheter was marked at the tip of the penis. The catheter was then removed and the distance from the mark to the beginning of the re-inflated balloon was measured. Alternatively, urethral length was measured at the time of cystoscopy, on removal of the cystoscope. Data on age, weight, and height was obtained in patients when possible. RESULTS: The mean urethral length was 22.3 cm with a standard deviation of 2.4 cm. Urethral length varied between 15 cm and 29 cm. No statistically significant correlation was found between urethral length and height, weight, body mass index (BMI), or age. CONCLUSIONS: Literature documenting the length of the normal male adult urethra is scarce. Our data adds to basic anatomic information of the male urethra and may be used to optimize genitourinary device design.