Comparison of Radiation Exposure from Fixed Table Fluoroscopy to a Portable C-Arm During Ureteroscopy.

INTRODUCTION: Current treatment practices within the field of endourology require the routine use of radiation exposure to provide adequate imaging during urologic procedures. One such procedure requiring repeated radiation exposure during treatment is ureteroscopy. We set out to compare estimated fluoroscopic radiation exposures employing fixed table and portable C-arm fluoroscopy. MATERIALS AND METHODS: A cross-sectional dosimetry phantom model was placed supine on both fixed fluoroscopy and standard operating room tables. The models were then exposed to three separate 5-minute runs of fluoroscopic exposure. Metal oxide semiconductor field effect transistor dosimeters were utilized in organ-specific locations to determine specific radiation exposure dosages. Absorbed radiation was determined for each organ location for both fluoroscopy units. Organ dose volumetric corrections were performed for skin and red bone marrow, to correct for the nonirradiated portion. Organ dose rate (ODR, mGy/s) and effective dose rate (EDR, mSv/s) were calculated, with values reported as mean ± standard deviation. RESULTS: There were found to be statistically significant elevations for both total EDR and organ-specific dose rates with the use of fixed table fluoroscopy compared with C-arm fluoroscopy. EDR was found to be 0.0240 ± 0.0019 mSv/s for the fixed table unit and 0.0029 ± 0.0005 mSv/s for the C-arm unit (p = 0.0024). Internal organs exposed to the most radiation during fixed table fluoroscopy included the gall bladder and stomach in comparison to C-arm fluoroscopy, which found elevated exposure in the kidneys, pancreas, and spleen. CONCLUSION: The routine use of fixed table fluoroscopy results in significantly elevated estimated organ doses and EDR when directly compared with C-arm fluoroscopy in model trials. This difference should be taken into consideration by practicing urologists when patient treatment requires the use of fluoroscopy to maintain radiation exposure as low as reasonably achievable.

Should metabolic evaluation be performed in patients with struvite stones?

Previous studies suggested that patients with pure struvite calculi rarely have underlying metabolic abnormalities. Therefore, most of these patients do not undergo metabolic studies. We report our experience with these patients and their response to directed medical therapy. Between 1/2005 and 9/2012, 75 patients treated with percutaneous nephrolithotomy for struvite stones were identified. Of these, 7 had pure struvite stones (Group 1), 32 had mixed struvite stones (Group 2), both with metabolic evaluation, and 17 had pure struvite stones without metabolic evaluation (Group 3). The frequency of metabolic abnormalities and stone activity (defined as stone growth or stone-related events) was compared between groups. The median age was 55 years and 64 % were female. No significant difference in race, infection history, family history, stone location or volume existed between groups. Metabolic abnormalities were found in 57 % of Group 1 and 81 % of Group 2 patients. A similar proportion of Group 1 and 2 patients received modification to or continuation of metabolic therapy, whereas no Group 3 patients received any directed therapy. In patients with >6 months follow-up, the stone activity rate between Groups 1 and 2 appeared similar whereas Group 3 trended towards higher stone activity rate. Metabolic abnormalities in pure struvite stone formers appear to be more common than previously reported. Directed medical therapy in these patients may reduce stone activity. The role of metabolic evaluation and directed medical therapy needs reconsideration in patients with pure struvite stones.

Digital Tomosynthesis: A Viable Alternative to Noncontrast Computed Tomography for the Follow-Up of Nephrolithiasis?

OBJECTIVE: Digital tomosynthesis (DT) is a new X-ray-based imaging technique that allows image enhancement with minimal increase in radiation exposure. The purpose of this study was to compare DT with noncontrast computed tomography (NCCT) and to evaluate its potential role for the follow-up of patients with nephrolithiasis in a nonemergent setting. METHODS: A retrospective review of patients with nephrolithiasis at our institution that underwent NCCT and DT from July 2012 to September 2013 was performed. Renal units (RUs) that did not undergo treatment or stone passage were randomly assigned to two blinded readers, who recorded stone count, size area (mm(2)), maximum stone length (mm), and location, for both DT and NCCT. Mean differences per RU were compared. Potential variables affecting stone detection rate, including stone size and body mass index (BMI), were evaluated. Interobserver agreement was determined using the intraclass correlation coefficient to measure the consistency of measurements made by the readers. RESULTS: DT and NCCT demonstrated similar stone detection rates in terms of stone counts and stone area mm(2). Of the 79 RUs assessed, 41 RUs showed exact stone counts on DT and NCCT. The mean difference in stone area was 16.5 mm(2) (-4.6 to 38.5), p = 0.121. The mean size of the largest stone on NCCT and DT was 9.27 and 8.87 mm, respectively. Stone size and BMI did not cause a significant difference in stone detection rates. Interobserver agreement showed a strong correlation between readers and adequate reproducibility. CONCLUSION: We found DT to be a comparable imaging modality to NCCT for the detection of intrarenal stones, without a significant effect from stone size and BMI and adequate reproducibility between multiple readers. DT appears to be an ideal alternative for following patients with nephrolithiasis due to its acceptable stone detection rates, low radiation exposure, and decreased cost compared to NCCT.

Radiation Dosimetry for Ureteroscopy Patients: A Phantom Study Comparing the Standard and Obese Patient Models.

PURPOSE: To determine the effect of obesity on radiation exposure during simulated ureteroscopy. METHODS: A validated anthropomorphic adult male phantom with a body mass index (BMI) of approximately 24 kg/m(2), was positioned to simulate ureteroscopy. Padding with radiographic characteristics of human fat was placed around the phantom to create an obese model with BMI of 30 kg/m(2). Metal oxide semiconductor field effect transistor (MOSFET) dosimeters were placed at 20 organ locations in both models to measure organ dosages. A portable C-arm was used to provide fluoroscopic x-ray radiation to simulate ureteroscopy. Organ dose rates were calculated by dividing organ dose by fluoroscopy time. Effective dose rate (EDR, mSv/sec) was calculated as the sum of organ dose rates multiplied by corresponding ICRP 103 tissue weighting factors. RESULTS: The mean EDR was significantly increased during left ureteroscopy in the obese model at 0.0092 ± 0.0004 mSv/sec compared with 0.0041 ± 0.0003 mSv/sec in the nonobese model (P < 0.01), as well as during right ureteroscopy at 0.0061 ± 0.0002 and 0.0036 ± 0.0007 mSv/sec in the obese and nonobese model, respectively (P < 0.01). EDR during left ureteroscopy was significantly greater than right ureteroscopy in the obese model (P = 0.02). CONCLUSIONS: Fluoroscopy during ureteroscopy contributes to the overall radiation dose for patients being treated for nephrolithiasis. Obese patients are at even higher risk because of increased exposure rates during fluoroscopy. Every effort should be made to minimize the amount of fluoroscopy used during ureteroscopy, especially with obese patients.

Evaluation of Novel Ball-Tip Holmium Laser Fiber: Impact on Ureteroscope Performance and Fragmentation Efficiency.

PURPOSE: A novel ball tip (BT) holmium laser fiber has recently been developed, which features a modified rounded tip. The modification is purported to aid in insertion and minimize damage to the ureteroscope working channel. We evaluated this laser fiber with regard to stone comminution, tip degradation, insertional force into the ureteroscope, and impact on ureteroscope deflection. MATERIALS AND METHODS: A 242 µm BT fiber and a standard flat tip (SF) fiber were compared. Four kilojoules was delivered to a BegoStone over a constant surface area using settings of 0.2/50, 0.6/6, 0.8/8, and 1 J/10 Hz. Fiber tip degradation was measured at 1 and 4 kJ. Ureteroscope deflection was measured with the Olympus URF-P5, URF-P6, and URF-V. Insertion force into a 270° angled ureteroscope sheath model was measured. RESULTS: A sample size of five fibers was used for each comminution energy setting. Comminution increased with pulse energy without significant difference between fibers. No significant differences in tip degradation were observed. Both fibers reduced deflection (10°-30°) in all ureteroscopes without significant differences between fibers. Four new fibers paired with new sheath models were used to test insertion force. The BT insertion forces were approximately one-third of the SF. One SF fiber caused significant damage to the sheath and could not be advanced completely. CONCLUSIONS: The BT fiber has comparable comminution, tip degradation, and ureteroscope deflection performance compared with the SF fiber while exhibiting reduced insertion force within an aggressively deflected working sheath. The new tip design is likely protective of the working channel without loss of performance.

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

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

Clinical outcomes after ureteroscopic lithotripsy in patients who initially presented with urosepsis: matched pair comparison with elective ureteroscopy.

BACKGROUND AND PURPOSE: The outcomes of ureteroscopy (URS) after urgent decompression and antibiotics for patients who initially present with urosepsis because of obstructive urolithiasis have not been previously evaluated. The aim of this study was to compare the outcomes and complications of URS in patients with a recent history of sepsis with those without sepsis. METHODS: The study included 138 patients who underwent URS for stone removal from January 2004 to September 2011 at a university medical center. A matched-pair analysis was performed using three parameters (age, sex, and race) to compare outcomes and complications between 69 patients who had sepsis vs a matched cohort who did not have sepsis before URS. RESULTS: The study included 138 patients, 88 (64%) females and 50 (36%) males with a median age of 57.5 years (range 18-88 years). Patients with previous sepsis had similar patient characteristics and stone-free rates (81% vs 77%) compared with patients without previous sepsis (P>0.05). Patients with previous sepsis, however, had a significantly higher complications rate (20% vs 7%), longer hospital length of stay (LOS), and longer courses of postoperative antibiotics after URS (P<0.05). Sepsis developed postoperatively in two patients with diabetes (one with and one without previous sepsis), and postoperative fever developed in five patients with previous sepsis. CONCLUSIONS: URS after decompression for urolithiasis-related sepsis has similar success but higher complication rates, greater LOS, and longer course of postoperative antibiotics. This is important in counseling patients who present for definitive URS after urgent decompression for urolithiasis-related sepsis.

The influence of nerve conduits diameter in motor nerve recovery after segmental nerve repair.

Many conduits have demonstrated potential to substitute nerve autografts; however, the influence of conduit inner diameter (ID) has never been studied as a separate parameter. This experimental study compared motor recovery after segmental nerve repair with two different ID collagen conduits: 1.5 and 2.0 mm. In addition, the conduits were analyzed in vitro to determine the variations of ID before and after hydration. Thirty rats were divided into three groups: 2.0 mm ID, 1.5 mm ID, and a control group autograft. After 12 weeks, the 1.5 mm ID group demonstrated significant increase in force (P < 0.0001) and weight (P < 0.0001) of the tibialis anterior muscle and better histomorphometry results of the peroneal nerve (P < 0.05) compared to 2.0 mm ID group; nevertheless, autograft results outperformed both conduits (P < 0.0001). Conduits ID were somewhat smaller than advertised, measuring 1.59 ± 0.03 mm and 1.25 ± 0.0 mm. Only the larger conduit showed a 6% increase in ID after hydration, changing to 1.69 ± 0.02 mm. Although autografts perform best, an improvement in motor recovery can be achieved with collagen conduits when a better size match conduit is being used. Minimal changes in collagen conduits ID can be expected after implantation.

Treatment of a segmental nerve defect in the rat with use of bioabsorbable synthetic nerve conduits: a comparison of commercially available conduits.

BACKGROUND: The use of biodegradable synthetic nerve conduits for the reconstruction of segmental nerve defects has been extensively reported in both animal and human studies, with a majority of studies evaluating sensory nerve recovery. However, few studies have compared these nerve conduits for functional motor recovery. The purpose of this study was to compare three commercially available, synthetic, bioabsorbable nerve conduits and autograft with respect to compound muscle action potentials, maximum isometric tetanic force, wet muscle weight, and nerve histomorphometry. METHODS: Eighty Lewis rats were divided into four groups according to the type of repair of a 10-mm excision of the sciatic nerve: group I had a reversed autograft; group II, a poly-DL-lactide-epsilon-caprolactone conduit; group III, a type-I collagen conduit; and group IV, a polyglycolic acid conduit. All results were compared with the contralateral side. At twelve weeks, the rats underwent bilateral measurements of the compound muscle action potentials of the tibialis anterior and flexor digiti quinti brevis muscles, isometric tetanic force and muscle weight of the tibialis anterior, and peroneal nerve histomorphometry. RESULTS: At twelve weeks, no difference in the percentage of recovery between the autograft and the poly-DL-lactide-epsilon-caprolactone conduit was observed with respect to compound muscle action potentials, isometric muscle force, muscle weight, and axon count measurements. The poly-DL-lactide-epsilon-caprolactone and collagen conduits remained structurally stable at twelve weeks, while the polyglycolic acid conduits had completely collapsed. The polyglycolic acid conduit had the poorest results, with a recovery rate of 15% for compound muscle action potentials and 29% for muscle force. CONCLUSIONS: The functional outcome in this rat model was similar for the autograft and the poly-DL-lactide-epsilon-caprolactone conduits when they were used to reconstruct a 10-mm sciatic nerve defect. Functional recovery following the use of the polyglycolic acid conduit was the poorest.

Isometric tetanic force measurement method of the tibialis anterior in the rat.

Tetanic force measurements of rat tibialis anterior (TA) muscles have been described, but with a variety of stimulation parameters. This study presents a novel functional method of force measurement of the rat TA muscle and describes the optimization of stimulation parameters. Bilateral TA muscles in 10 male Lewis rats were attached to a force transducer after the corresponding hindlimb was fixed. Preload, stimulus intensity, duration, and frequency were optimized for each individual muscle and the isometric maximal tetanic muscle force was measured. The mean left side tetanic force as a percentage of the right was 100.0 +/- 4.4% and was statistically equivalent. Large standard deviations between sides (35-50%) were observed in the optimized parameters (preload, stimulus intensity, duration, and frequency). Optimization of the variables affecting isometric tetanic force resulted in reproducible and reliable side-to-side measurements of the TA muscle in the rat model.

Mechanical properties of intrasynovial and extrasynovial tendon fascicles.

BACKGROUND: Tendon grafting in tendon reconstruction often involves the interchange of intrasynovial and extrasynovial tendons. Although many studies have examined the cellular and biological differences between tendons of various sources, few have studied the mechanical properties of these two different types of tendons. The purpose of this study was to investigate the mechanical properties of intrasynovial and extrasynovial tendons. METHODS: Canine peroneus longus (extrasynovial) and flexor digitorum profundus (intrasynovial) tendons, further subdivided into intrasynovial tendinous and intrasynovial fibrocartilaginous segments, were used in the study. An indentation test was used to measure the compressive modulus. Tensile testing was performed on 400mum longitudinal sections. FINDINGS: The compressive modulus of the intrasynovial fibrocartilaginous segment was significantly higher than that of the intrasynovial tendinous segment, which was in turn significantly higher than that of the extrasynovial tendon (P<0.0001). The tensile modulus of extrasynovial tendon was significantly higher than that of intrasynovial fibrocartilaginous and intrasynovial tendinous segments (P<0.005). The tensile modulus of the intrasynovial fibrocartilaginous and tendinous segments was not significantly different (P=0.14). INTERPRETATION: The results suggest that extrasynovial tendons exhibit superior tensile properties but inferior compressive properties when compared to intrasynovial tendons, which is consistent with their biological role in situ, but which could lead to complications when these tendons are repositioned during tendon graft surgery.

The superficial inferior epigastric artery fascia flap in the rabbit.

In reconstructive surgery, fascial flaps provide thin, pliable tissue for mucosal closure or serve as a highly vascularized support for skin grafts. Their angiogenic potential is used for experimental neovascularization of avascular tissue grafts. However, most fascial flaps in animal surgery have random pattern design with short reach. As a pilot study for a femur revascularization project in rabbits, a new axial fascial flap is described based on the superficial inferior epigastric (SIE) vessels. They were used in this species previously only as ligated bundles or in fasciocutaneous flaps. The topographical anatomy of the SIE-vessels, lower abdominal fascia, and panniculus carnosus are outlined. The angiogenic capabilities are demonstrated microangiographically by abundant vessel formation in a femur allograft. Used in a pedicled fashion, this flap is an alternative to femoral and saphenous vessels for prefabrication or revascularization procedures in the lower abdomen, genital area, and thigh. Distant recipient sites seem possible with microsurgical transfer.