Bodo E. Knudsen

The use of stents in contemporary urology.

Purpose of review Ureteral stents are a mainstay of todays urological armamentarium. This review critically evaluates the recent literature and provides a concise summary of the use of stents in urology today. While stents are used in many reconstructive urologic procedures, this review focuses on the use of stents in urolithiasis as it pertains to ureteroscopy, shockwave lithotripsy, and ureteropelvic junction obstruction. Recent findings Ureteral stents are associated with irritative symptoms, hematuria, infection, and encrustation. A new validated quality of life and impact questionnaire has been developed and has shown that 76% of patients suffer at least some type of morbidity related to the stent. Many studies in the recent literature have re-examined our use of stents today. For example, concepts regarding stenting following ureteroscopy, before shockwave lithotripsy, and following endopyelotomy have undergone an evolution based on the results of randomized, prospective studies. Summary The ureteral stent is an invaluable urological tool and its indications are evolving as are new stent technologies to improve patient care and comfort.

Durability of the Next-generation Flexible Fiberoptic Ureteroscopes: A Randomized Prospective Multi-institutional Clinical Trial

OBJECTIVES To evaluate the durability of 4 next-generation flexible ureteroscopes in a randomized, multi-institutional, prospective study. METHODS Patients at 3 institutions were randomized to 1 of 4 flexible ureteroscopes: the Wolf Viper, Olympus URF-P5, Gyrus-ACMI DUR-8 Elite (DUR-8E), and Stryker FlexVision U-500. Each center used 1 scope from each manufacturer until it needed major repair (primary endpoint). Intraoperative data included total time of use, number of scope insertions through an access sheath, working time in the lower pole, number of insertions and total time for accessory instrumentation in the working channel, number of laser insertions through the working channel, and total laser energy used. RESULTS A total of 175 patients were randomized. The DUR-8E experienced early catastrophic failure (< or = 10 cases) at all 3 sites; however, this also occurred at 1 site each for the Stryker and Wolf scopes. The DUR-8E required major repair after the fewest average number of cases (5.3), the lowest average total time of usage (108 minutes), the fewest insertions through an access sheath (20.3), the shortest duration of laser firing (31.3 minutes), and the shortest instrument in the working channel time (224.7 minutes). As such, due to variation in durability within manufacturers, no differences could be demonstrated. Visibility ratings for the Wolf iper were significantly better than the DUR-8E (P = .034) and the Flexvision (P = .038). CONCLUSIONS The Wolf Viper, Olympus URF-P5, and Stryker Flexvision U-500 flexible ureteroscopes seem comparable with regard to durability. However, larger prospective registry-based studies are needed to document significant differences between them.

Triclosan Loaded Ureteral Stents Decrease Proteus Mirabilis 296 Infection in a Rabbit Urinary Tract Infection Model

PURPOSE Infection and encrustation remain major limitations of ureteral stent use and to our knowledge no device has completely overcome these obstacles to date. Triclosan is a biocide currently used in a plethora of consumer and medical products that has recently been loaded into a ureteral stent. Using a rabbit model of UTI we examined the effects of triclosan impregnated stent segments on the growth and survival of Proteus mirabilis, a uropathogen commonly associated with device related UTI and encrustation. MATERIALS AND METHODS A total of 48 male New Zealand White rabbits were instilled transurethrally with 1 x 10(6) P. mirabilis 296. A stent curl from a triclosan eluting, Percuflex Plus or Optima ureteral stent was placed intravesically. Urine was cultured on days 1, 3 and 7. On day 7 the stents were assessed for encrustation and viable organisms, while the bladders were scored for the degree of inflammation. RESULTS Throughout the study urine isolated from the triclosan group contained significantly fewer viable organisms than controls with 7 of 13 animals completely clearing the infection by day 7. Similarly 9 of 13 triclosan eluting stents showed no viable organisms upon recovery and the remaining 4 showed significantly fewer organisms than controls. Urine and stents in all controls were positive for P. mirabilis at all time points. Although there was no significant difference in encrustation among the groups, bladders harvested from the triclosan group demonstrated significantly less inflammation. CONCLUSIONS Triclosan eluting stents greatly decreased P. mirabilis growth and survival in a rabbit UTI model compared to controls. These stents may prove useful for decreasing device related P. mirabilis UTIs.

Advances in Ureteral Stent Design

BACKGROUND AND PURPOSE Ureteral stents are widely used in patients with urologic disorders. This review critically evaluates the recent literature, providing an update on advances in the development and design of stents. METHODS A thorough MEDLINE and PubMed literature search on ureteral stents was performed, and all pertinent articles were reviewed in detail. This review was formulated on the basis of these articles, encompassing both basic science and clinical aspects of advances in ureteral stent design. RESULTS The advances in development and design have been directed primarily toward decreasing stent-related morbidity such as discomfort, bladder irritability, infection, encrustation, and the need for an additional cystoscopic procedure to remove the stent. In recent years, there have been many significant advances in the design of ureteral stents, including tapered distal ends, and construction, such as magnetic, biodegradable, and tissue-engineered materials. CONCLUSIONS There are many different bulk materials and coatings available for the manufacturing of ureteral stents, many of which are new. However, the ideal biomaterial has yet to be discovered. With ongoing research in this area, further advances in ureteral stent design will continue to improve outcomes for patients who require stents. Future advances are likely to include drug-coated stents, drug-eluting stents, and localized stenting techniques such as endoluminal gel paving.

Silodosin to Facilitate Passage of Ureteral Stones: A Multi-institutional, Randomized, Double-blinded, Placebo-controlled Trial

BACKGROUND Using a selective α-blocker for medical expulsive therapy (MET) is a cost-effective treatment approach widely used for ureteral stones. OBJECTIVE To evaluate the efficacy of silodosin, a selective α-1a receptor antagonist, in this setting. DESIGN, SETTING, AND PARTICIPANTS This was a multicenter, phase 2 study conducted in adult patients with a unilateral ureteral calculus of 4-10mm. Of 239 patients in the safety population, six discontinued due to adverse events. INTERVENTION Patients were randomized 1:1 to receive silodosin 8 mg or placebo for up to 4 wk. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS The primary outcome was spontaneous stone passage, analyzed using logistic regression. Secondary outcomes included time to stone passage, emergency room (ER) visits, hospital admissions, analgesic use, and incidence and severity of pain. RESULTS AND LIMITATIONS No significant differences between the silodosin and placebo groups were observed for passage rate of all stones (52% vs 44%, respectively; p=0.2). However, silodosin achieved a significantly greater rate of distal ureter stone passage than placebo (p=0.01). Significant differences were not observed for ER visits, hospital admission, or use of analgesics. The number of patients in the intent-to-treat population was slightly below the calculated sample size (232 vs 240) and sample sizes were not calculated for subgroup analyses. CONCLUSIONS This is among the first prospective, randomized, multi-institutional trials to examine the efficacy of a selective α-1a antagonist as MET in patients with ureteral calculi and did not demonstrate a benefit to the entire ureter. However, silodosin was found to be well tolerated and beneficial in facilitating the passage of distal ureteral stones, warranting additional future studies on distal stone elimination. PATIENT SUMMARY In this report, we looked at the efficacy of silodosin for the treatment of ureteral stones. We found that silodosin increased passage of distal ureteral stones.

Stenting after ureteroscopy: pros and cons

The results of the numerous trials evaluating stenting after uncomplicated ureteroscopy suggest that the routine placement of a stent is no longer necessary. Patients with stents seem to have significantly more pain and irritative voiding symptoms. In addition, the routine placement of a stent significantly adds to the overall cost of the procedure. There is a subgroup of patients who would likely benefit from a stent as evidenced by the higher readmission to hospital rate than in nonstented patients. Ideally, future trials will help unmask a method to identify these patients.

Multicenter Experience with Metallic Ureteral Stents for Malignant and Chronic Benign Ureteral Obstruction

BACKGROUND AND PURPOSE A new coil-based metallic ureteral stent offers greater radial strength with longer indwelling time compared with plastic stents. This multicenter retrospective study reviews the clinical experience with this stent for malignant or benign chronic ureteral obstruction. PATIENTS AND METHODS Patients had stent placement in a retrograde fashion. We analyzed preplacement and postplacement renal imaging to determine degree of hydronephrosis. Stent encrustation was determined by either visual inspection at the time of stent change or plain abdominal radiography. Preoperative and follow-up serum creatinine values were compared for each patient. RESULTS A total of 76 stents in 59 renal units (40 patients) were successfully placed. Creatinine value follow-up on 54 renal units showed 20 (37%) units to have stable, 15 (28%) improved, and 19 (35%) with worsening values. No stent showed encrustation on plain radiography despite it being seen on two during direct visualization. Three stents needed operative removal with either percutaneous nephrolithotomy or cystolitholapaxy. Fifteen of 41 (37%) metallic stents placed because of an obstructed plastic stent also became obstructed. At last follow-up, 6 of 40 patients were kept from nephrostomy tubes because of the metallic stent. CONCLUSIONS Metallic stents are a viable alternative to nephrostomy tubes in patients in whom conventional stents fail because of malignant obstruction, but patients need to be followed closely. Stent encrustation that resulted in retained stents was poorly visualized on plain radiography. Patients still remain at risk for obstruction, urinary tract infections, and lower urinary tract symptoms from the metallic stent.

Quantification of holmium:yttrium aluminum garnet optical tip degradation.

INTRODUCTION Optical laser fibers are utilized to transmit energy to the surface of a stone during holmium:yttrium aluminum garnet (Ho:YAG) laser lithotripsy. During lithotripsy, fiber tip degradation (burn back) can occur. Fiber burn back may diminish fragmentation efficiency, increase operative time, and increase cost because of fiber replacement. We hypothesize that fiber tip degradation (burn back) varies among different commercially available Ho:YAG laser fibers. METHODS Fibers of varying core diameter sizes for Ho:YAG lithotripsy were evaluated from different manufacturers. Fibers were cleaved, stripped, polished, and inspected for tip uniformity. Fibers were initially tested without contact followed by contact testing using artificial Bego stones. Pre- and postcontact energy outputs were measured by energy detector. Distal tip degradation (burn back) was measured by digital micrometer. Testing was performed on two Ho:YAG lasers (Lumenis VersaPulse 100W and Dornier Medilas H20). All fibers were tested while submerged in water. RESULTS No burn back was observed in any fiber tested in still water (without contact). Before and after lithotripsy, a trend existed with fibers demonstrating high burn back and high preablation energy outputs. The majority of these fibers were <300 microm diameter. Conversely, fibers with low burn back showed low preablation energy outputs and were >300 microm diameter. CONCLUSION Fiber burn back and energy transmission varied among the fibers tested. Burn back only occurred during lithotripsy. Burn back may be reduced by fiber selection or using low pulse energy. Fiber burn back may affect the efficiency of fragmentation and contribute to decreased longevity of the fiber.

Ultrasonic, Pneumatic and Combination Intracorporeal Lithotripsy for Percutaneous Nephrolithotomy

INTRODUCTION Refinements in ultrasonic and pneumatic lithotriptors, as well as the development of new dual-modality lithotriptors, have increased the options available for the endourologist. Studies comparing the efficiency of the devices in both bench and clinical models help provide the endourologist with guidance in selecting the most appropriate lithotrite. METHODS A review of the literature was performed reviewing the current status of pneumatic, ultrasonic, and dual-modality lithotriptors. RESULTS Performance characteristics of currently available lithotriptors differ. Dual-modality lithotriptors offer superior efficiency compared to separate ultrasonic and pneumatic lithotriptors but durability may be a concern with some models. CONCLUSIONS Ultrasonic and pneumatic devices are the lithotriptors of choice for PCNL. Dual-modality lithotriptors have been shown to be the most efficient in both bench and limited clinical trials.

Holmium:Yttrium-Aluminum-Garnet Lithotripsy Proximal Fiber Failures From Laser and Fiber Mismatch

OBJECTIVES To document proximal fiber failures at the subminiature version A connector during holmium:yttrium-aluminum-garnet lithotripsy when fibers and lasers are mismatched. METHODS Optical fibers supplied by Trimedyne were coupled to holmium:yttrium-aluminum-garnet lasers from Lumenis (VersaPulse 100 W), New Star (NS1500 12 W), and Dornier (Medilas H20) for an in vitro experiment. We reviewed the operating room laser log for our Lumenis VersaPulse 100 W laser for an in vivo experiment. The lasers were maintained with the rods aligned. The use of a different brand, small caliber (diameter less than 300 microm) and larger fibers and the number of proximal fiber failures were recorded. RESULTS The in vitro experiment was stopped prematurely because the fiber failed on the New Star laser with an audible explosion sound and smoke emanating from the connector end. The fiber could not be extracted from the laser. The fiber at its connector end had melted and fused to the laser terminal. In vivo, 4% of all cases using the sub-300-microm fibers had connector end failures versus 0% of 365-microm fibers, and 0% of 550-microm fibers (P <0.001). Of 188 consecutive cases using the sub-300-microm fibers, 4 (13%) of 30 cases had connector end failures using the Trimedyne fiber versus 3 (2%) of 155 cases using the Lumenis fiber (P <0.01). CONCLUSIONS The mismatch of small-caliber fibers with lasers runs the risk of fiber failure, energy reflected back at the laser, and laser damage. Urologists should familiarize themselves with the specifications of their holmium:yttrium-aluminum-garnet lasers and fibers to avoid expensive laser repairs.