Ben H. Chew

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

PURPOSEnInfection 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.nnnMATERIALS AND METHODSnA 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.nnnRESULTSnThroughout 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.nnnCONCLUSIONSnTriclosan 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.

Technology Insight: novel ureteral stent materials and designs

Ureteral stents are an important tool for aiding upper urinary tract drainage, but can cause significant patient morbidity. Common problems include stent-induced pain, hematuria, dysuria, infection, and encrustation. From a urologists perspective, stents must be easy to maneuver in the urinary tract, radiopaque, and affordable. Since the development of the modern day stent in 1978, stents have evolved to include softer biomaterials that are more resistant to encrustation and infection. An ideal biomaterial is one that is not affected by its environment and does not elicit reactive changes in surrounding tissues. To date, the ideal biomaterial or stent does not exist. This review discusses developments that address the issues of infection, biofilm formation, encrustation, and patient comfort. Stent materials including polyurethane, silicone, biodegradable substances and new combination polymers are reviewed, in addition to novel stent coatings such as heparin, hydrogel, and silver nitrate. Ureteral stent technologies currently lag behind vascular stents, particularly drug-eluting stents, but new developments will continue to improve these essential urological tools.

Comparison of the thermal and histopathological effects of bipolar and monopolar electrosurgical resection of the prostate in a canine model

To compare the thermal and histopathological effects of two commercially available bipolar systems and conventional monopolar transurethral resection of the prostate (TURP) in a canine model. Bipolar TURP is an alternative to monopolar electrosurgery for treating benign prostatic hyperplasia and has several potential clinical advantages, including the ability to use normal saline irrigation, enhanced haemostasis and less collateral thermal damage.

3D segmentation of kidney tumors from freehand 2D ultrasound

To completely remove a tumor from a diseased kidney, while minimizing the resection of healthy tissue, the surgeon must be able to accurately determine its location, size and shape. Currently, the surgeon mentally estimates these parameters by examining pre-operative Computed Tomography (CT) images of the patients anatomy. However, these images do not reflect the state of the abdomen or organ during surgery. Furthermore, these images can be difficult to place in proper clinical context. We propose using Ultrasound (US) to acquire images of the tumor and the surrounding tissues in real-time, then segmenting these US images to present the tumor as a three dimensional (3D) surface. Given the common use of laparoscopic procedures that inhibit the range of motion of the operator, we propose segmenting arbitrarily placed and oriented US slices individually using a tracked US probe. Given the known location and orientation of the US probe, we can assign 3D coordinates to the segmented slices and use them as input to a 3D surface reconstruction algorithm. We have implemented two approaches for 3D segmentation from freehand 2D ultrasound. Each approach was evaluated on a tissue-mimicking phantom of a kidney tumor. The performance of our approach was determined by measuring RMS surface error between the segmentation and the known gold standard and was found to be below 0.8 mm.

Establishing Composition and Structure of Intact Urinary Calculi by X-Ray Coherent Scatter for Clinical Laboratory Investigations

PURPOSEnCurrent urinary stone analysis techniques are limited in their abilities to simultaneously characterize composition and structure. Laboratory techniques such as IRS and x-ray diffractometry require small powdered samples for analysis, rendering composition results dependent on the choice of sample and its preparation. We investigated the application of x-ray CS analysis to identify topographic urinary stone composition ex vivo. CS is essentially a transmission based x-ray diffractometry method that depends on molecular structure and, therefore, can distinguish different compounds. Diagnostic x-ray equipment facilitates the examination of structural arrangements of minerals in intact calculi.nnnMATERIALS AND METHODSnTomographic images of intact calculi CS properties were acquired with a purposely built scanner. Composition is extracted from CS by fitting a library of common pure stone component CS signatures to those of the unknown sample in each image pixel. Two zones per stone were isolated (powdered) for IRS composition analysis for comparison with CS maps at these locations. Each stone was also independently analyzed for bulk composition by IRS analysis.nnnRESULTSnCS composition maps revealed the spatial arrangement of minerals in intact calculi. IRS results showed good agreement with CS in the selected regions of interest. Bulk composition by IRS was noted to miss some important stone components, indicating that the choice of sample may skew composition results.nnnCONCLUSIONSnCS from diagnostic x-rays can be used to identify structure and composition in mixed urinary calculi nondestructively. The tissue specific CS images presented support the development of CS analysis as a means of identifying stone composition characteristics in the laboratory.

Access, Stents, and Urinary Drainage

Ureteral access is necessary in many endourological procedures including ureteroscopy and ureteral stenting. Technologies such as ureteral access sheaths, balloon dilators, and coaxial dilators may be helpful in facilitating ureteral access in difficult cases. This chapter describes a stenting technique that relies on fluoroscopic guidance once the initial guidewire is placed and the cystoscope is removed.

Thermal and histological effects of bipolar and monopolar electrosurgical resection of the prostate in a canine model

Bipolar transurethral resection (TUR) is an alternative to monopolar TUR in the treatment of benign prostatic hyperplasia and offers the major advantage of utilizing 0.9% sodium chloride for irrigation. Claims have been made that bipolar electrosurgery in clinical use causes less thermal damage to adjacent tissues. We sought to assess tissue thermometry and histopathologic thermal effects of a bipolar system in comparison to standard monopolar TUR in an animal model. Eight male beagles were studied. A lower midline incision was used to access the prostate. Fiber-optic thermosensors were placed within the prostate. A midline cystotomy was used to perform antegrade resection of the prostate using a bipolar TUR system (VISTA CTR) with normal saline or a monopolar device using glycine. Resection of a 1cm cavity was performed in each lateral lobe. Animals were sacrificed acutely and the prostates excised for histopathological assessment of thermal damage. In both groups, prostatic temperature rises were transient and fell with increasing distance from the resection site. The greatest temperature increase occurred in the monopolar group (24.2 ± 3.9°C) compared to the bipolar group (6.8 ± 1.8°C, p<0.0001). The depth of thermal damage was greatest in the monopolar group (0.59 ± 0.27mm vs 0.15 ±0.02mm in the bipolar arm, p<0.0001). Bipolar TUR generated significantly less heat and produced less histopathological thermal damage compared to monopolar prostatic resection in a canine model. The clinical benefits of these findings remain to be determined.

Urethral Stents: Review of Technology and Clinical Applications

Urethral stents are a minimally invasive therapy used in the treatment of benign prostatic hyperplasia, urethral stricture, or detrusor sphincter dyssynergia. This chapter reviews the different types of urethral stents, indications for their use, and clinical results. Urethral stents may be positioned in the urethra or prostatic urethra and are classified as temporary or permanent. Temporary stents are further subdivided into biodegradable and nonbiodegradable. This form of therapy is particularly useful in patients who are at high anesthetic risk and are unable to undergo surgical procedures considered to be the gold standard, such as transurethral prostatectomy or open urethroplasty for prostatic enlargement and urethral stricture disease. Urethral stents can provide an effective alternative to transurethral and open procedures in many urological disorders that affect the prostate and urethra.