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Biomedical subjects

Ben H Chew

Publications and source records attributed to Ben H Chew.

15 recordsLinked to original sources
PubMed2006

A randomized, controlled, prospective study validating the acquisition of percutaneous renal collecting system access skills using a computer based hybrid virtual reality surgical simulator: phase I.

PURPOSE: The need to develop new methods of surgical training combined with advances in computing has led to the development of sophisticated virtual reality surgical simulators. The PERC Mentortrade mark is designed to train the user in percutaneous renal collecting system access puncture. We evaluated and established face, content and construct validation of the simulator in this task. MATERIALS AND METHODS: A total of 63 trainees underwent baseline testing on the simulator, consisting of percutaneous renal puncture followed by the introduction of a guidewire into the collecting system. Subjects were then randomized to an intervention arm, in which they underwent 2, 30-minute training sessions on the simulator, and a control arm, in which no further training was given, followed by repeat testing. Performance was assessed using a global rating scale and by virtual reality derived parameters. RESULTS: There were no significant differences between the 2 groups with respect to baseline measures. Subjects who underwent training with the simulator demonstrated significant improvement in objective and subjective parameters compared to their baseline performance and compared to the untrained control group. Spearman rank correlations demonstrated a significant relationship between multiple parameters of the objective and subjective data. CONCLUSIONS: Training on the simulator improves virtual reality skills. It may allow trainees to develop the basic skills necessary to perform percutaneous renal collecting system access. Face and content validity were demonstrated and construct validity was supported by establishing convergent validity.

Computer Simulation↗
PubMed2006

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.

Animals↗
PubMed2006

Establishing composition and structure of intact urinary calculi by x-ray coherent scatter for clinical laboratory investigations.

PURPOSE: Current 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. MATERIALS AND METHODS: Tomographic 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. RESULTS: CS 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. CONCLUSIONS: CS 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.

Crystallography, X-Ray↗
PubMed2006

In-vitro activity of triclosan-eluting ureteral stents against common bacterial uropathogens.

BACKGROUND AND PURPOSE: Ureteral stents are commonly used in urology today, but the biofilms that form on them within hours of placement may harbor bacteria that can result in infection or encrustation. Triclosan is an antimicrobial commonly used in consumer and medical products that inhibits bacterial fatty-acid synthesis. The bactericidal and bacteriostatic effect of a triclosan-eluting ureteral stent was tested against clinical isolates of common bacterial uropathogens in an in-vitro setting. MATERIALS AND METHODS: Triclosan eluted from a drug-loaded ureteral stent was suspended in artificial urine with bacterial pathogens (Escherichia coli C1214, Proteus mirabilis 296, Enterococcus faecalis 1131, Klebsiella pneumoniae 280, Staphylococcus aureus Newman, Pseudomonas aeruginosa AK1) to assess growth, virulence-promoter activity, and bacterial adherence to the stent. Generic stents were utilized as controls. RESULTS: Triclosan inhibited the growth of E. faecalis, K. pneumoniae, S. aureus, and P. mirabilis in a dose-dependent manner. Pseudomonas aeruginosa demonstrated significant resistance. Lower concentrations of triclosan downregulated E. coli virulence-factor promoters of outer membrane protein X and p-fimbriae. Triclosan stents had significantly fewer adherent viable bacteria than control stents. CONCLUSIONS: Triclosan-eluting ureteral stents inhibit the growth of common bacterial uropathogens and thus may reduce the incidence of urinary-tract infections and, potentially, encrustation. This drug-eluting stent provides both mechanical drainage of the upper urinary tract and local antibiosis.

Anti-Infective Agents, Local↗
PubMed2006

Minimizing symptoms in patients with ureteric stents.

PURPOSE OF REVIEW: The current approaches for minimizing symptoms in patients with ureteric stents were reviewed utilizing a literature search on Pubmed using the keywords stent, symptom, and ureter. RECENT FINDINGS: Ureteral stents are widely used in urological procedures for maintaining upper urinary tract drainage to relieve obstruction, pain, or infection. Indwelling stents, however, are associated with significant morbidity such as infection, encrustation, hematuria, and bothersome symptoms. Minimizing these issues has become paramount in the design of new ureteral stents. This article will review current and novel ways to minimize stent-related morbidity. SUMMARY: Currently, there is no ideal stent that relieves obstruction, is resistant to infection and encrustation, and is comfortable for patients. Advances in biomaterials and design will result in a more biocompatible stent that also has patient comfort in mind.

Humans↗
PubMed2006

New developments in ureteral stent design, materials and coatings.

Ureteral stents are used in a variety of urological diseases and procedures. The majority of patients with indwelling ureteral stents experience bothersome symptoms and are at increased risk for urinary tract infection. Stent encrustation and the associated complications can also result in significant patient morbidity. The development of new stent designs using novel biomaterials, stent coatings and drug-eluting technologies are being applied to reduce the disadvantageous features of ureteral stents.

Coated Materials, Biocompatible↗
PubMed2005

Design of functional simulation of renal cancer in virtual reality environments.

OBJECTIVES: The preoperative planning of partial nephrectomy can be facilitated by the ability to view the tumor and surrounding tissue in three-dimensional (3D) virtual reality (VR). A technique to convert Digital Imaging and Communications in Medicine computed tomography scan data into a fully 3D VR environment was developed. The model can be transferred to a personal computer, allowing the surgeon to view the 3D model in the operating room. METHODS: Computed tomography data from a patient with multifocal renal masses was converted into a 3D polygonal mesh using Amira running on a desktop personal computer with Windows XP Professional. A Silicon Graphics Monster Onyx2 running the Linux operating system was used to view the 3D stereo model in the VR environments: either the CAVE or a specialized desk called the Immersadesk. An application to view and interact with the model on a desktop personal computer was written in C++. RESULTS: A 3D model of the kidney, the multiple tumors, and the associated systems was created. The model could be viewed and manipulated in a true VR environment and on a desktop personal computer. CONCLUSIONS: This project completed two major goals. First, a 3D model of a kidney containing multiple masses was created and viewed in a VR environment. Second, an interface to display the model on a desktop personal computer in the operating room was created. This is the first step in bringing VR technology to the operating room to assist the surgeon directly.

Aged↗
PubMed2005

Performance and safety of holmium: YAG laser optical fibers.

BACKGROUND AND PURPOSE: Lower-pole ureteronephroscopy requires transmission of holmium:YAG energy along a deflected fiber. Current ureteroscopes are capable of high degrees of deflection, which may stress laser fibers beyond safe limits during lower-pole use. We hypothesized that optical fiber and safety measures differ among manufacturers. MATERIALS AND METHODS: Small (200-273-microm) and medium-diameter (300-400-microm) Ho:YAG fibers were tested in a straight and 180 degrees bent configuration. Energy transmission was measured by an energy detector. Fiber durability was assessed by firing the laser in sequentially tighter bending diameters. The fibers were bent to 180 degrees with a diameter of 6 cm and run at 200- to 4000-mJ pulse energy to determine the minimum energy required to fracture the fiber. The bending diameter was decreased by 1-cm increments and testing repeated until a bending diameter of 1 cm was reached. The maximum deflection of the ACMI DUR-8E ureteroscope with each fiber in the working channel was recorded. The flow rate through the working channel of the DUR-8E was measured for each fiber. RESULTS: The mean energy transmission differed among fibers (P < 0.001). The Lumenis SL 200 and the InnovaQuartz 400 were the best small and medium-diameter fibers, respectively, in resisting thermal breakdown (P < 0.01). The Dornier Lightguide Super 200 fractured repeatedly at a bend diameter of 2 cm and with the lowest energy (200 mJ). The other small fibers fractured only at a bend diameter of 1 cm. The Sharplan 200 and InnovaQuartz Sureflex 273T were the most flexible fibers, the Lumenis SL 365 the least. The flow rate was inversely proportional to four times the power of the diameter of the fiber. CONCLUSIONS: Optical performance and safety differ among fibers. Fibers transmit various amounts of energy to their cladding when bent. During lower-pole nephroscopy with the fiber deflected, there is a risk of fiber fracture from thermal breakdown and laser-energy transmission to the endoscope. Some available laser fibers carry a risk of ureteroscope damage.

Aluminum↗
PubMed2005

A retroperitoneal gastrointestinal schwannoma presenting as a perinephric mass.

There are less than 100 cases of retroperitoneal schwannoma reported in the world literature. These are differentiated from gastrointestinal schwannomas found in the gastrointestinal tract. A case of a rare retroperitoneal gastrointestinal schwannoma presenting as a perinephric tumor is described. Treatment of such masses is local excision and final diagnosis is from histopathology.

Female↗
PubMed2004

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 urologist's 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.

Biocompatible Materials↗
PubMed2004

The use of stents in contemporary urology.

PURPOSE OF REVIEW: Ureteral stents are a mainstay of today's 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.

Biocompatible Materials↗
PubMed2002

Munchausen syndrome presenting as gross hematuria in two women.

Munchausen syndrome is an uncommon disorder in which patients present with fictitious disorders and a self-destructive urge to undergo invasive procedures. We present 2 cases of nurses who presented with recurrent urinary tract infections, flank pain, and gross hematuria. One patient had such severe hematuria as to require transfusions of more than 1000 U of packed red cells during a 30-year period. Both patients underwent extensive investigations--all of which were normal. One patient even underwent nephrectomy, which showed normal pathologic findings. Both were found to be phlebotomizing themselves and infusing blood into their bladders.

Adult↗
PubMedDate not supplied

Combined transurethral and laparoscopic partial cystectomy and robot-assisted bladder repair for the treatment of bladder endometrioma.

A 40-year-old nulliparous woman with a 7-year history of progressive abdominal discomfort and lower urinary tract symptoms was diagnosed with a deeply infiltrating 4-cm bladder endometrioma. After failing conservative therapy, she was treated with simultaneous transurethral and laparoscopic partial cystectomy and robot-assisted bladder reconstruction. She remained symptom free at last follow-up.

Adult↗
PubMedDate not supplied

Percutaneous management of upper-tract transitional cell carcinoma.

The gold standard treatment for supravesical urothelial carcinoma has been open radical nephroureterectomy based on the premise that this cancer is a field defect. However, nephroureterectomy is an extensive procedure that may not be tolerated by all patients. Percutaneous and ureteroscopic approaches have been utilized in an attempt to avoid the potential morbidity associated with traditional open surgery. This review provides an update on percutaneous management of upper-tract urothelial transitional-cell cancer based on a review of the pertinent literature.

BCG Vaccine↗