PubMed Health⌕ Search

Biomedical subjects

J D Denstedt

Publications and source records attributed to J D Denstedt.

At least 19 recordsLinked to original sources
PubMed2005

Ureteroscopy for pediatric urolithiasis: an evolving first-line therapy.

OBJECTIVES: To present in a retrospective report a contemporary series of patients aged 14 years and younger who were treated for stones with ureteroscopy at our institution from 1991 to 2002. With the improvement and miniaturization of ureteroscopes and ancillary instruments, the endoscopic treatment of renal and ureteral calculi in children has become more feasible. METHODS: A retrospective chart review was performed of 23 patients aged 14 years and younger who had undergone ureteroscopy for the treatment of ureteral or renal calculi at our institution. RESULTS: A total of 27 stones were treated in 23 patients. Of the 27 stones, 18 were in the distal ureter, 5 in the mid ureter, 2 in the proximal ureter, and 2 in the renal pelvis. Ureteral dilation was performed in 4 (17.4%) of the 23 patients. The lithotripsy modalities used were holmium:yttrium-aluminum-garnet laser in 16 (69.6%), electrohydraulic lithotripsy in 3 (13%), a combination of holmium laser and electrohydraulic lithotripsy in 2 (8.7%), and basket extraction alone in 2 (8.7%) of 23 patients. Ureteral stents were placed in 21 (91.3%) of 23 patients. The average operative time was 46.9 minutes (range 15 to 92). In 21 (91.3%) of 23 patients, postoperative imaging was available and revealed that 20 (95.2%) of the 21 patients were rendered stone free. Two patients were lost to follow-up. No intraoperative complications occurred. One patient was treated postoperatively with intravenous antibiotics for transient fever. CONCLUSIONS: Ureteroscopy is safe and effective in the management of ureteral and renal calculi in children. In our institution, it has emerged as a valid first-line therapy for the treatment of pediatric urolithiasis.

Adolescent↗
PubMed2004

Results of shockwave lithotripsy for pediatric urolithiasis.

BACKGROUND AND PURPOSE: Shockwave lithotripsy (SWL) is widely practiced in the management of pediatric urolithiasis. However, the efficacy, need for ancillary procedures, and treatment-related complications are not as clearly defined as in the adult population. We reviewed the outcomes of SWL in the pediatric population at our lithotripsy unit. PATIENTS AND METHODS: A retrospective review of all patients </=16 years of age treated with SWL between January 1991 and June 2002 was undertaken. One hundred patients with 115 stones underwent 131 SWL procedures (115 first treatments, 16 retreatments). The mean age was 10.7 years (range 10 months-16 years). Stone locations were as follows: caliceal 42.6%, renal pelvic 27%, and ureteral (30.4%). The mean stone size was 7.8 mm (range 2-23 mm). Risk factors for stone formation, the need for secondary therapies, and treatment-related complications were noted. The stone-free rate for a single-session SWL procedure, defined as complete absence of stone fragments on plain film, intravenous urography, or renal ultrasonography, was calculated based on 3-month follow-up. The efficiency quotient (EQ) was also calculated. RESULTS: Risk factors were identified in 31 children (27.0%), including metabolic and anatomic abnormalities. Patients with a risk factor were less likely to be stone free after one SWL session than those without risk factors (31.7% v 64.7%; P < 0.001). General (74.8%), neurolept (24.4%), and epidural (0.8%) anesthesia were utilized. Ureteral stents were placed in 25% of treatments. There were no intraoperative complications. Minor complications were seen in 4.6% of patients. Ancillary procedures were required in 10 patients. Following initial SWL treatment, 60.2% of patients were stone free. The retreatment rate was 13.9%. Following a second treatment, the stone-free rate increased to 68%. The EQ was 54.3. CONCLUSION: Employing a strict definition of treatment success, single-session SWL in our series offers moderate efficacy in the pediatric population. Patients who have a large stone or risk factor such as an anatomic abnormality are less likely to become stone free and might better undergo an endourologic procedure.

Adolescent↗
PubMed2001

Lower pole I: a prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis-initial results.

PURPOSE: The efficacy of shock wave lithotripsy and percutaneous stone removal for the treatment of symptomatic lower pole renal calculi was determined. MATERIALS AND METHODS: A prospective randomized, multicenter clinical trial was performed comparing shock wave lithotripsy and percutaneous stone removal for symptomatic lower pole only renal calculi 30 mm. or less. RESULTS: Of 128 patients enrolled in the study 60 with a mean stone size of 14.43 mm. were randomized to percutaneous stone removal (58 treated, 2 awaiting treatment) and 68 with a mean stone size of 14.03 mm. were randomized to shock wave lithotripsy (64 treated, 4 awaiting treatment). Followup at 3 months was available for 88% of treated patients. The 3-month postoperative stone-free rates overall were 95% for percutaneous removal versus 37% lithotripsy (p <0.001). Shock wave lithotripsy results varied inversely with stone burden while percutaneous stone-free rates were independent of stone burden. Stone clearance from the lower pole following shock wave lithotripsy was particularly problematic for calculi greater than 10 mm. in diameter with only 7 of 33 (21%) patients becoming stone-free. Re-treatment was necessary in 10 (16%) lithotripsy and 5 (9%) percutaneous cases. There were 9 treatment failures in the lithotripsy group and none in the percutaneous group. Ancillary treatment was necessary in 13% of lithotripsy and 2% percutaneous cases. Morbidity was low overall and did not differ significantly between the groups (percutaneous stone removal 22%, shock wave lithotripsy 11%, p =0.087). In the shock wave lithotripsy group there was no difference in lower pole anatomical measurements between kidneys in which complete stone clearance did or did not occur. CONCLUSIONS: Stone clearance from the lower pole following shock wave lithotripsy is poor, especially for stones greater than 10 mm. in diameter. Calculi greater than 10 mm. in diameter are better managed initially with percutaneous removal due to its high degree of efficacy and acceptably low morbidity.

Humans↗
PubMed2001

Serum biochemical changes after laparoscopy may be indicators of bladder injury.

We evaluated the serum renal biochemical profile as an indicator of unrecognized laparoscopic bladder injury in four women. The patients were seen 24 to 56 hours postoperatively with elevated serum creatinine and urea levels, and electrolyte changes compatible with acute renal dysfunction. The mechanism responsible for these biochemical changes appears to be extravasation and reabsorption of urine. Biochemical values returned to normal within 24 hours after bladder repair.

Adult↗
PubMed2001

Stray radiofrequency current as a cause of urethral strictures after transurethral resection of the prostate.

PURPOSE: This study was designed to define the pattern and significance of stray currents induced by two electrosurgical generators (ESGs) in relation to urethral strictures forming after transurethral resection of the prostate (TURP). MATERIALS AND METHODS: A 24F resectoscope irrigated with glycine was activated at various power outputs in different modes, with intact loops and loops with faulty insulation, simulating TURP. The Valleylab and ERBE ESGs were compared for inducing capacitance. An ESG analyzer simulated tissue impedance and recorded the stray currents induced along the resectoscope sheath. A fresh pig liver was used for assessment of tissue damage caused by the currents. RESULTS: In the cutting mode, the ERBE ESG produced a mean stray current of 70 mA with an intact loop and 144 mA with a loop having faulty insulation. The Valleylab ESG produced 150 mA and 161 mA, respectively. In the coagulation mode, the ERBE ESG produced an average leakage current of 35 mA and, with a loop with faulty insulation, 40 mA. The Valleylab ESG produced 148 mA and 151 mA, respectively. CONCLUSIONS: Electrical injury may represent a significant cause of urethral stricture after transurethral electrosurgery. The critical power density of 7.5 W/cm2 (which is likely to cause a urethral burn) may be reached, especially with the use of loops with faulty insulation or nonconductive lubricating gel. The ERBE ESG produced significantly less capacitance, decreasing the risk of urethral electrical burn. Conductive gel prevents dangerous current concentration.

Electric Injuries↗
PubMed2001

A prospective randomized controlled trial comparing nonstented versus stented ureteroscopic lithotripsy.

PURPOSE: A prospective randomized controlled trial was performed to determine whether stents may be eliminated after uncomplicated ureteroscopic lithotripsy for ureteral stones. MATERIALS AND METHODS: A total of 58 patients underwent uncomplicated ureteroscopic intracorporeal lithotripsy. After stone fragmentation patients were randomized to a nonstented (29) or a stented (29) treatment group. Intracorporeal lithotripsy was performed with the holmium laser in 57 cases and by electrohydraulic lithotripsy in 1 without balloon dilation or the extraction of stone fragments. Patients were followed 1, 6 and 12 weeks postoperatively. In stented cases the stent was removed at 1 week. Outcome measures included postoperative symptoms assessed with a visual analog scale, postoperative analgesic requirements, complications and the stone-free rate. RESULTS: At 1 week the symptoms of flank pain, abdominal pain, dysuria and frequency were significantly greater in the stented group (p <0.005). There were no differences in symptoms in the groups at subsequent followup visits. There was no difference in treatment groups in terms of the amount of analgesic required in the recovery room or during 1 week after ureteroscopy. Similarly there was no difference in the number of patients requiring antiemetics. One patient in the stented group required hospitalization for genitourinary sepsis and 1 patient in the nonstented group visited the emergency room for postoperative vomiting. The stone-free rate was 100% in each group. CONCLUSIONS: These results demonstrate that after ureteroscopic intracorporeal lithotripsy with the holmium laser patients with a stent have significantly greater irritative and painful symptoms than those without a stent in the early postoperative period. There was no difference in nonstented and stented ureteroscopy with respect to complications or stone-free status. Therefore, we believe that routine stenting after ureteroscopic intracorporeal lithotripsy with the holmium laser is not required as long as the procedure is uncomplicated and performed without balloon dilation of the ureteral orifice.

Adult↗
PubMed2000

Advances in ureteral stent technology.

This review focuses on technological advances and relevant research related to ureteral stents. The importance of physical and chemical biomaterial type, biocompatibility, material coatings such as hydrogels, and infection related to indwelling ureteral stents are discussed. Recent in vitro and in vivo research has focused on materials that will reduce encrustation and bacterial biofilm formation. The adsorption of antimicrobials onto devices holds promise of reducing infection rates, but multidrug resistant bacteria, short leaching times and adverse side effects make it essential that alternative strategies be investigated. Just so, encrustation limits the long-term use of urinary materials, and a better understanding of factors involved in encrustation are needed to reduce the problem.

Biocompatible Materials↗
PubMed2000

Intracorporeal lithotripsy. Update on technology.

The number and variety of devices currently available for endoscopic lithotripsy reflect the reality that no single device is ideal in all situations. Although the search for the universal lithotriptor continues, the urologist must consider several factors if faced with the decision of which device to purchase. Perhaps foremost among these factors is the clinical situation with which one commonly deals. For example, although the smaller, flexible probes such as EHL or laser demonstrate considerable utility if used ureteroscopically, the larger stone burden associated with today's percutaneous nephrolithotripsy population often is treated more efficiently with one of the mechanical devices employing a larger, rigid probe, such as ultrasound or the Lithoclast. Similarly, the type and size of endoscopic equipment at one's disposal have a significant impact on which device to purchase or use. There are physical constraints affecting which device may or may not be used, rigid versus flexible endoscope, working channel caliber, and offset versus end-on-port. The skill and experience of the surgeon is also a factor of obvious importance, particularly if one is using a modality with a relatively narrow margin of safety such as EHL. Likewise, the training and experience of nursing personnel is a factor, especially regarding the use of lasers, which require certified personnel who are well versed in laser safety. Finally, in today's environment one must carefully evaluate cost in terms of not only initial capital outlay but also ongoing charges for disposable and maintenance items. Thus, the decision of which device to purchase is complex and requires careful evaluation of all of the previously noted variables. Likewise, if one is fortunate enough to have more than one device available, the decision of which lithotriptor to employ requires a similar decision based on sound surgical judgment.

Equipment Design↗
PubMed2000

Electrical burn of urethra as cause of stricture after transurethral resection.

BACKGROUND AND PURPOSE: One of the most common complications of transurethral resection is urethral stricture. The exact etiology is still controversial. Postulated pathophysiology ranges from mechanical trauma to the urethra during the resection to inflammatory reaction secondary to local anesthesia. We propose electrical burn to the urethra as a contributory factor in some cases. MATERIALS AND METHODS: Electrical events during transurethral resection were simulated in vitro. The distribution of current was measured at the loop/rollerball and in the outer metal sheath. Both an intact loop/rollerball and loop/rollerball with faulty insulation were tested. Various power outputs simulating coagulation, cutting, and vaporization were used. Data were recorded both in settings where the outer metal sheath was and was not smeared with nonconductive lubricating gel. RESULTS: Approximately 20% of the total current output was shunted to the metal sheath when an intact loop/rollerball was used. One hundred percent of the current was short-circuited to the sheath when a loop/rollerball with faulty insulation was retracted into the sheath. Little current was detectable in the nonconductive lubricating gel. We then calculated the length of time required, in various settings, to reach tissue temperature of 45 degrees C, when protein denaturation starts. The higher the power output and the smaller the contacting surface area, the more likely it is for urethral burns to occur. CONCLUSION: Our in vitro experiment showed that urethral burns secondary to stray current in the resectoscope sheath are unlikely when an intact loop is used. However, urethral burns can occur when a loop/rollerball with faulty insulation is used, especially in combination with nonconductive gel that is dispersed unevenly within the urethra.

Animals↗
PubMed2000

Encrustation of biomaterials in the urinary tract.

The present review focuses on technological advances and relevant research related to encrustation of biomaterials in the urinary tract. The importance of physical and chemical biomaterial type, biocompatibility, material coatings such as hydrogels, and infection related to alloplastic materials used in urological practice are discussed. Recent in-vitro and in-vivo research has focused on materials that will reduce encrustation and bacterial biofilm formation, complications that limit the long-term use of urinary materials. Coordinating scientific resources in a multidisciplinary manner for a better understanding of factors that are involved in encrustation and biofilm formation will offer the potential to modify or resolve the problem of encrustation of foreign materials in the urinary tract.

Biocompatible Materials↗
PubMed1999

Holmium:YAG lithotripsy in children.

PURPOSE: We determined the safety and efficacy of holmium:YAG lithotripsy in children. MATERIALS AND METHODS: We retrospectively reviewed the records of all holmium:YAG lithotripsy done in patients 17 years old or younger. Demographic, preoperative, intraoperative and postoperative data were collected. RESULTS: A total of 9 boys and 10 girls (26 stones) with a mean age of 11 years (range 1 to 17) were treated with holmium:YAG lithotripsy, which was chosen as initial therapy in 10 (53%). Retrograde ureteroscopy was performed in 15 patients to treat 13 ureteral and 6 renal calculi, and percutaneous nephrolithotripsy was done in 4 to treat 3 ureteral and 4 renal calculi. A complete stone-free outcome after 1 procedure was achieved in 16 children (84%) and 3 patients were rendered stone-free after 2 procedures. No patient had an intraoperative injury. Followup ranged from 0.5 to 12 months (mean 3). Followup imaging has shown no evidence of stricture or hydronephrosis. CONCLUSIONS: Holmium:YAG lithotripsy is safe and effective in children. It is a reasonable option for failed shock wave lithotripsy, or in children with a known durile stone composition or contraindications to shock wave lithotripsy.

Adolescent↗
PubMed1999

Holmium: YAG laser resection of the prostate.

The holmium laser is a relatively new multipurpose medical laser that recently became available for use in urology. There has been considerable interest in this device, as it seems to combine the cutting properties of the carbon dioxide laser with the coagulating properties of the neodymium:YAG laser, making it particularly appealing for many surgical applications. The last decade has seen enthusiasm for the use of laser energy for the treatment of benign prostatic hyperplasia. In this article, we review the technique of Ho:YAG laser resection of the prostate, including the essential equipment and perioperative patient care.

Holmium↗
PubMed1999

Identifying stone composition using infrared analysis of filtered urine after ureteroscopic lithotripsy.

BACKGROUND AND PURPOSE: With the development of small-caliber ureteroscopes and lithotripsy devices, it is now possible to perform intracorporeal stone fragmentation without dilatation of the ureteral orifice. Ureteral stones are typically fragmented into small particles that can be difficult to retrieve for stone analysis. Infrared spectroscopy (IRS) of the precipitate from urine after intracorporeal lithotripsy represents a method for obtaining stone analysis. PATIENTS AND METHODS: A total of 69 patients underwent ureteroscopic lithotripsy with the holmium laser or the electrohydraulic probe for stones in the ureter (N = 65) or kidney (N = 4). Each patient's bladder was then drained and the urine filtered. The resulting precipitate was analyzed using IRS. RESULTS: The amount of material for analysis was < or =1 mg in 56 patients (82%). Stone composition was positively identified in 44 patients (64%). Material suitable for analysis was recovered from 73% of patients when the bladder was drained with a cystoscope sheath compared with 43% when a urethral catheter was used (P = 0.03). There was no significant difference in pretreatment stone size in the patients who had a positive v a negative result (11.7 mm v 10.9 mm; P = 0.06). Similarly, the stone location was not significantly related to the likelihood of positive analysis (P = 0.29). CONCLUSION: Straining the urine after ureteroscopic intracorporeal lithotripsy and analyzing the precipitate with IRS is able to identify stone composition in the majority of patients. This method is especially useful in the setting of holmium laser lithotripsy, in which the majority of the stone is converted to spontaneously passable particles.

Female↗
PubMed1999

Percutaneous suprapubic cystolithotripsy for treatment of large bladder calculi.

BACKGROUND AND PURPOSE: The treatment options available for managing bladder calculi include transurethral cystolithotripsy, open cystolithotomy, and shockwave lithotripsy. For larger calculi, transurethral treatment can be time consuming, and the manipulation has the potential to cause urethral injury. Percutaneous suprapubic cystolithotripsy represents another treatment option for bladder calculi which is effective and minimally invasive. PATIENTS AND METHODS: Fifteen patients had bladder calculi treated with percutaneous cystolithotripsy over a 3-year period. The mean stone size was 39 mm (range 10-64 mm). Stones were single in seven patients and multiple in eight patients. The indications for cystolithotripsy were stone size >3 cm, multiple stones >1 cm, and inability to perform transurethral cystolithotripsy because of patient anatomy. Percutaneous suprapubic cystolithotripsy was done through either a 30F or a 36F cystotomy tract. Fragmentation and removal was performed with a 26F rigid nephroscope and the pneumatic Swiss Lithoclast. Suprapubic and urethral catheters were placed postoperatively in all patients. RESULTS: Each patient was cleared of the stone burden with a single procedure, and there were no major complications. The mean duration of suprapubic catheterization was 2.6 (range 1-5) days. CONCLUSION: Percutaneous suprapubic cystolithotripsy is an effective and safe technique for treating large bladder calculi. It is minimally invasive, avoids urethral injury, and, in combination with the pneumatic Swiss Lithoclast, can be used to fragment and remove large and hard bladder calculi.

Aged↗
PubMed1998

Secondary ureteroscopy: results and management strategy at a referral center.

PURPOSE: In an era when extracorporeal shock wave lithotripsy occupies a dominant place in the treatment of urolithiasis ureteroscopy retains an important role in certain circumstances. While often a definitive procedure, ureteroscopy can be associated with potential risks and complications. The treatment of patients who have undergone a failed attempt at ureteroscopic stone retrieval or have a complication may be complex. As a tertiary care stone referral center we review our experience with performing salvage ureteroscopy following a previous unsuccessful attempt at endoscopic stone removal. MATERIALS AND METHODS: Between May 1990 and February 1996, 79 patients were referred following an unsuccessful attempt at retrograde endoscopic or basket manipulation for ureteral calculi. A retrospective review of the outcomes of these patients was conducted. Of the patients 11 presented with associated complications, which included ureteral perforation (4), intramural false passage (1) and fever or sepsis (6). Complications were managed by early establishment of urinary tract drainage by stenting or nephrostomy. Among patients without complications elective salvage ureteroscopy was performed. RESULTS: Ureteroscopy was used in 79 patients with a successful outcome (stone-free) in 75 (95%). Followup imaging with renal ultrasound or excretory urography at least 3 months after secondary ureteroscopy was available in 65 patients and showed no evidence of hydronephrosis or delayed stricture formation. CONCLUSIONS: Treating the patient who undergoes a failed attempt at ureteroscopy may be problematic and requires access to a wide array of endourological equipment. Each subsequent treatment should be individualized with consideration given to stone size, location and general health. In the presence of a ureteral injury establishment of early urinary tract drainage is essential. Following stabilization, secondary ureteroscopy can be performed yielding high stone-free rates with minimal complications.

Adolescent↗
PubMed1998

The holmium laser in urology.

OBJECTIVE: To review the physics related to the holmium laser, its laser-tissue interactions, and its application to the treatment of urological diseases. SUMMARY AND BACKGROUND DATA: The holmium: YAG laser is a solid-state, pulsed laser that emits light at 2100 nm. It combines the qualities of the carbon dioxide and neodymium:YAG lasers providing both tissue cutting and coagulation in a single device. Since the holmium wavelength can be transmitted down optical fibers, it is especially suited for endoscopic surgery. METHODS: The authors provide a review of the literature as it relates to the holmium laser and its application to urology. RESULTS: The holmium wavelength is strongly absorbed by water. Tissue ablation occurs superficially, providing for precise incision with a thermal injury zone ranging from 0.5 to 1.0 mm. This level of coagulation is sufficient for adequate hemostasis. The most common urologic applications of the holmium laser that have been reported include incision of urethral and ureteral strictures; ablation of superficial transitional cell carcinoma; bladder neck incision and prostate resection; and lithotripsy of urinary calculi. CONCLUSIONS: The holmium: YAG laser is a multi-purpose, multi-specialty surgical laser. It has been shown to be safe and effective for multiple soft tissue applications and stone fragmentation. Its utilization in urology is anticipated to increase with time as a result of these features.

Carbon Dioxide↗
PubMed1998

Bacterial biofilm formation, encrustation, and antibiotic adsorption to ureteral stents indwelling in humans.

Encrustation and urinary tract infection are problematic complications of ureteral stent usage. The objective of our first study was to use surface science techniques to examine three ureteral stent types for encrustation, biofilm formation, and antibiotic adsorption after use in patients. Black Beauty (N = 16), LSe (N = 16), and SofFlex (N = 32) ureteral stents were recovered from patients who had received trimethoprim or ciprofloxacin while the stent was indwelling. These stents were examined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX) for the presence and composition of encrustation or biofilm. Conditioning films and encrustations were found on all stents. Encrustation elements (Ca, Mg, P) were identified on 11 of 16 Black Beauty (69%), 7 of 16 LSe (44%), and 12 of 32 SofFlex (38%) stents. The stent type, duration of insertion, and age or sex of the patient did not correlate significantly with the amount of encrustation. Bacterial biofilms were found on 1 of 7 Black Beauty stents (14%) and 7 of 32 SofFlex stents (22%). In a second study, an additional 28 patients with SofFlex stents were treated with ciprofloxacin (N = 16) or ofloxacin (N = 12). Their stents were subjected to high-performance liquid chromatography to determine if oral antibiotic therapy can lead to drug adsorption to the stent. Analysis showed that both ciprofloxacin and ofloxacin adsorbed to the stent surfaces. The mean concentrations of the two antibiotics within the conditioning film of the stents were 0.99 microg/mL and 0.34 microg/mL, respectively. These surface science techniques provide a comprehensive method of evaluating ureteral stents and other prosthetic devices in vivo.

Administration, Oral↗