Advances in Endourology

There were a number of innovative presentations at the 21st World Congress on Endourology and Shockwave Lithotripsy/19th Basic Research Symposium, held September 21–24, 2003, in Montreal. Here, the highlights of the basic research portion of the Congress are reviewed, grouped into the following categories: endoscopic simulators and skill acquisition, metabolic stone disease, shockwave lithotripsy, ureteroscopy, percutaneous surgery, the lower urinary tract, and laparoscopy.

Endoscopic Simulators and Skill Acquisition

Simulators to facilitate endoscopic skill development have recently become available. Ogan and colleagues¹ reported that medical student performance on a virtual ureteroscopy simulator is predictive of outcomes of cadaveric ureteroscopic procedures. These findings are an important step in the validation process of this simulator as an indicator of endoscopic skill level. Knudsen and colleagues² introduced a computer-based virtual reality simulator of percutaneous surgery. The effectiveness of this simulator will need to be assessed in future studies.

A number of presentations provided insight into acquisition of learning skills. Anderson and colleagues³ reported that younger surgeons performed a group of standardized laparoscopic tasks more efficiently than older surgeons when a standard laparoscopic approach was used, whereas there were no age-related performance differences when robotic assistance was utilized. Nakada and colleagues⁴ reported that urologists attending a 2-day, hands-on laparoscopy course in which mentored videotape critique was employed had significant improvement in performance of standardized laparoscopic tasks.

Metabolic Stone Disease

Presentations on metabolic stone disease provided insight into the pathophysiology of stone formation, patient evaluation, and preventive therapy. Using advanced digital and endoscopic equipment, Kuo and colleagues⁵ measured fractional papillary Randall’s plaque coverage and found it to be higher in stone-formers. Urinary calcium excretion directly correlated with plaque coverage, whereas there was an inverse correlation with urinary volume. This same group of investigators performed papillary and renal cortical biopsies in idiopathic calcium oxalate stone-formers at the time of percutaneous nephrolithotomy (PNL).⁶ They found that Randall’s plaques are composed of calcium phosphate and that the initial sight of plaque formation is in the basement membrane of the loop of Henle.

Shah and colleagues⁷ reported that, in healthy adults following a prescribed metabolic diet (20% protein, 30% fat, 50% carbohydrate, 250 mg oxalate, 1000 mg calcium, all adjusted to 2500 kcal), urinary metabolic stabilization was achieved within 48 hours. These results indicate that lead-in times for healthy persons following this metabolic diet can be shortened from the typical 7- to 10-day period used by a number of investigators. Ekeruo and colleagues⁸ analyzed metabolic abnormalities and stone composition in obese persons. They found that uric acid stones were the most prevalent (63%) in this population. Hypercalciuria, low urine volume, gouty diathesis, hyperuricosuria, and hyperoxaluria were the most common metabolic abnormalities, which is reflective of underlying purine gluttony. Johnston and colleagues⁹ reported that ampicillin increased the in vitro solubility of cystine. Further studies are needed to determine whether this agent will be useful in the management of cystinuric patients.

Shockwave Lithotripsy

Methods and technology to improve results of shockwave lithotripsy (SWL) were presented during this session. Pace and colleagues¹⁰ demonstrated in a randomized clinical trial that SWL performed at a rate of 60 shocks per minute resulted in better fragmentation of renal calculi and superior stone-free rates compared with 120 shocks per minute. Young and colleagues¹¹ found that a dual-pulse lithotriptor composed of a Dornier HM3 device with reflector insert and a piezoelectric lithotriptor resulted in improved stone fragmentation with less renal injury in a porcine model. The piezoelectric generator produces a shock wave that is emitted after the electrohydraulic shock wave, resulting in collapse of cavitation bubbles from the initial shock wave at the stone surface and thus in better fragmentation. The inserted reflector attenuates cavitation-induced renal injury.

Ureteroscopy

There is an ongoing debate regarding the optimal therapy for patients with lower pole renal calculi. Kuo and colleagues¹² reported results of a multi-center, randomized, prospective trial comparing SWL and ureteroscopy for the treatment of lower pole renal calculi less than 10 mm in aggregate size: the stone-free rate was superior in subjects who underwent ureteroscopy, and the need for secondary intervention was greater in those who underwent SWL. The same group of investigators reported results of a randomized, prospective study comparing ureteroscopy and PNL for the management of lower pole stones 11 to 25 mm in aggregate size.¹³ The stone-free rate was significantly greater, and morbidity was slightly higher, in the subjects who underwent PNL.

Improvements in flexible ureteroscopic technology were highlighted. Grasso and Johnson¹⁴ presented their experience with a flexible ureteroscope with greater than 300° primary active deflection and noted that it facilitated a number of ureteroscopic procedures. Placement of instruments through the working sheath attenuated deflection, but deflection was still greater than 180°. Lee and colleagues¹⁵ reported on a temperature-activated Nitinol sheath, which can be placed with a laser fiber through the working channel of a flexible ureteroscope. Deflection is limited to a lesser extent when this sheath is used.

Fluid absorption is a potential complication of ureterorenoscopy. Cybulski and colleagues¹⁶ carefully assessed fluid absorption in 16 patients subjected to ureteroscopic procedures. Results showed that a mean of 54 mL of fluid was systemically absorbed (range, 4–137 mL). The amount of fluid absorbed was directly related to the length of the procedure and was estimated to be 1 mL/min.

Percutaneous Surgery

Several innovations for percutaneous renal surgery were presented. Challacombe and colleagues¹⁷ demonstrated that transoceanic telerobotic percutaneous renal access is feasible. Lobik and colleagues¹⁸ evaluated a new-generation orthogonal deflecting flexible cysto/nephroscope with 2 active deflections, which can be activated in different planes perpendicular to each other or in 2 opposite directions, with a total angle of 350°. This may facilitate endoscopy of the renal collecting system, bladder, augmented bladders, neo-bladders, and cutaneous diversions.

The Lower Urinary Tract

Interesting presentations on the lower urinary tract were delivered. DiTrolio and Dubocq¹⁹ reported that pellets containing high concentrations of sodium chloride implanted in rat liver generated tissue necrosis. They propose that transrectal delivery of such pellets to the prostate may prove to be suitable therapy for benign prostatic hyperplasia. Molina and colleagues²⁰ used an argon beam coagulator to ablate the mucosa of ileum used for enterocystoplasty in swine and found that this allowed resurfacing with transitional cell epithelium. This technique may prove to limit mucus-related problems in patients undergoing this procedure.

Laparoscopy

Several novel studies on laparoscopic techniques were presented. Venkatesh and colleagues²¹ reported that viable cells were seen within the staple lines at the ureterovesical junction in swine 6 weeks after nephroureterectomy in which the distal bladder cuff was secured with a stapling device. These findings indicate that this technique may have oncologic ramifications. Uribe and colleagues²² reported that fibrin glue and oxidized regenerated cellulose, materials that may be used during laparoscopic or open partial nephrectomy, assume a semisolid, gelatinous state when mixed with urine in an in vitro system. This “matrix” was shown to still be present at 5 days after incubation; thus, these investigators demonstrated the potential for “iatrogenic stones.”

El-Hakim and colleagues²³ identified several ergonomic risk factors for the development of neuromuscular problems in surgeons after performing laparoscopic procedures. Risk factors include static posture of the head and neck, extreme and frequent upper arm motion, use of finger-grip instruments, increased height of the operating table, improper suturing technique, limited surgical experience, and an instrument angle of greater than 45° relative to the surgeon’s sagittal plane.

Summary

The aforementioned studies, as well as many others presented at this meeting, reflect the progress and innovation that is occurring in the field of endourology. The future utilization of these advancements in knowledge and technology will undoubtedly translate into improved patient care.

Main Points.

• Ogan and colleagues reported that medical student performance on a virtual ureteroscopy simulator is predictive of outcomes of cadaveric ureteroscopic procedures.

• Ekeruo and colleagues analyzed stone composition in obese persons and found uric acid stones to be the most prevalent (63%).

• Results of a randomized clinical trial demonstrated that shockwave lithotripsy (SWL) performed at a rate of 60 shocks per minute resulted in better fragmentation of renal calculi and superior stone-free rates compared with 120 shocks per minute.

• Kuo and colleagues reported results of a multicenter, randomized, prospective trial comparing SWL and ureteroscopy for the treatment of lower pole renal calculi less than 10 mm in aggregate size: the stone-free rate was superior in subjects who underwent ureteroscopy, and the need for secondary intervention was greater in those who underwent SWL.

• The potential of “iatrogenic stones” was demonstrated by Uribe and colleagues, who showed that fibrin glue and oxidized regenerated cellulose, materials that may be used during laparoscopic or open partial nephrectomy, can assume a semisolid state when mixed with urine in an in vitro system.