In vitro analysis of stone fragmentation ability of the FREDDY laser.

Background And Purpose: The Frequency-Doubled Double-Pulse Nd:Yag) (FREDDY) laser (World of Medicine, Berlin Germany) is a short-pulsed, double-frequency solid-state laser with wavelengths of 532 and 1064 nm. This low-power, low-cost laser was developed for intracorporeal lithotripsy. We designed an experimental set-up to test its fragmentation efficiency at different energy and frequency settings.

Percutaneous management of calculi within horseshoe kidneys.

Purpose: Percutaneous treatment of patients with calculi in a horseshoe kidney can be challenging due to the altered anatomical relationship in the retroperitoneum. Therefore, we performed a multi-institutional review to assess the safety and efficacy of this minimally invasive technique.

Materials And Methods: Of 37 patients identified with calculi in a horseshoe kidney at 3 institutions 24 (65%) underwent percutaneous nephrolithotripsy as primary treatment.

Medical management of stone disease.

Purpose Of Review: Dietary manipulation still remains one of the most important strategies for therapy. A growing body of evidence, however, suggests that severe calcium restriction is inappropriate in patients with recurrent nephrolithiasis. Dietary recommendations based on recent evidence and the role of bacteria in the pathogenesis of calcium nephrolithiasis are discussed.

Use of a temporary ureteral drainage stent after uncomplicated ureteroscopy: results from a phase II clinical trial.

Purpose: An indwelling ureteral stent is commonly placed for 48 hours after uncomplicated ureteroscopy to maintain drainage and prevent postoperative complications. A propriety temporary ureteral drainage stent (TUDS, Boston Scientific/Microvasive, Natick, Massachusetts) was developed to satisfy this goal with the added advantages of biodegradability and spontaneous passage. We evaluated TUDS performance in a patient population.

Biochemical profile of stone-forming patients with diabetes mellitus.

Objectives: To test the hypothesis that stone-forming patients with type II diabetes (DM-II) have a high prevalence of uric acid (UA) stones and present with some of the biochemical features of gouty diathesis (GD).

Methods: The demographic and initial biochemical data from 59 stone-forming patients with DM-II (serum glucose greater than 126 mg/dL, no insulin therapy, older than 35 years of age) from Dallas, Texas and Durham, North Carolina were retrieved and compared with data from 58 patients with GD and 116 with hyperuricosuric calcium oxalate urolithiasis (HUCU) without DM.

Results: UA stones were detected in 33.

Assessment of stricture formation with the ureteral access sheath.

Objectives: To analyze the long-term incidence of ureteral stricture formation in a series of patients in whom a new-generation ureteral access sheath was used. A new generation of ureteral access sheaths has been developed to facilitate ureteroscopic procedures. However, some have questioned their safety and whether the device might cause significant ureteral trauma.

Shock wave lithotripsy causes ipsilateral renal injury remote from the focal point: the role of regional vasoconstriction.

Purpose: Shock wave lithotripsy induced renal damage can occur as a result of multiple mechanisms, including small vessel injury and free radical production. Previous studies have demonstrated that shock wave lithotripsy exerts a regional change in renal hemodynamics, resulting in a global reduction in the glomerular filtration rate and renal plasma blood flow. We determined if biochemical evidence of cellular damage could be identified in ipsilateral locations remote from the shock wave site or in the contralateral kidney, suggesting regional or systemic alterations in renal function.

Clinical efficacy of a combination pneumatic and ultrasonic lithotrite.

Purpose: A new combination pneumatic/ultrasonic intracorporeal lithotriptor has been developed for percutaneous applications. It combines the stone clearing efficiency of an ultrasonic device with the fragmentation strength of a pneumatic probe into a single handpiece. We present our early clinical experience with this device in a prospective, randomized comparison a combination pneumatic/ultrasound lithotrite and standard ultrasonic lithotripsy.

Ureteral access sheath facilitates inspection of incision of ureteropelvic junction.

Purpose: The Acucise (Applied Medical, Rancho Santa Margarita, California) electrocautery balloon is a highly successful device used in managing congenital and secondary ureteropelvic junction obstruction. Correct orientation of the cutting wire is essential during insertion of the Acucise catheter to avoid injury to crossing vessels. Moreover, confirmation of the lateral ureteropelvic junction incision is typically verified by fluoroscopic identification of extravasated contrast material.

Durability of the medical management of cystinuria.

Purpose: Cystinuria is an autosomal recessive disorder of dibasic amino acid transport in the kidney that leads to an abundance of cystine in the urine. This molecule is poorly soluble in urine and it is prone to crystallization and stone formation at concentrations above 300 mg./l.

Surgical management of urolithiasis.

The surgical management of urinary calculus disease has changed dramatically in the past two decades. Minimally invasive options have made open stone surgery nearly obsolete. The development of shock wave lithotripsy, percutaneous nephrostolithotomy techniques and intracorporeal lithotripsy devices has conferred unprecedented management tools for upper tract stones.

Long-term combined treatment with thiazide and potassium citrate in nephrolithiasis does not lead to hypokalemia or hypochloremic metabolic alkalosis.

Background: Potassium citrate is commonly used in combination with a thiazide diuretic in the medical management of recurrent hypercalciuric nephrolithiasis. However, concerns have been raised that administration of this nonchloride potassium alkali with a kaliuretic and natriuretic agent such as thiazide may not be efficacious in correcting or preventing hypokalemia, and may produce hypochloremic metabolic alkalosis. This retrospective analysis was conducted to determine if these two potential complications are encountered in patients on long-term potassium citrate and thiazide therapy.

Laser Doppler flowmetric determination of ureteral blood flow after ureteral access sheath placement.

Background And Purpose: The ureteral access sheath has positively impacted ureteroscopy by decreasing operative times and increasing success rates. However, as previous studies have suggested that large-caliber endoscopes may cause ureteral ischemia, concern has been raised about the impact of access sheath insertion on ureteral blood flow. We sought to determine whether the access sheath compromises ureteral blood supply and, if so, causes ischemic damage to the ureter during ureteroscopic procedures.

Endoscopic management of symptomatic caliceal diverticula: a retrospective comparison of percutaneous nephrolithotripsy and ureteroscopy.

Background And Purpose: A myriad of minimally invasive options exist for managing symptomatic caliceal diverticula, including shockwave lithotripsy, percutaneous surgery, retrograde ureteroscopy, and laparoscopy. Yet no direct comparisons have been made in the literature of the relative treatment efficacy of ureteroscopy (URS) and percutaneous nephrolithotripsy (PNL). A retrospective review of our patients was performed to determine the most appropriate endoscopic management option for patients with symptomatic caliceal diverticula.

Techniques to maximize flexible ureteroscope longevity.

Objectives: To assess methods to improve the longevity and durability of flexible ureteroscopes by using the ureteral access sheath, 200-microm holmium laser fiber, and nitinol baskets or graspers during routine ureteroscopic procedures. Despite adequate advances in fiberoptics and endoscope design, the decreased size of currently available flexible ureteroscopes makes damage inevitable after repeated use. However, new auxiliary tools may be able to enhance ureteroscope durability.

Urinary calculi in aviation pilots: what is the best therapeutic approach?

Purpose: We reviewed treatment outcomes in a series of aviation pilots treated in the era of modern surgical techniques and provide recommendations regarding treatment in this unique group.

Materials And Methods: We retrospectively analyzed the records of all aviation pilots surgically treated for urinary calculi at our 4 tertiary stone centers from January 1988 to June 2000. Preoperative data and postoperative results were evaluated.

Evaluation of a dissolvable ureteral drainage stent in a Swine model.

Purpose: Ureteral stents are commonly placed after routine ureteroscopic procedures to prevent acute ureteral obstruction. However, stents can cause significant symptoms, may require a secondary procedure for removal and may possibly be forgotten. Toward this end a temporary ureteral drainage stent capable of dissolving spontaneously was developed to obviate the problems associated with more commonly used stents.

Safety and efficacy of holmium: YAG laser lithotripsy in patients with bleeding diatheses.

Purpose: We assessed the safety and efficacy of ureteroscopy and holmium:YAG laser lithotripsy for treating upper urinary tract calculi in patients with known and uncorrected bleeding diathesis.

Materials And Methods: We retrospectively reviewed the charts at 2 tertiary stone centers to identify patients with known bleeding diathesis who were treated with holmium:YAG laser lithotripsy for upper urinary tract calculi. A total of 25 patients (29 upper urinary tract calculi) underwent ureteroscopic holmium laser lithotripsy.

Hypertonic saline-augmented radiofrequency ablation of the VX-2 tumor implanted in the rabbit kidney: a short-term survival pilot study.

Objectives: The increased incidental detection of small (less than 4 cm) renal tumors has stimulated investigations of minimally invasive therapies. Radiofrequency energy is a relatively new and evolving technology that has been used for a variety of experimental and clinical applications. We evaluate the efficacy of hypertonic interstitial saline-augmented radiofrequency therapy to ablate a malignant VX-2 tumor implanted in a rabbit kidney, as measured by the completeness of tumor destruction and progression to metastasis.

The role of stress waves and cavitation in stone comminution in shock wave lithotripsy.

Using an experimental system that mimics stone fragmentation in the renal pelvis, we have investigated the role of stress waves and cavitation in stone comminution in shock-wave lithotripsy (SWL). Spherical plaster-of-Paris stone phantoms (D = 10 mm) were exposed to 25, 50, 100, 200, 300 and 500 shocks at the beam focus of a Dornier HM-3 lithotripter operated at 20 kV and a pulse repetition rate of 1 Hz. The stone phantoms were immersed either in degassed water or in castor oil to delineate the contribution of stress waves and cavitation to stone comminution.

Update on shock wave lithotripsy technology.

Purpose Of Review: Since the first patient was successfully treated with extracorporeal shock wave lithotripsy in 1980, its rapid acceptance and widespread use have championed this form of stone therapy as the treatment of choice for the majority of renal and ureteral calculi. Worldwide clinical series have documented the efficacy and safety of shock wave lithotripsy.

Recent Findings: Shock wave lithotripters have undergone modifications of the source for generation of shock waves, focusing, and even localization techniques since the introduction of the original Dornier HM3 lithotripter.

Routine postoperative imaging is important after ureteroscopic stone manipulation.

Purpose: Improved fiber optics and advanced intracorporeal lithotripsy devices have significantly decreased the incidence of complications during ureteroscopic procedures. Despite recent reports suggesting that radiographic imaging may not be necessary in all individuals after routine ureteroscopy silent obstruction may develop in some, ultimately resulting in renal damage. We determined the incidence of postoperative silent obstruction at our institution and assessed the need for routine functional radiographic studies after ureteroscopy.

Ureteral stents and their use in endourology.

Ureteral stents have assisted urologists in the performance of surgery of the urinary tract for many years. They can have both diagnostic and therapeutic value, but are used most frequently as adjuncts to endoscopic or minimally invasive procedures. This review provides an update of the current uses for ureteral stents, technology of biomaterials, complications associated with indwelling ureteral stents and the future of stents in urology.

Neoinfundibulotomy for the management of symptomatic caliceal diverticula.

Purpose: Direct percutaneous access provides effective treatment for complex caliceal diverticula. Yet, access into the diverticulum alone is usually tenuous and passage of a guide wire across a stenotic infundibulum is often impossible. An alternative technique is described which creates a "neoinfundibulum" to assist in the management of symptomatic caliceal diverticula.