Recent advances in lithotripsy technology and treatment strategies: A systematic review update.

INTRODUCTION: Shock wave lithotripsy (SWL) is a well - established treatment option for urolithiasis. The technology of SWL has undergone significant changes in an attempt to better optimize the results while reducing failure rates. There are some important limitations that restrict the use of SWL. In this review, we aim to place these advantages and limitations in perspective, assess the current role of SWL, and discuss recent advances in lithotripsy technology and treatment strategies. METHODS: A comprehensive review was conducted to identify studies reporting outcomes on ESWL. We searched for literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. Relevant articles in English published since 1980 were selected for inclusion. RESULTS: Efficacy has been shown to vary between lithotripters. To maximize stone fragmentation and reduce failure rates, many factors can be optimized. Factors to consider in proper patient selection include skin - to - stone distance and stone size. Careful attention to the rate of shock wave administration, proper coupling of the treatment head to the patient have important influences on the success of lithotripsy. CONCLUSION: Proper selection of patients who are expected to respond well to SWL, as well as attention to the technical aspects of the procedure are the keys to SWL success. Studies aiming to determine the mechanisms of shock wave action in stone breakage have begun to suggest new treatment strategies to improve success rates and safety.

Lithotripsy and surgery.

Advances in surgical techniques have dramatically altered the management of patients with symptomatic urolithiasis requiring intervention. Extracorporeal shock wave lithotripsy, percutaneous nephrolithotomy, and ureteroscopy allow virtually any stone to be removed from the upper urinary tract without resorting to open surgical techniques. Extracorporeal shock wave lithotripsy is the preferred initial treatment for approximately 80% to 85% of calculi. Percutaneous nephrolithotomy is the preferred approach when dealing with more voluminous stone material (ie, > 2 cm). Ureteroscopy is generally reserved for distal ureteral calculi, although the recent advent of small flexible ureteroscopes have extended ureteroscopic techniques effectively into the proximal ureter and even the kidney. Staghorn stones are usually best managed initially with percutaneous nephrolithotomy followed by the addition of extracorporeal shock wave lithotripsy, if necessary. The relative advantages, disadvantages, and complications of extracorporeal shock wave lithotripsy, percutaneous nephrolithotomy, and ureteroscopy will be reviewed.

Percutaneous transilial access for stone removal in crossed fused renal ectopia.

A case of crossed fused renal ectopia with urosepsis due to multiple struvite calculi in the left lower pole of the orthotopic renal unit is presented. The patient had a neurogenic bladder secondary to myelodysplasia, bilateral ureteral reflux, and had undergone multiple orthopedic operations previously, including posterior iliopsoas transplantation through the iliac bone (Sharrard procedure). After controlling the infection, nephrostolithotomy was performed. Three percutaneous accesses including one through the opening in the left iliac bone were required to gain access to all the stones. The patient was rendered stone free and subsequently underwent bladder augmentation and ureteral reimplantation. The management of complicated renal units is reviewed with respect to crossed renal fusion.

Creatinine kinase concentrations and electrocardiographic changes in extracorporeal shock-wave lithotripsy.

A total of 114 consecutive patients undergoing extracorporeal shock-wave lithotripsy had serial creatinine kinase (CK) with isoenzymes and serial electrocardiograms (ECG). There were significant changes in both heart rate and CK post-lithotripsy. However, this did not appear to be due to elevation of the myocardial component of CK. While there were some random ECG changes pre- and post-lithotripsy, none appeared to be directly related to the procedure.

Percutaneous nephrolithotomy directly through an angiomyolipoma.

We present a patient with tuberous sclerosis and bilateral angiomyolipomas with a right partial staghorn calculi in which the calculi was managed with a percutaneous nephrolithotomy. Despite the inherent risk of hemorrhage with a percutaneous approach compounded by the fact that this was done directly through a tumor, we were able to render the patient stone free with no intraoperative bleeding, complications, or the need for postoperative blood transfusion. To our knowledge, this is the first reported case of percutaneous nephrolithotomy directly through a renal angiomyolipoma.

Treatment of painful caliceal stones.

Nonmobile caliceal stones cause pain more often than previously appreciated. The character and intensity of the pain differs from typical renal colic. Twenty-six patients with caliceal stones and pain underwent attempted treatment for pain control via stone removal or disintegration: 15 were treated with percutaneous stone extraction (PSE), 10 with extracorporeal shock-wave lithotripsy (ESWL), and 1 required open surgery after failing PSE. One patient had persistent pain after ESWL and subsequently underwent PSE; 25 of 26 patients had complete relief of pain. Morbidity was minimal. Patients with painful caliceal stones should be offered ESWL, followed by PSE if pain persists.

Extracorporeal shock wave lithotripsy. Development, instrumentation, and current status.

In this article, the author briefly reviews the early development of the lithotriptor, provides a detailed review of lithotriptors that are currently available, and gives an overview of the present extracorporeal shock wave lithotripsy indications and techniques. The author also presents a brief overview of the results that are produced by various lithotriptors.

Bioeffects of extracorporeal shock-wave lithotripsy. Strategy for research and treatment.

Available information on the bioeffects of ESWL is insufficient to characterize the tissue injury induced by shock waves. The cellular mechanisms have not been elucidated, nor are there enough data to establish objective criteria for treatment.

Extracorporeal shock-wave lithotripsy.

Analysis of our data clearly demonstrates that morbidity, secondary treatment, post-treatment manipulations, and failure of treatment increase as the stone size increases because of the increased stone fragment burden. Patients whose stone burden was less than 2 cm clearly had less morbidity. Composition of the stone may also alter the success of treatment (with cystine, calcium oxalate monohydrate, and brushite stones being resistant to treatment). However, post-treatment morbidity and complications were observed in all categories. Perirenal hematomas are unpredictable by current preoperative testing. Obstruction with pain can occur any time after treatment but usually occurs within the first 48 hours in the majority of patients. Only 1 per cent of our patients required hospitalization in another institution after discharge. Ambulatory ESWL requires that staff at the facility or a urologist be able to observe and appropriately follow the patient for 24 to 48 hours after treatment.

Effect of radiographic contrast material exposure on spiral CT attenuation of renal calculi.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether exposure of renal calculi to radiographic contrast material has an effect on the attenuation values at computed tomography (CT) performed with varying collimation widths. MATERIALS AND METHODS: Renal calculi (23 stones of various composition) were scanned with 1-, 3-, and 10-mm collimation. Stones were then exposed to a solution of radiographic contrast material for 5 minutes, washed with water, and rescanned 36 hours later. The reproducibility of the CT attenuation measurements on different days was evaluated by obtaining measurements in a subset of 16 renal stones on 4 different days. RESULTS: There was no statistically significant change in attenuation after contrast material exposure at narrow collimation. At wider collimation, statistically significant increases were noted in both attenuation and standard deviation. A small amount of variability between readings was noted on different days, with a minimal increase in attenuation each day. Correlation between readings remained very high. CONCLUSION: Exposure of stones to a radiographic contrast material had a statistically significant effect on CT attenuation values only at wide collimation. This may be related to technical factors including volume averaging. Absence of an effect at narrow collimation suggests that the attenuation values of renal stones do not significantly change after exposure to contrast material.

Correction of helical CT attenuation values with wide beam collimation: in vitro test with urinary calculi.

RATIONALE AND OBJECTIVES: Urinary calculi are now commonly detected with helical computed tomography (CT), and it has been proposed that stone composition can be determined from CT attenuation values. However, typical scans are made with a beam collimation of 5 mm or more, resulting in volume averaging and reduction in accuracy of attenuation measurement. The authors tested a model for correction of errors in attenuation values, even at section widths larger than the width of the object. MATERIALS AND METHODS: Human urinary stones were scanned with helical CT at different beam collimation widths. A computer model was used to predict the effect of beam width and stone size on accuracy of measured attenuation. RESULTS: At 3-mm collimation, the model corrected the attenuation readings with an underestimation of 12% +/- 1 (compared with values at 1-mm collimation; 127 stones; diameters of 1.7-11.3 mm). With attenuation measured at 10-mm collimation, the model underestimated the true value by 34% +/- 3 (103 stones), with a significant negative correlation with stone diameter on magnitude of error (diameters of 3.0-11.3 mm). Correlation of data from patient scans with subsequent in vitro scanning of the same stones confirmed the validity of the model, but corrected in vivo scans consistently yielded lower values for the stones than in vitro. CONCLUSION: Volume averaging effects on attenuation in helical CT are predictable in vitro for urinary calculi--and presumably for other roughly spherical structures--as long as section width does not excessively exceed the diameter of the structure.

Value of laparoscopy in the management of calculi complicating renal malformations.

A minimally invasive approach for urolithiasis patients with complex anatomic abnormalities occasionally necessitates the use of laparoscopic techniques, either alone or in combination with endourologic techniques. The management of these patients is best accomplished in centers with the facilities to provide a spectrum of endourologic and laparoscopic techniques. Two illustrative cases are described.

High-speed photographic evaluation of holmium laser.

Little information has been published regarding the relative contributions and exact mechanisms involved in stone fragmentation during holmium laser lithotripsy. High-speed photography has been used to evaluate other intracorporeal lithotripsy devices, and we chose this method to evaluate the holmium laser. High-speed photographic evaluation of cavitation bubbles produced by the four fiber sizes (200, 365, 550, and 1000 microm) showed a moderate degree of correlation (n = 0.71 for 1 J pulses, r = 0.80 for 4 J pulses) between maximal bubble size and fiber diameter. Eliminating the data from the eroded 550 microm fiber strengthened the correlation to r = 0.94 for 1 J pulses and r = 0.99 for 4 J pulses. The importance of keeping fiber tips in good working condition was thereby demonstrated. Evidence of a thermal effect of the laser on stone and chalk was also obtained. In a parallel study, no correlation (r = -0.08) was found between fiber diameter and stone fragmentation efficiency using chalk as an in vitro stone model.

Metabolic evaluation of infected renal lithiasis: clinical relevance.

Complete metabolic evaluation was performed in 21 patients with infected renal lithiasis. Patients with pure struvite stones (struvite +/- carbonate apatite) were significantly less likely to have metabolic abnormalities than patients who had struvite +/- carbonate apatite+calcium oxalate (2 of 14 v 7 of 7, P = 0.0003). Urine calcium excretion was markedly higher in the mixed stone group than the pure struvite group (342 +/- 98 mg/24 h v 136 +/- 82 mg/24 h; P < 0.0001). The differing opinions among researchers regarding the likelihood of finding metabolic abnormalities in patients with urolithiasis and infection probably reflect differences in the definitions of the populations studied. If patients with calculi containing only struvite +/- carbonate apatite are evaluated, we believe that few significant metabolic abnormalities will be identified.

Laparoscopic retroperitoneal needle suspension urethropexy.

Recent advances in laparoscopic surgery have allowed urologists to perform laparoscopic bladder suspension; however, laparoscopic suturing techniques have a steep learning curve and make the procedure more difficult and time consuming. We describe a new technique that combines extraperitoneal laparoscopic bladder neck mobilization through a single port with the ease of a needle suspension urethropexy in order to avoid the need for vaginal incisions and the use of laparoscopic suturing techniques. The procedure has been performed in four patients, all of whom are continent and voiding with complete bladder emptying. Postoperative pain was minimal, allowing most patients to be discharged the day after surgery. In the future, the procedure may be performed on an outpatient basis.

Endoscopic management of total ureteral occlusion and ureterovaginal fistula.

Between August 1991 and June 1994, endoureterotomy was performed in nine patients for total ureteral occlusion. Four of these patients had an associated ureterovaginal fistula. The total ureteral occlusions were iatrogenic in eight patients and the result of trauma in one. The prone split leg position was used to facilitate simultaneous antegrade and retrograde ureteroscopy in all nine patients. The "cut-to-the-light" technique was utilized in six patients and a new technique employing a fascial incising needle was used in five patients. Five patients developed ureteral strictures within 5 months of the primary procedure that were corrected endoscopically. With a mean follow-up of 22 months, all nine patients have a successful outcome. Endoscopic management of difficult urteral disease such as total urteral occlusion and ureterovaginal fistula is a useful alternative to open surgery.

Effects of SWL on glomerular filtration rate and renal plasma flow in uninephrectomized minipigs.

This study tested the hypothesis that the effects of SWL on hemodynamics in solitary kidneys differ from those in kidneys of binephric animals. Five female miniature pigs (Pitman-Moore, 6 months of age, 30-35 kg) were anesthetized for unilateral nephrectomy. Seven pigs served as binephric controls. Two weeks later, each pig was anesthetized, prepared for unilateral or bilateral urine collections, and subjected to SWL (Dornier HM3, 2000 shocks, 24 kV). Clearances of inulin (glomerular filtration rate; GFR) and para-aminohippurate (renal plasma flow; RPF) were measured 1 hour prior to and 1, 4, and 24 hours after SWL. The GFR and RPF were higher in uninephrectomized than in intact pigs at all time points. In both groups, SWL reduced GFR and RPF. In the binephric pigs, RPF was reduced at all times post-SWL, but in the uninephrectomized pigs, RPF was returning toward baseline by 4 hours post-SWL and was not different from baseline at 24 hours. A comparison of whole-animal GFR and RPF (righ plus left clearances in binephric pigs v solitary renal clearances in uninephrectomized pigs) showed that whole-animal GFR and RPF did not differ between the groups before or after SWL. Compensatory renal hypertrophy and improved hemodynamics in solitary kidneys may acutely attenuate the renal vasoconstrictive effect of SWL. The long-term consequences of the compensatory changes are unknown.

Metabolic evaluation of stone disease patients: a practical approach.

In the last three decades, minimally invasive techniques have progressed significantly, replacing traditional open surgery as the mainstay of stone disease surgical treatment. The challenge for the next millennium remains medical prevention of calcium urolithiasis, a field where less dramatic progress has been achieved during the same period of time. The purpose of this article is to provide the practicing urologist with current practical guidelines for the assessment and management of calcium urolithiasis patients. The recommendations are based on the latest available information regarding the pathogenesis, medical treatment options, and decision-making rationale when managing these challenging patients. Every urolithiasis patient should undergo a basic evaluation, which is considered the minimal essential diagnostic work-up, in order to rule out obvious, treatable systemic causes of urinary stone disease. All patients should be advised about conservative nonspecific preventive measures. High-risk stone patients should have a more extensive metabolic evaluation based on two 24-hour urine samples. Treatment protocols for each patient are tailored individually according to the metabolic evaluation findings.

Expanding role of flexible nephroscopy in the upper urinary tract.

Flexible nephroscopy has become an important diagnostic and therapeutic modality for urologists. We have applied the flexible nephroscope in four clinical settings: as an adjunct to rigid instruments during primary percutaneous nephrolithotomy (PCNL); in a second-look procedure to remove residual renal calculi; as the primary endoscope to treat renal calculi; and to diagnose and treat other upper urinary tract pathology. The most common application of flexible nephroscopy in our experience has been during primary PCNL after the bulk of the stone burden has been removed with the rigid nephroscope. Liberal use of the flexible endoscope in these settings may increase the stone-free rate and decrease the need for additional access tracts and procedures. In addition, patients with conduit urinary diversions may be managed using flexible nephroscopy to diagnose and treat upper tract tumors.

Biocompatibility of small-intestinal submucosa in urinary tract as augmentation cystoplasty graft and injectable suspension.

We explored the biocompatibility of fluidized canine small-intestinal submucosa (SIS) for periureteral injection and as a patch graft for bladder augmentation in pigs. Gross evaluation 8 weeks after submucosal injection showed persistence of the nodule. Histologic examination showed thickened submucosa with spindle cells embedded in poorly organized fibrous material. There was no evidence of inflammatory reaction or granuloma formation. Subserosal nodules likewise persisted and demonstrated capillary ingrowth. Grafts of SIS became epithelialized within 3 weeks with maintenance of bladder capacity. Ingrowth of capillaries and smooth muscle could be seen in later specimens. Although further studies with longer follow-up are needed, SIS appears to be a promising graft material in the urinary tract.