The use of shock wave lithotripsy for renal calculi

The effect of focus size and intensity on stone fragmentation in SWL on a piezoelectric lithotripter

Purpose

We aim to analyze the efficacy of different focus sizes and the influence of pulse pressure (intensity) during shock wave lithotripsy (SWL) in terms of stone fragmentation.

Methods

Combination of three focal sizes (F1 = 2 mm, F2 = 4 mm, F3 = 8 mm) and 11 output pressure settings (intensity 10–20) of a piezoelectric lithotripter (Wolf PiezoLith 3000) were tested on artificial stones (n = 99). The stones were placed within a 2 mm mesh cage. The needed number of shockwaves (SW) to first visible crack, 50% and 100% stone disintegration were recorded.

Results

Similar number of SW’s were observed until the first crack 10, 11 and 11 SW’s for F1, F2, and F3, respectively (p > 0,05). The median number of SW needed for 50% stone disintegration was 245 for F1 group, 242 for F2 group and 656 for F3 group. F1 vs F2 p = 0.7, F1 vs F3 and F2 vs F3 p < 0.05. Similarly, with larger focus size a higher number of shockwaves were necessary for 100% stone disintegration. 894, 877 and 1708 SW’s for F1, F2 and F3, respectively. Only for F1 vs F3 and F2 vs F3 (all p < 0.05) a statistical difference was observed. These findings were consistent in all different power settings, with an increased difference in lower power levels (≤ 14).

Conclusions

A smaller focus size, as well as a higher peak pressure results in a more effective stone fragmentation. However, these results need to be confirmed in an in vivo setting with multiple parameters interfering the efficacy, like BMI, respiration or stone migration.

Audiovisual distraction reduces pain perception during shockwave lithotripsy

BACKGROUND AND PURPOSE

Lithotripsy is an established method to fragment kidney stones that can be performed without general anesthesia in the outpatient setting. Discomfort and/or noise, however, may deter some patients. It has been demonstrated that audiovisual distraction (AV) can reduce sedoanalgesic requirements and improve patient satisfaction in nonurologic settings, but to our knowledge, this has not been investigated with lithotripsy. This randomized controlled trial was designed to test the hypothesis that AV distraction can reduce perceived pain during lithotripsy.

PATIENTS AND METHODS

All patients in the study received identical analgesia before a complete session of lithotripsy on a fixed-site Storz Modulith SLX F2 lithotripter. Patients were randomized to two groups: One group (n=61) received AV distraction via a wall-mounted 32″ (82 cm) television with wireless headphones; the other group (n=57) received no AV distraction. The mean intensity of treatment was comparable in both groups. Patients used a visual analogue scale (0-10) to record independent pain and distress scores and a nonverbal pain score was documented by the radiographer during the procedure (0-4).

RESULTS

In the group that received AV distraction, all measures of pain perception were statistically lower. The patient-reported pain score was reduced from a mean of 6.1 to 2.4 (P<0.0001), and the distress score was reduced from a mean of 4.4 to 1.0 (P=0.0001). The mean nonverbal score recorded by the radiographer was reduced from 1.5 to 0.5 (<0.0001).

CONCLUSIONS

AV distraction significantly lowered patients' reported pain and distress scores. This correlated with the nonverbal scores reported by the radiographer. We conclude that AV distraction is a simple method of improving acceptance of lithotripsy and optimizing treatment.

Failure after shockwave lithotripsy: is outcome machine dependent?

AIM

To investigate the issue of shockwave lithotripsy failure by studying the effect of machine crossover to the Technomed Sonolith Vision (TSV) lithotriptor in patients with previously unsuccessfully treated renal stones with the Dornier Compact Delta (DCD). Records were examined for the period between 1998 and 2006. Parameters analysed were: size, multiple/single stones, location, treatments/stone.

RESULTS

Seventy-six patients fulfilled the inclusion criteria. Following lithotripsy with the TSV, the stone-free rate (SFR) at 3 months was 56.7%, and the success rate (stone-free and fragments < or = 4 mm, SR) 86.7%. Twenty-two patients had multiple stones and the majority of the stones were located in the lower calyx (59.2%). Mean size was 8.9 mm prior to treatment with the TSV machine (10.2 mm for DCD). Further analysis followed in a subgroup of 42 patients of the same stone size (+/-2 mm) before and after DCD sessions. Mean stone size was 7 mm. The SFR was 61.9% (62.9% vs. 40.9% for single and multiple stones), and the SR was 88.1%. No difference in SFR was found for single or multiple stones in any of the two groups.

CONCLUSIONS

The term 'extracorporeal shockwave lithotripsy (ESWL)-resistant stones' needs to be re-examined, as treatment with a different lithotriptor was successful in a group of stones where another machine had failed. Lithotripters with different shock wave characteristics may result in difference in the results of ESWL. Future research in ESWL should focus on stone characteristics and development of machines with the ability to adapt to specific stone features.

Eighteen-year experience with the Medstone STS lithotripter: safety, efficacy, and evolving practice patterns

OBJECTIVE

To evaluate trends in safety, efficacy, and practice patterns for shockwave lithotripsy (SWL) procedures performed during a 18-year period and correlate the findings with recent evidence-based practice guidelines.

MATERIALS AND METHODS

From January 1988 to June 2006, 66,819 SWLs were performed using the Medstone STS lithotripter in patients with radiologic evidence of stones in the kidney or ureter. Treatment characteristics, such as stone location and size, need of re-treatment, and final success rate were recorded. The procedures were further divided by year for statistical consideration. Statistical analysis was performed using Student t test; P < 0.05 was considered significant.

RESULTS

Overall SWL success rate was 85% (39,667/46,669), and the overall re-treatment rate was 7.2% (3,417/46,669). There was no significant change in the overall proportion of lower-pole calculi managed with SWL, although there was a significant decrease in the proportion of SWL used for lower calix stones larger than 16 mm in the time period after 2000 (P = 0.006). There was a steady increase in the number of procedures performed for renal calculi in other locations per year, in particular for intrarenal calculi smaller than 20 mm. Intrarenal stones larger than 30 mm decreased as a proportion of procedures per year (P = 0.048) There was no significant change in the proportion of upper and distal ureteral stones managed, corresponding to a solid plateau in the percentage of SWL performed per year.

CONCLUSION

Our study did not demonstrate an overall drop in SWL; however, it did show the interference of endoscopic procedures on two case scenarios. There was a significant decrease (P = 0.048) in SWL for renal stones larger than 30 mm, and the same trend was noted for lower calix stones larger than 15 mm (P = 0.06).

The role of extracorporeal shockwave lithotripsy in an asymptomatic special patient group with small renal calculi

BACKGROUND AND PURPOSE

Data concerning extracorporeal shock wave lithotripsy (SWL) management of small (< or = 5 mm) asymptomatic renal caliceal stones are lacking in the literature. In this study, we aimed to determine the effectiveness of SWL in a special group of patients who had very small (< or = 5 mm) asymptomatic renal caliceal stones. The group of patients consisted of pilots, gendarmes, and soldiers, such as commandos, for whom treatment was obligatory and who had to be stone free because of their military duties.

PATIENTS AND METHODS

We retrospectively examined SWL data and retrieved information for 84 patients with small asymptomatic renal caliceal stones. The SWL sessions were performed with a Siemens Lithostar lithotriptor. The mean age of the patients was 34 +/- 13 years. The mean stone size was 4.8 +/- 0.4 mm. The mean numbers of shockwaves and energy used were 2707 +/- 1742 and 18 +/- 2 kV, respectively. The location of stones were: 11 right upper calix, 10 right middle calix, 17 right lower calix, 13 left upper calix, 16 left middle calyx, and 17 left lower calix. Eighty-four patients underwent 101 SWL sessions. Only eight patients had second and three patients had third SWL treatments. SWL was performed five times for only one patient. All mean values were realized with an SPSS 10.0 statistical program.

RESULTS

After the first, second, and third SWL sessions, the stone-free rate was calculated as 87%, 93% and 94%, respectively. Only five patients with lower renal caliceal stones were not stone free. The reported complications were macroscopic hematuria necessitating medical attention in four patients, skin ecchymosis in seven patients, severe colic pain in two patients, and urinary-tract infection in one patient. There was no need for hospitalization for these complications.

CONCLUSION

SWL is effective and safe in patients with very small (< or = 5 mm) asymptomatic renal caliceal stones in all locations.

Success in Treating Renal Calculi with Single-Access, Single-Event Percutaneous Nephrolithotomy: Is a Routine "Second Look" Necessary?

BACKGROUND AND PURPOSE

Percutaneous nephrolithotomy (PCNL) is an effective procedure for the treatment of large renal calculi. An important consideration for patients undergoing PCNL is the management of any residual stone burden, which may include "second-look" nephroscopy. The utility of this practice is unproven, and we present our data on a series of patients in which second-look procedures were not performed.

PATIENTS AND METHODS

We retrospectively reviewed the records of 43 consecutive patients undergoing a total of 45 procedures by a single surgeon at a tertiary-care center. Patients were considered stone free if no calculi were evident by either plain film or noncontrast CT scan. Statistical analysis was used to look for correlations between radiographic stone clearance and various patient and stone characteristics.

RESULTS

Of these procedures, 15% had immediate postoperative evidence of residual fragments. At a mean follow-up of 8 months, 32.5% had residual or recurrent stone. There were statistically significant correlations between both patient age and stone size and the risk of recurrent or residual stone.

CONCLUSIONS

In our study, PCNL was effective for the single-stage treatment of large renal calculi. Aggressive stone clearance obviated the need for routine second-look nephroscopy. Factors leading to an increased risk of residual or recurrent calculi included the presence of a staghorn calculus and younger patient age. The excellent stone-free rates achieved suggest that routine second-look nephroscopy may not be necessary for the majority of patients undergoing PCNL.

Effect of modification of shock-wave delivery on stone fragmentation

PURPOSE OF REVIEW

Shock-wave lithotripsy has been the mainstay of urinary-stone treatment over the past 20 years, with three generations of lithotripters now in the market place. Little improvement, however, has been made in the overall efficiency, since the original Dornier HM3 lithotripter. Over the past 5 years much progress has been made in the basic research of shock-wave lithotripsy, with better understanding of the mechanisms involved in stone fragmentation. This progress has led to new modifications in the way shock-wave pulse is generated and delivered.

RECENT FINDINGS

Clinical studies, reflecting improved understanding of basic mechanisms of stone comminution, are being published. Two recent prospective clinical trials have shown the higher efficiency of slow-rate compared with fast-rate shock-wave lithotripsy. A very practical solution requiring no hardware upgrade albeit at longer procedure times. Other promising developments include the use of twin-head technology, with either simultaneous or sequential shock waves. In addition, chemolytic pretreatment and dose-escalation techniques have shown early encouraging results. This review provides an update of the latest shock-wave technology and delivery strategies.

SUMMARY

Long-term studies, to document anticipated improved safety with slow shock-wave rate, are needed. Future in-vivo and clinical studies of twin-head technology and dose-escalation strategy of shock-wave lithotripsy may initiate new lithotripter designs that will lead to improved stone-free rates, while simultaneously reducing associated renal trauma.

Extracorporeal shock wave lithotripsy 25 years later: complications and their prevention

OBJECTIVE

We review the pathophysiology and possible prevention measures of complications after extracorporeal shock wave lithotripsy (ESWL).

METHODS

A literature search was performed with the Medline database on ESWL between 1980 and 2004.

RESULTS

ESWL application has been intuitively connected to complications. These are related mostly to residual stone fragments, infections, and effects on tissues such as urinary, gastrointestinal, cardiovascular, genital, and reproductive systems. Recognition of ESWL limitations, use of alternative therapies, correction of pre-existing renal or systemic disease, treatment of urinary tract infection, use of prophylactic antibiotics, and improvement of ESWL efficacy are the most important measures of prevention. Decrease of shock wave number, rate and energy, use of two shock-wave tubes simultaneously, and delivery of two shock waves at carefully timed close intervals improve ESWL efficacy and safety.

CONCLUSION

ESWL is a safe method to treat stones when proper indications are followed. The need for well-designed prospective randomised trials on aetiology and prevention of its complications arises through the literature review.