Effect of modification of shock-wave delivery on stone fragmentation

Evaluation of the optimal frequency of and pretreatment with shock waves in patients with renal stones

Purpose

Many studies have been carried out to increase the success rate of shock wave lithotripsy (SWL) and to reduce renal injury. We investigated the success rate after one session as well as urine N-acetyl-β-d-glucosaminidase (NAG) levels for the evaluation of renal injury according to shock wave frequency and pretreatment with low-energy shock waves during SWL.

Materials and Methods

The study targeted 48 patients with renal stones who had undergone SWL. Patients were sequentially allocated into four groups according to shock wave frequency (60 or 120 shocks/min) and whether pretreatment had occurred. We documented total SWL operating number, success rate after first SWL, urine NAG, compliance, and the total cost for each patient.

Results

There were 32 males and 16 females with an average age of 51.6 years. The average stone size was 7.06 mm, and there was no significant difference in stone size between the groups. The data showed that patients treated with a frequency of 60 shocks/min had a lower mean number of SWL sessions, 1.36 sessions for 60 shocks/min and 2.0 sessions for 120 shocks/min, respectively, which was statistically significant (p<0.05). When comparing NAG/creatinin ratios before and after SWL between those with and without pretreatment, there was no significant difference according to pretreatment (p=0.406).

Conclusions

SWL treatment at a frequency of 60 shocks/min yielded better outcomes, such as a lower number of SWL sessions, and had an increased success rate compared with SWL at 120 shocks/min. On the other hand, pretreatment did not impact renal injury. Therefore, SWL treatment at a frequency of 60 shocks/min could improve treatment efficacy more than that for SWL at 120 shocks/min.

Comparison between two shock wave regimens using frequencies of 60 and 90 impulses per minute for urinary stones

PURPOSE

Two different regimens of SWL delivery for treating urinary stones were compared.

METHODS

Patients with urinary stones were randomly divided into two groups, one of which received 3000 shocks at a rate of 60 impulses per minute and the other of which received 4000 shocks at 90 impulses per minute. Success was defined as stone-free status or the detection of residual fragments of less than or equal to 3 mm three months after treatment. Partial fragmentation was considered to have occurred if a significant reduction in the stone burden was observed but residual fragments of 3mm or greater remained.

RESULTS

A total of 143 procedures were performed with 3000 impulses at a rate of 60 impulses per minute, and 156 procedures were performed with 4000 impulses at 90 impulses per minute. The stone-free rate was 53.1% for patients treated with the first regimen and 54.8% for those treated with the second one (p = 0.603). The stone-free rate for stones smaller than 10 mm was 60% for patients treated with 60 impulses per minute and 58.6% for those treated with 90 impulses per minute. For stones bigger than 10 mm, stone-free rates were 34.2% and 45.7%, respectively (p = 0.483). Complications occurred in 2.3% of patients treated with 60 impulses per minute and 3.3% of patients treated with 90 impulses per minute.

CONCLUSION

No significant differences in the stone-free and complication rates were observed by reducing the total number of impulses from 4000 to 3000 and the frequency from 90 to 60 impulses per minute.

[The future of ESWL]

With the introduction of the Dornier HM3 lithotripter, the successful history of extracorporeal shock wave lithotripsy (ESWL) for noninvasive treatment of urinary stones began about 25 years ago. The development of newer lithotripters has not been able to improve clinical efficacy because the shock wave parameters specifically responsible for stone disintegration or tissue trauma and pain induction have not yet been identified. Actual research in lithotripter technology deals with modification of the focal point. The evolution of endoscopic procedures, ureterorenoscopy, and percutaneous nephrolithotomy took longer but was more successful in terms of clinical efficacy. Nowadays, ESWL or an endoscopic procedure is offered as a reasonable option for most urinary stone cases. Therefore, economic aspects and the surgeon's expertise will become greater factors when a procedure is chosen. ESWL, with or without anaesthesia, will be an inherent part of future treatment modalities for urinary stones.

Optimizing Shock Wave Lithotripsy in the 21st Century

OBJECTIVE

Shock wave lithotripsy (SWL) has radically changed treatment of stone disease and appears to be the first option for the majority of patients. This review of current literature focused on suggestions for optimising technique, patient selection, results, and lithotriptor comparison for SWL.

METHODS

Literature search for SWL was performed for recently published papers in English language. Topics of interest were treatment protocols; patient evaluation; pre-SWL prediction of outcome; lithotriptor technology; efficacy; and methods to assess the effects, decrease complications, and compare lithotriptors. Earlier classic papers on SWL and guidelines for stone disease were also reviewed.

RESULTS

Recent literature contained important recommendations about SWL concerning (1) methods to predict stone fragmentation; (2) identification of factors contributing to treatment failure for lower pole and ureteric calculi; (3) guidelines from urological associations; (4) manoeuvres and changes in SWL delivery (slower rate, twin-pulse technique) to increase efficacy and decrease complications; (5) clarification of the role of medical treatment (antibiotics, alpha-blockers); (6) role of SWL in calyceal stones, CIRF, and abnormal kidneys; (7) obesity and SWL; and (8) methods to evaluate and compare lithotriptors.

CONCLUSIONS

SWL delivered in an outpatient setting as an anaesthesia-free treatment is still considered the first option for the majority of stones with a minimal number of complications. Better understanding of the physics of shockwave delivery is required, together with treatment optimisation by limiting renal damage and better selection of patients because this approach will offer maximum benefit to patients and physicians, as well as more cost-effective treatment.