Efficiency and efficacy of different intracorporeal ultrasonic lithotripsy units on a synthetic stone model

Intracorporeal lithotripsy

Since the introduction of ESWL, PNL and URS during the early 1980s the application rate of ESWL has declined while those of PNL and URS have increased. This is mainly due to the facts that instruments and techniques for Intracorporeal Lithotripsy (IL) have made a continuous progress. This review shows that today an array of options for IL within the entire urinary tract is available to treat stones in a perfect minimal invasive way. At the same time further improvements of IL are already visible.

Comparison of ultrasonic and pneumatic intracorporeal lithotripsy techniques during percutaneous nephrolithotomy

OBJECTIVES

To compare the effectiveness and safety of ultrasonic and pneumatic lithotripters in the treatment of renal stone disease.

MATERIALS AND METHODS

A total of 227 consecutive percutaneous nephrolithotomy procedures for renal calculi were performed. In 107 patients ultrasonic lithotriptors were used (group I) and in 83 patients pneumatic lithotriptors were used (group II). In the remaining 37 patients, stones were managed with both pneumatic and ultrasonic lithotripters. Follow-up studies included intravenous urography (IVU) and/or computed tomography (CT).

RESULTS

The mean operative time and duration of hospitalization were similar between the groups. In the ultrasonic treatment group, 100 (96.9%) patients were stone-free on postoperative day 1 and 5 (4.6%) went on to undergo an additional treatment modality, resulting in a total stone-free rate of 97.2%. In the pneumatic lithotripsy group, 68 (81.9%) patients were stone-free after the primary procedure on the first day and 15 (18.1%) went on to undergo an additional treatment modality, resulting in a stone-free rate of 91.5%. The final stone-free rates at 3 months postoperatively in groups I, II, and III were 97.2%, 91.5%, and 87.9%, respectively (P = 0.826).

CONCLUSIONS

We conclude that both ultrasonic and pneumatic lithotripters are effective and safe for intracorporeal lithotripsy. However, the ultrasonic lithotripter provides higher stone-free rates with similar morbidity compared with pneumatic devices.

Tissue effects of intracorporeal lithotripsy techniques during percutaneous nephrolithotomy: comparison of pneumatic and ultrasonic lithotripters on rat bladder

The objectives of this study were to determine the tissue effects of ultrasonic and pneumatic lithotripsy on the rat urothelium. The rats were divided into three groups. Groups I and II consisted of ten rats each that underwent intracorporeal lithotripsy (pneumatic and ultrasonic lithotripsy, respectively). Group III contained ten control rats and no lithotripsy method was used, they served as references for absence of injury. The light microscopy findings were evaluated as follows: squamous metaplasia, papillary projection, inflammation, increased stratification, and stone formation. In five (71.4%) animals of group II, bladders were edematous and hemorrhagic, macroscopically. Histologically, the bladder wall was normal in four rats of group I and in one of group II. There was a significant increase in inflammation (31.5%), squamous metaplasia (85.7%), papillary projection (71.4%), increased stratification (71.4%), and microscopic or macroscopic stone formation (85.7%) in the bladder wall of group II rats in comparison with group I and control group. In the rat model, we noted that ultrasonic devices have a potential risk for tissue injury. In turn, this was associated with a markedly increased deposition of CaOx stones in the kidney. When confronted with harder stones, pneumatic lithotripsy can be more effective while also minimizing tissue injury.

In vitro evaluation of the Lithoclast Ultra Vario combination lithotrite

Rigid intracorporeal lithotrites can be invaluable in the removal of large stone burdens during percutaneous nephrolithotomy. One such device, the Lithoclast Ultra Vario (LUV) has an outer ultrasound probe and inner pneumatic-ballistic probe. The ballistic probe can be advanced or retracted and run at 1-12 Hz. Since it can be difficult to predict optimal settings with any new device, we asked if in vitro testing could give insight into how best to operate this lithotrite. We tested the LUV under hands-free conditions that simulate treatment of fixed stones and freely movable stones. A fixed-stone test system measured the time to penetrate a gypsum model stone placed atop the probe and a movable-stone system determined time for comminution of a stone within a confined space. In addition, the time to evacuate 2-mm stone particles was measured. For hands-on testing, model stones were placed in a plastic dish submerged in water and the time to comminution was measured. Penetration time of fixed stones was faster with the ballistic probe extended 2.5 mm than when retracted (5.30 ± 0.85 vs. 8.75 ± 1.07 s, p < 0.0001). Comminution of free stones was faster with the ballistic probe retracted than when it was extended 1 mm or 2.5 mm (9.7 ± 0.9, 13.8 ± 1.3, 23.7 ± 3.2 s, p < 0.0001). In hands-on testing, extending the ballistic probe substantially reduced the efficiency of comminution (36.7 ± 6.4 vs. 131.3 ± 15.3 s, p < 0.0001). Clearance of fragments was considerably faster when the pneumatic-ballistic rate was 12 Hz compared to 1 Hz (12.3 ± 1.1 vs. 28.3 ± 2.2 s, p < 0.0001). These in vitro findings suggest ways to take advantage of the positive features while minimizing potential limitations of this lithotrite. Extending the ballistic probe is an advantage when the stone is immobile, as would be the case in treating a large stone that can be isolated against the wall of the pelvicalyceal system, but is a distinct disadvantage--due to retropulsion--when the stone is free to move. Operation of the LUV at fast ballistic rate significantly improved its ability to aspirate stone fragments.

Surgical management of stones: new technology

In recent years, the surgical treatment of kidney stone disease has undergone tremendous advances, many of which were possible only as a result of improvements in surgical technology. Rigid intracorporeal lithotrites, the mainstay of percutaneous nephrolithotomy, are now available as combination ultrasonic and ballistic devices. These combination devices have been reported to clear a stone burden with much greater efficiency than devices that operate by either ultrasonic or ballistic energy alone. The laser is the most commonly used flexible lithotrite; advances in laser lithotripsy have led to improvements in the currently utilized Holmium laser platform, as well as the development of novel laser platforms such as Thulium and Erbium devices. Our understanding of shock wave lithotripsy (SWL) has been improved over recent years as a consequence of basic science investigations. It is now recognized that there are certain maneuvers with SWL that the treating physician can do that will increase the likelihood of a successful outcome while minimizing the likelihood of adverse treatment-related events.

Prospective randomized comparison of a combined ultrasonic and pneumatic lithotrite with a standard ultrasonic lithotrite for percutaneous nephrolithotomy

PURPOSE

To compare the efficiency and cost effectiveness of a combined pneumatic and ultrasonic lithotrite (Lithoclast Ultra) and a standard ultrasonic lithotrite, (LUS-1) during percutaneous nephrolithotomy.

MATERIALS AND METHODS

In a prospective randomized trial, 30 patients undergoing percutaneous nephrolithotomy (PCNL) were randomized to PCNL with either the combined pneumatic and ultrasonic lithotrite (PUL) or a standard ultrasonic lithotrite (SUL). Patient demographics, stone composition, location, pre- and post-operative stone burden, fragmentation rates, and device failures were compared.

RESULTS

There were 13 patients in the PUL group and 17 patients in the SUL group. Stone burden and location were equal. Overall, 64% of the PUL group had hard stones (defined as stones that were either pure or a mixture of cystine [3], calcium oxalate monohydrate [CaOxMono; 2], and calcium phosphate [CaPO4; 2]), and four had soft stones (3 struvite and 1 uric acid [UA]). In the SUL group, there were eight hard stones (5 CaOxMono and 3 CaPO4), and six soft stones (4 calcium oxalate dihydrate [CaOxDi] and 2 UA) (P = 0.51). Stone composition data were unavailable for five patients. Fragmentation time for the PAL was 37 minutes versus 31.5 minutes for the SUL (P = 0.22). Stone retrieval and mean operative times were similar for both groups. There were a total of three (23.1%) device-related problems in the PUL group, and eight (47%) in the SUL group. There was one (7.7%) device malfunction in the PUL group due to probe fracture. There were two (11.7%) device failures in the SUL group; one failure required the device to be reset every 30 minutes, and the second was an electrical failure. Suction tubing obstruction occurred twice (15.3%) in the PUL group and 35.3% in the SU group (P = 0.35). The stone-free rates for the PUL and SUL were 46% and 66.7%, respectively (P = 0.26).

CONCLUSION

Although the PUL was more costly, stone ablation and clearance rates were similar for both the combined pneumatic and ultrasonic device and the standard ultrasonic device. When stratified with respect to stone composition, the PUL was more efficient for harder stones, and the SUL was more efficient for softer stones.

In Vitro Assessment of Ultrasonic Lithotriptors

PURPOSE

Ultrasonic lithotriptors are commonly used to fragment and remove stones during percutaneous nephrolithotomy. To date a comparative assessment of current units has not been accomplished without potential operator bias. An objective testing environment is required for optimal appraisal of the efficiency of ultrasonic lithotriptors.

MATERIALS AND METHODS

An in vitro test system was devised to evaluate the ability of ultrasonic lithotriptors to core through artificial stones. The system consisted of an irrigation sheath (Cook Urological, Spencer, Indiana) through which ultrasonic probes were placed. Ultrasonic hand pieces and probes were secured in an upright position. An Ultracal-30 (U.S. Gypsum, Chicago, Illinois) stone cylinder (mean length 12.8 +/- 0.6 mm, mean diameter 7.6 +/- 0.07 mm) was centered on the probe tip. A weight (62.7 gm) was placed atop the stone to provide a constant force. We evaluated the Olympus LUS-1 and LUS-2 (Olympus, Melville, New York), Circon-ACMI USL-2000 (Circon-ACMI, Southborough, Massachusetts), Karl Storz Calcuson (Karl Storz, Culver City, California) and Richard Wolf model 2271.004 (Richard Wolf, Vernon Hills, Illinois). All probes had outer diameters of 3.4 mm except for the Circon-ACMI unit (3.8 mm). Using 100% power settings times for complete stone penetration were assessed for all units. Differences in mean stone penetration times were compared using ANOVA.

RESULTS

The Olympus LUS-2 had the fastest mean stone penetration time (28.8 +/- 2.7 seconds). This value was used to normalize the data into efficiency ratios, where other unit times were expressed as multiples of the LUS-2 time: Olympus LUS-2 (1.0 +/- 0.1) equals Circon-ACMI USL-2000 (1.1 +/- 0.3) greater than Karl Storz Calcuson (1.4 +/- 0.3) greater than Olympus LUS-1 (2.1 +/- 0.5) greater than Richard Wolf (3.6 +/- 0.8). Efficiencies of the LUS-2 and USL-2000 units were essentially equivalent, with all others significantly less efficient (p <0.05).

CONCLUSIONS

This new in vitro testing model provides an objective, reproducible method for evaluating the efficiency of intracorporeal lithotriptors. Of the units tested the Olympus LUS-2 and Circon-ACMI USL-2000 were the most efficient.

Intracorporeal lithotripsy: which modality is best?

PURPOSE OF REVIEW

A large number of related articles published within the last year were reviewed. Different types of intracorporeal lithotripter devices were compared according to their advantages, disadvantages, efficacy, safety and clinical applications. General directions of future developments are discussed.

RECENT FINDINGS

Ultrasound lithotripters employed through rigid endoscopes provide high fragmentation rates (97-100%) and stone free rate (94%). Clinical evaluation of a new combination ultrasound and pneumatic lithotripter reported an overall stone free rate of 80-89.7%. No major complications were observed. The holmium:YAG (Yttrium-Aluminum-Garnet) laser lithotripter is able to destroy all compositions of stone. The stone free rate for ureteral stones is close to 100%. Complications are rare and minimal. Newer wavelengths such as erbium:YAG are currently impractical. There are limited clinical data regarding frequency-doubled double-pulse neodymium:YAG laser lithotripsy.

SUMMARY

Ultrasound lithotripsy is still the preferable modality applied through rigid endoscopes. A new combination of ultrasound and pneumatic impactor includes the advantages of each mode. The holmium:YAG laser lithotripter is the method of choice for flexible endoscopic procedures. Further development of new lithotripters with different energy sources and their combination is necessary.