Fragmentation of biliary calculi by means of extracorporeally generated piezoelectric shock waves

Ten years experience with piezoelectric extracorporeal shockwave lithotripsy of gallbladder stones

BACKGROUND

A critical review of the experience with extracorporeal shockwave lithotripsy (ESWL) of gallbladder stones is needed to clarify whether this method should continue to be applied to patients.

METHODS

Patients with symptomatic gallbladder stones were treated by piezoelectric ESWL according to a prospective protocol between 1988 and 1997. ESWL treatment was limited to a maximum of three (solitary stones <20 mm diameter) to five sessions (larger solitary or multiple stones) and 3000 pulses per session. Univariate and multivariate analyses of pretreatment and treatment variables were performed to investigate their impact on fragmentation efficacy and stone clearance. A tree-based analysis was used to identify prognostically homogenous subgroups of individuals with maximum benefit from ESWL.

RESULTS

Four hundred and eight patients, 76% female and 24% male, with a mean age of 46 (SD, 13) years, were selected for evaluation. Cox regression analysis identified three pretreatment variables with significant prognostic impact: (1) number of gallstones >1 (relative risk, 2.6 (95% CI, 1.9-3.5)), (2) size of stones >17 mm (1.7 (1.4-2.2)), and (3) computed tomography (CT) density of stones >55 Hounsfield units (H) (1.4 (1.1-1.8)). According to tree-based analysis, the stone clearance rate after 1 year was 85% (95% CI, 75-91%) for solitary stones <16 mm, 79% (70-86%) for solitary stones > or =16 mm with a CT density <84 H, 45% (32-55%) for solitary stones > or =16 mm with a CT density > or =84 H, and 42% (30-51%) for multiple stones. Five years after stone clearance, recurrence occurred in 43% of patients (95% CI, 39-47%).

CONCLUSIONS

ESWL treatment showed an acceptable stone clearance in the case of small solitary gallbladder stones (<16 mm) or larger solitary stones with a CT density <84 H, but a very low success rate in the case of multiple stones. The poor long-term success, however, is an important argument against the use of ESWL of gallbladder stones.

Pulverisation of calcified and non-calcified gall bladder stones: extracorporeal shock wave lithotripsy used alone

Using a modified electromagnetic lithotripter (Siemens), extracorporeal shock wave lithotripsy (ESWL) was performed in 260 patients with gall bladder stones. Exclusion criteria for treatment were a non-functioning gall bladder, subcostal gall bladder location, and multiple stones occupying more than three quarters of the gall bladder volume. Stone pulverisation was the end point of ESWL. The number of shock wave discharges and sessions was not limited. Pulverisation was achieved in 250 patients (96.1%) after a median of three ESWL sessions (range 1-21). The number of sessions required depended upon stone composition and burden. More than three sessions were required in 60.2% of patients with calcified stones compared with 35.9% of patients with non-calcified stones (p < 0.001). 65.8% of patients with stones measuring more than 30 mm in total diameter required more than three sessions compared with 42.9% of patients with a stone burden less than 30 mm (p < 0.01). At 18-24 (8-12) months follow up, stone clearance was achieved in 94.3% (80.4%) of patients with non-calcified stones, compared with 89.5% (76.8%) in patients with calcified stones and in 75% (71.4%) of patients with a total stone diameter more than 30 mm compared with 95.7% (80.4%) for patients with a total stone diameter less than 30 mm (p < 0.05). ESWL related complications (gross haematuria) occurred in three patients. Thirty six (13.8%) patients experienced biliary colic; four had cholecystectomy, and five endoscopic papillotomy because of common bile duct obstruction. Stone recurrence was seen in 5.3% of patients over a follow up period of up to two years (median 16.6 months).

Brittleness of gallstones to lithotripsy: effect of physicochemical and ultrastructural characteristics

Why some gallstones do not fragment easily to lithotripsy is unclear. The aim of the present study was to determine gallstone factors associated with resistance to fragmentation. Seventy-six cholesterol rich gallstones were subjected to physical evaluation, in vitro computed tomography, chemical analysis by infra red spectroscopy, and ultrastructural studies (of 26 matched stones) by scanning electron microscopy and energy dispersive X-ray microanalysis. In vitro lithotripsy was performed with the Siemens Lithostar Plus machine at a constant energy level. Of 76 stones, 33 required > 1000 shocks for effective fragmentation (largest diameter < or = 5 mm); they had significantly higher maximum diameter (P < 0.001), volume (P < 0.001), weight (P < 0.001) and lower stone density distribution (SDD) index (P < 0.05) and lower calcium bilirubinate content (P < 0.001) than those requiring < or = 1000 shocks. Large (> 15 mm; P < 0.05), round stones (P < 0.02) and gallstones with SDD index of < 50 HU (P < 0.02) and gallstones with SDD index of < 50 HU (P < 0.05) were more difficult to fragment. Clinical application of these parameters may help in better selection of patients for this non-surgical mode of therapy for gallstones.

In vitro study to elucidate the physical laws concerning the fragmentation of both solitary and multiple artificial stones

These in vitro studies define the basic physical laws regarding work and energy for the successful fragmentation of human gallstones. For this purpose a standardized stone model was used consisting of plaster and glass microspheres with physical properties similar to those of human gallstones. All experiments were performed using the lithotripter model MPL9000 (Dornier). The acoustic energy passing stones of 10-30 mm ranged between 8 and 90 mJ per pulse depending on the stone size and energy setting. These results represent the basis for the three following investigations. In the first experiment the relationship between fragmentation and shock wave energy was investigated in a basket with 2 mm mesh size. Thus no layer of small fragments could shadow the acoustic energy for further fragmentation of larger fragments. A constant amount of stone material was found to be fragmented per shock-wave pulse irrespective of stone volume. A low energy threshold (2 mJ/cm3) was observed, below which fragmentation did not occur. In the second experiment, the sieve was covered with a membrane, thus simulating the in vivo situation. The presence of a layer of small fragments hindered the further disintegration of the larger fragments. The attenuation depended to a large extent on original stone volume and acoustic energy per pulse. The corresponding attenuation factor increased with the original stone volume. Thus the fragmentation of a stone with a diameter of 30 mm was attenuated twice as much as a stone of 20 mm size. The critical layer thickness at which no further disintegration took place was 2.5 mm at 18 kV, 4.2 mm at 22 kV, and 5.0 mm at 26 kV.(ABSTRACT TRUNCATED AT 250 WORDS)

Piezoelectric shockwave lithotripters: differences in fragmentation efficiency in vitro

In a comparative assessment of the stone fragmentation efficacy of different piezoelectric lithotripters 72 human gallstones consisting of 24 sets of 3 stones each were disintegrated in vitro using the Piezolith 2300, the EDAP LT.01, and the Therasonic. On the basis of the maximum diameter the calculi were divided into group A (6-15 mm; n = 3 x 16) and group B (16-25 mm; n = 3 x 8) and were treated by using the maximum energy setting of each lithotripter (Piezolith 2300: setting 4, high power; EDAP LT.01: 95%; Therasonic: setting 7). Shockwave application was terminated when the residual fragments measured < or = 4 mm or after a total number of 6000 pulses. With the Piezolith 2300 all calculi could be disintegrated into fragments < or = 4 mm. In contrast, fragmentation was not successful, even after 6000 applied pulses, in the case of 2 and 6 stones when using EDAP LT.01 and the Therasonic lithotripters, respectively. With the remaining concrements of group A (n = 3 x 11) the fragmentation end point was achieved after a lower number of pulses when the Piezolith 2300 (median, 250 pulses; range, 50-500 pulses) was used than with the EDAP LT.01 (1000; 150-2500; p < 0.01) and the Therasonic lithotripters (2750; 750-5500; p < 0.01). Similar results were obtained for group B (n = 3 x 6): the Piezolith 2300 required fewer pulses (200; 100-1250) than the EDAP LT.01 (1000; 500-1000; p < 0.05) and the Therasonic (2000, 500-4000; p < 0.05) units.(ABSTRACT TRUNCATED AT 250 WORDS)

Different modes of fragmenting gallstones in extracorporeal shockwave lithotripsy

Forty radiolucent gallbladder stones from eight patients were fragmented in vitro by extracorporeal shockwave lithotripsy, using the electromagnetic lithotripter Lithostar Plus (Siemens) at five different energy levels. The stones were characterized by size, computed tomography (CT) density, and cholesterol content. The largest residual fragment was measured after every 20 to 100 shock waves. As expected, fewer shock waves were required to achieve fragmentation at higher energy levels. When stones of the same size were compared, there were remarkable differences in the number of shock waves required for fragmentation. These differences must originate in other properties of the stones than size and number. Two different modes of fragmentation were observed: in one group of stones small, flat fragments were chipped off at the beginning of fragmentation ('chipping mode'). These stones initially lost about 25% of their weight as small fragments (< 1 mm) before breaking centrally into some large fragments. In the other group stones initially lost only about 10% of their weight as small fragments (< 1 mm) at the beginning of fragmentation and early broke centrally into some large fragments ('breaking mode'). Stones showing the chipping mode were almost pure cholesterol stones (> 97%) and required significantly less shock waves than stones of the same size showing the breaking mode (cholesterol content, 64-94%). This mode of fragmentation could not be predicted by CT density.

Results of extracorporeal shock wave lithotripsy of gall bladder stones in 693 patients: a plea for restriction to solitary radiolucent stones

During a period of 24 months 693 consecutive patients with symptomatic gall bladder stones (526 males, 167 females; mean age 51 years, range 18-89) were treated by extracorporeal shock wave lithotripsy with a Piezolith 2300. The procedure was carried out on an out-patient basis without analgesics or sedatives. Concomitant chemolitholytic treatment (ursodeoxycholic and chenodeoxycholic acid 7.5 mg/kg/day each) was administered until three months after total fragment clearance for a maximum therapy period of 1.5 years. In 601 patients with radiolucent stones complete clearance of all fragments was obtained after three, six, 12, and 18 months in respectively 20, 41, 64, and 78%. Actuarial analysis of the subgroups according to the stone mass (size and number) selected an ideal patient population with solitary stones less than 20 mm diameter (84% stone free after one year). The results are significantly less good when the greater the number of stones or their maximal diameter increases. Treatment was interrupted in 3.6% of the patients. In 90 sludge or fragments remain present. Twenty five patients were lost to follow up for non-biliary reasons. Stone recurrence was 5.7% at one year and was observed both in patients with solitary and multiple stones. A cost effectiveness analysis suggests that laparoscopic cholecystectomy is the most effective and economic solution, although extracorporeal shock wave lithotripsy for solitary radiolucent stones less than 2 cm is cheaper than conventional cholecystectomy. Extracorporeal shock wave lithotripsy for multiple stones is the most expensive and least effective option.

Gallbladder stones: shockwave therapy

Within the past 7 years, gallbladder lithotripsy by shockwaves has been proven to be a safe and effective non-invasive therapy for selected patients with gallstone disease. While regulatory decisions prevent shockwave therapy from being used more frequently in the USA, the number of patients treated in Europe and Asia is increasing constantly. At our institution, a relatively constant number of about 250 new patients per year have been treated since 1988 (Figure 4). About 20% of patients with gallstones are suitable for shockwave therapy according to present criteria. The rate of evacuation of all fragments is determined by the initial stone number and stone size, the success at stone fragmentation, adjuvant bile acid dissolution therapy, and gallbladder contractility. In contrast to laparoscopic cholecystectomy (Dubois et al, 1989; Perissat et al, 1989; Southern Surgeons Club, 1991), shockwave therapy does not require general anaesthesia. And in contrast to direct contact dissolution therapy of gallbladder stones using MTBE (Thistle et al, 1989), lithotripsy is non-invasive. In the majority of patients, complete fragment disappearance takes several months. Preliminary analyses of the cost-effectiveness of lithotripsy have revealed that lithotripsy, including retreatments and bile acid medication for recurrent stones, costs about as much as open cholecystectomy (Rothschild et al, 1990; Bass et al, 1991). The ideal patient for gallbladder lithotripsy has a single radiolucent stone < or = 20-25 mm in diameter in a functioning gallbladder (Figure 1). In patients with such stones, nearly all studies have confirmed a favourable outcome with rapid clearance of all fragments and a relatively low rate of stone recurrence. For carefully selected patients, extracorporeal shockwave lithotripsy is therefore an attractive non-invasive therapy.

Noninvasive therapy of gallbladder calculi with a radiopaque rim

Safety and efficacy of shock-wave lithotripsy and bile acid dissolution therapy of patients with gallbladder calculi with a radiopaque rim were evaluated. Eighty-six patients with symptomatic solitary stones were treated by this noninvasive therapy and were followed up to 18 months. Three different lithotripsy treatment modalities were used. Up to 1600 shock wave discharges were applied. Patients in group A (n = 20) were treated with an electrohydraulic water-bath lithotripter at a discharge voltage of 18 +/- 1 kV (mean +/- SD), group B patients (n = 25) were treated with an electrohydraulic water-cushion lithotripter at 19 +/- 2 kV, and group C patients were treated (n = 41) with the same lithotripter at 22 +/- 2 kV. Five to eight months after lithotripsy, 15% in group A were free of fragments compared with only 4% in group B (NS vs. group A), and 38% in group C had no stones (NS vs. group A; P = 0.007 vs. B). Thirteen to eighteen months after lithotripsy, the respective results were 59% in group A, 37% in group B (NS vs. group A), and 68% in group C (NS vs. group A; P = 0.05 vs. group B). Patients with fragments of less than or equal to 3 mm in diameter showed significantly better fragment clearance than those with larger fragments. The frequency of adverse effects was not significantly different between the three groups. Biliary colic occurred in 43% of the patients and mild biliary pancreatitis in 3 patients. Endoscopic sphincterotomy was required in 1 patient, and elective cholecystectomy was performed in 6 patients. Using a water-cushion lithotripter at high-power setting, selected patients with solitary gallbladder stones with a radiopaque rim may be treated safely and successfully by shock-wave lithotripsy combined with bile acid dissolution therapy.

Significance of computed tomography for shock-wave therapy of radiolucent gallbladder stones

One hundred eleven symptomatic patients (91 women, 20 men) with solitary "radiolucent" stones (proved by a plain radiograph) underwent examination with computed tomography for stone analysis before extracorporeal shock-wave lithotripsy with a second-generation piezoelectric lithoptripter. The aim of the study was to assess the importance of computed tomography as a diagnostic pretreatment procedure compared with the plain abdominal radiograph: computed tomography density values greater than 50 Hounsfield units (HU) were found in 64 of 111 patients with radiolucent stones (58%). Of these 64, 50 patients even had values greater than 90 HU (50/111;45%). The majority of the stones with density values greater than 50 HU had a hyperdense rim (43 of 64) with a mean maximum attenuation of 134 +/- 68 HU. A significantly higher degree of stone disintegration was achieved with stones of group A (less than or equal to 50 HU) than with those in group B (greater than 50 HU and less than or equal to 90 HU) and group C (greater than 90 HU) with respect to the mean maximum fragment size after the first (P less than 0.001) and last (P less than 0.01) lithotripsy and with respect to the total number of shock waves applied (P less than 0.001) and the number of treatments (P less than 0.001). No difference was observed between groups B and C. After all follow-up periods, the rate of complete stone disappearance was higher in group A than in group B (NS for 1, 2, and 4 months of follow-up; P less than 0.01 for month 8; P less than 0.05 for month 12) and group C (P less than 0.05 for 1, 2, and 4 months of follow-up; P less than 0.001 for months 8 and 12). The authors conclude that computed tomographic analysis of gallstones before lithotripsy is more sensitive in detecting nonradiolucent stones than in the plain radiograph. Computed tomographic stone analysis seems to provide a better selection of patients suitable for biliary lithotripsy and could become a standard diagnostic pretreatment procedure to improve stone disintegration and complete stone disappearance after shock-wave lithotripsy and adjuvant chemolitholysis.

Treatment of gallstones with piezoelectric lithotripsy and oral bile acids. A multicenter study

The efficacy of the combination of piezoelectric lithotripsy and oral bile acids in the treatment of gallbladder stones was assessed. Three hundred and sixty-three patients with symptomatic radiolucent gallstones in functioning gallbladder were treated in five medical centers using the same protocol with the EDAP LT 01 lithotripter. No anesthesia, analgesia or sedation was used. After one session of lithotripsy, fragmentation was observed in 89% of the patients, and satisfactory fragmentation (fragments less than or equal to 5 mm) in 29%. The satisfactory fragmentation rate was higher in patients with solitary stones less than or equal to 20 mm than in patients with solitary stones 21-35 mm or multiple stones (p less than 0.001). After multiple sessions (mean 1.6 session/patient, range 1-5) the overall rate of satisfactory fragmentation was 50%. After 12 months on oral bile acid therapy, complete clearance of the gallbladder was observed in 69% of patients with solitary stones less than or equal to 20 mm, 25% of patients with solitary stones 21-35 mm and 37% of patients with multiple stones. No complication was observed during the lithotripsy. During follow-up under bile acid therapy, there were five complications (1.4%): four patients had acute cholecystitis and one had mild, self-limited pancreatitis. We conclude that piezoelectric lithotripsy with the EDAP lithotripter is a safe and effective treatment which can be performed in outpatients. Satisfactory fragmentation and rapid disappearance of stones are obtained mainly in patients with solitary stones less than or equal to 20 mm.

The effect of ursodiol on the efficacy and safety of extracorporeal shock-wave lithotripsy of gallstones. The Dornier National Biliary Lithotripsy Study

BACKGROUND

In the treatment of gallstones with extracorporeal shock-wave lithotripsy, the bile acid ursodiol is administered to dissolve the gallstone fragments. We designed our study to determine the value of administering this agent.

METHODS

At 10 centers, 600 symptomatic patients with three or fewer radiolucent gallstones 5 to 30 mm in diameter, as visualized by oral cholecystography, were randomly assigned to receive ursodiol or placebo for six months, starting one week before lithotripsy.

RESULTS

The stones were fragmented in 97 percent of all patients, and the fragments were less than or equal to 5 mm in diameter in 46.8 percent. On the basis of an intention-to-treat analysis of all 600 patients, 21 percent receiving ursodiol and 9 percent receiving placebo (P less than 0.0001) had gallbladders that were free of stones after six months. Among those with completely radiolucent solitary stones less than 20 mm in diameter, 35 percent of the patients receiving ursodiol and 18 percent of those receiving placebo (P less than 0.001) were free of stones after six months. Biliary pain, usually mild, occurred in 73 percent of all patients but in only 13 percent of those who were free of stones after three and six months (P less than 0.01). There were few adverse events. Only diarrhea occurred with a significantly different frequency in the two groups: 32.6 percent were affected in the ursodiol group, as compared with 24.7 percent in the placebo group (P less than 0.04). Severe biliary pain occurred in 1.5 percent of all patients, acute cholecystitis in 1.0 percent, and acute pancreatitis in 1.5 percent; endoscopic sphincterotomy was performed in 0.5 percent, and cholecystectomy in 2.5 percent.

CONCLUSIONS

Extracorporeal shock-wave lithotripsy with ursodiol was more effective than lithotripsy alone for the treatment of symptomatic gallstones, and equally safe. Treatment was more effective for solitary than multiple stones, radiolucent than slightly calcified stones, and smaller than larger stones.

Piezoelectric lithotripsy: stone disintegration and follow-up results in patients with symptomatic gallbladder stones

One hundred symptomatic patients with radiolucent gallbladder stones were treated with a new piezoelectric lithotripter and oral chemolitholytic agents. Stone disintegration was achieved in 99 of these patients (99%) with a mean (+/- SD) maximum fragment size of 5.1 +/- 4.1 mm. Significant differences were found when the mean (+/- SD) fragment sizes of single stones less than or equal to 20 mm (4.2 +/- 2.5 mm) were compared with those of single stones greater than 20 mm (5.8 +/- 3.4 mm; P less than 0.05) and multiple stones (6.2 +/- 3.8 mm; P less than 0.05), respectively. None of the patients required anesthesia, analgesics, or sedatives before or during the treatment. The stone-free rates for all patients followed up for up to 4-12 months (mean +/- SD, 10.7 +/- 2.9 months) were 18% (1 month), 25% (2 months), 38% (4 months), 52% (8 months), and 67% (12 months). Partly significant differences were obtained in stone-free rates for single stones (less than or equal to 20 mm) compared with larger stones (greater than 20 mm) and multiple stones (P less than 0.05), respectively. Serious adverse reactions (i.e., cholestasis and pancreatitis) were observed in only 3 patients (3%). These conditions were induced by fragment impaction in the common bile duct. In 2 of these patients, endoscopic retrograde cholangiopancreatography with endoscopic sphincterotomy was required. It is concluded that piezoelectrically generated shock waves are suitable for the effective and safe disintegration of gallbladder stones in humans. The anesthesia-free and analgesia-free shock-wave application opens up the possibility to perform biliary lithotripsy as an outpatient procedure. The stone-free rate achieved in combination with oral bile acids is most promising for single stones (less than or equal to 20 mm).