Influence of alkaline solutions on chemolitholysis and lithotripsy of uric acid stones. An in vitro study

OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of uric acid stones using artificial stones made of uric acid (BON(N)-STONES) which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract the efficacy of different alkaline solutions and artificial urine in dissolving artificial uric acid stones (BON(N)-STONES) was investigated. The dissolution of natural uric acid stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of alkaline solutions, especially THAM at a pH of 10, in dissolving artificial uric acid stones was demonstrated. The investigations on SWL showed a significant improvement on stone comminution of artificial uric acid stones after initial chemolytic treatment with THAM. CONCLUSIONS: New basics to improve dissolution of uric acid stones have been developed by performing standardized in vitro investigations. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of uric acid stones through initial treatment with THAM solution.     

Chemolitholysis and lithotripsy of infectious urinary stones - an in vitro study

OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of infectious urinary stones using artificial stones made of struvite and apatite ('Bon(n) stones') which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract, the efficacy of artificial urine (pH 5.7), Suby G solution (pH 3.6), mixtures of artificial urine with Suby G (pH 3.9 and pH 4.1) in dissolving artificial struvite and apatite stones (Bon(n) stones) was investigated. The dissolution of natural infectious urinary stones was also measured. Additionally, investigations on shock-wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of Suby G solution in dissolving artificial stones was demonstrated. Direct comparison of chemolysis of natural and artificial stones showed no statistical difference between infectious urinary stones and Bon(n) stones of the same material. The investigations on SWL showed a significant improvement on stone comminution, especially of artificial apatite stones after initial chemolytic treatment with Suby G. CONCLUSION: New basics to improve dissolution of infectious urinary stones have been developed by performing standardized in vitro investigations. Local chemolysis with Suby G is an effective tool in the treatment of infectious stone disease. SWL can be improved by varying the physical properties of infectious stones through initial treatment with Suby G solution.     

Chemolysis of struvite stones by acidification of artificial urine--an in vitro study.

OBJECTIVE: The aim of the study was to look for strategies that improve the clinical outcome of struvite stones. An in vitro experimental set up with artificial stones made of struvite (BON(N)-STONES) was chosen to perform standardized and reproducible analyses on various artificial urines with pH-values that may be reached by acidification with oral methionine treatment. MATERIALS AND METHODS: Artificial ball-shaped stones made of struvite (BON(N)-STONES) with a diameter of 0.8 cm were used. The investigations on chemolysis were performed using a dissolution device which simulates the physiological conditions in the upper urinary tract with computer-assisted on line measurement of data. For chemolysis of struvite BON(N)-STONES artificial urines according to Griffith at four different pH-values (pH 5.75, pH 6.0, pH 6.25, pH 6.5) were used. Furthermore natural and struvite BON(N)-STONES were treated with Suby G-solution (pH = 4.0). RESULTS: Comparing natural and artificial struvite stones after treatment with Suby G there was no significant difference regarding their dissolution rate. The dissolution rate of struvite stones in artificial urine rose with a decreasing pH-value. The diminution of the pH-value from 6.5 to 5.75 lead to an increase of the dissolution rate of more than 35%. This increase in the dissolution rate decreased with falling pH-value. CONCLUSIONS: The acidification of urine accelerated the dissolution rate of struvite stones in vitro. Considering in vivo conditions the intake of 1,500-3,000 mg L-methionine may lead to a sufficient acidification for a good dissolution of struvite stones.     

Chemolysis of cystine calculi

Historically, cystine stone chemolysis has been approached with 2 different categories of compounds--alkalizing agents (sodium bicarbonate and tromethamine) and, more recently, protonated thiols and disulfide compounds (alpha-mercaptopropionylglycine, N-acetylcysteine and penicillamine). To establish the relative efficacy of these agents an in vitro model was devised that simulates the clinical setting. The optimal molar concentrations for sodium bicarbonate, N-acetylcysteine and tromethamine were determined initially and then compared at these strengths. Lastly, a variety of solution combinations were made to determine if a synergistic effect could be demonstrated. Results of this study demonstrate that the combination of acetylcysteine, a protonated thiol, with the strong alkalizing agent sodium hydroxide yields the most effective solution for chemolysis of cystine stones. The mechanism of action is believed to occur by a synergistic combination of the pH dependent increase in cystine solubility, with a simultaneously occurring thiol disulfide interchange.     

Practical experiences with antegrade local chemolysis of struvite/apatite, uric acid and cystine calculi in the kidney

In 18 patients (20 kidneys) with struvite/apatite-, uric acid- and cystine stones antegrade local chemolysis was performed via percutaneous or operative nephrostomy. Complete stone dissolution was achieved in 11 kidneys, while in six kidneys partial dissolution of stones was performed. In these six cases added instrumental manipulations shortened the time of therapy. In three cases chemolysis was unsuccessful. Average irrigation time was 21 days per renal unit. Only minor complications like dysuria and skin rashes were seen. Due to long time of irrigation we recommend chemolitholysis mainly as an additional form of therapy in case of residual stones after operative or percutaneous nephrolithotomy.     

Percutaneous catheter dissolution of cystine calculi

In 11 kidneys with presumed cystine stones that were symptomatic and obstructing, percutaneous nephrostomy and stone lavage with either acetylcysteine-bicarbonate solution or tromethamine-E were performed. There were 7 complete stone dissolutions: 2 of 6 attempts with acetylcysteine-bicarbonate alone, 3 of 5 with tromethamine-E, 1 partial with acetylcysteine-bicarbonate, which was completed with tromethamine-E, and 1 proved mixed stone (cystine and calcium phosphate) that required acetylcysteine-bicarbonate and hemiacidrin. In 1 case tromethamine-E irrigation was 97 per cent complete but a few tiny caliceal fragments remained. There were 3 failures of chemolysis: 2 pure cystine stones (1 each acetylcysteine-bicarbonate and tromethamine-E) and 1 mixed calculus with a surface shell of calcium oxalate. Irrigation time was 6 to 42 days for the 7 unoperated kidneys. Tromethamine-E appears to be a more effective agent for cystine stone dissolution. Percutaneous nephrostomy and dissolution are an alternative to an operation in patients with cystine calculous disease.     

In vitro dissolution of cystine urinary calculi

Dissolution of cystine urinary calculi was studied in vitro. Sodium hydroxide, acetylcysteine and tris(hydroxymethyl)aminomethane (tromethamine) were tested for effectiveness in dissolving cystine calculi. Calculi were mounted in a dissolution apparatus. Dissolution rates were calculated from the amount of cystine released into solution per unit time and were compared with linear regression techniques. Calculated dissolution rates of all the irrigating agents tested were similar at a pH of 7.5 and were significantly different at pH 10.0. The most effective agent in the promotion of cystine dissolution was 2 per cent acetylcysteine. Sprague-Dawley rats were used to test the effect of 2 per cent acetylcysteine, 0.3 molar tromethamine and 2 per cent acetylcysteine mixed with 0.3 molar tromethamine on the urothelium. A nephrostomy tube was placed in the left kidney of each rat. The kidneys were irrigated for 3 days with either 2 per cent acetylcysteine, 0.3 molar tromethamine or 2 per cent acetylcysteine mixed with 0.3 molar tromethamine. The rats then were sacrificed at various intervals after infusion. Irrigation with 2 per cent acetylcysteine at a pH of 10 caused an acute inflammatory response at 3 days that was healed almost completely in 4 weeks. The addition of tromethamine to the acetylcysteine did not prevent the inflammatory response.     

Acoustic and mechanical properties of artificial stones in comparison to natural kidney stones

PURPOSE: Standardized and reproducible artificial kidney stone models are important for performing comparative studies of different lithotripsy modalities. The acoustic and mechanical properties of renal calculi dictate the manner by which stones interact with the mechanical stresses produced by shock wave lithotripsy (SWL) or intracorporeal lithotripsy modalities. We have developed a novel artificial kidney stone model that is made of natural substances found in real kidney stones. These stone models appear to be much closer in physical properties to natural kidney stones than previously used stone models. MATERIALS AND METHODS: The acoustic and mechanical properties of six groups of artificial stone models were compared to corresponding natural stones of similar compositions. Moreover, three groups of artificial stone models made of plaster-of-Paris were compared to their natural counterparts. In terms of acoustic properties, stone density was measured using a pycnometer based on Archimedes' principle, whereas longitudinal and transverse (or shear) wave propagation speeds were measured using an ultrasound pulse transmission technique. These values were used to calculate wave impedance and dynamic mechanical properties (bulk modulus, Young's modulus, and shear modulus) of the stones. The microhardness of the stones was measured and the effect of composition on stone fragility was evaluated. RESULTS: Artificial stones, when compared to natural stones of similar composition, showed similar trends in longitudinal and transverse wave speeds, wave impedance, and dynamic elastic moduli. However, values for the artificial stones were uniformly low compared to those of natural stones, suggesting that these artificial stones may be more amenable to shock wave fragmentation. The results of SWL on stone fragmentation of artificial and natural stones also revealed similar trends with the exception of artificial cystine stones which were found to be the most resistant to shock wave fragmentation. CONCLUSIONS: The results indicate that the physical properties of artificial stones made of natural stone materials are comparable to renal calculi of the same chemical composition. The data suggests that these stone phantoms are suitable for performing standardized and reproducible in vitro investigations, especially with regards to fragility of kidney stones of different chemical compositions during SWL.     

Endourological experience with cystine calculi and a treatment algorithm

Between May 1984 and January 1988, 18 patients (31 pyeloureteral units) with documented symptomatic cystine stones were treated. Stone size ranged from 5 to 56 mm. in largest diameter, with an average of 21 mm. All pyeloureteral units were treated initially by endourological methods, including ureteroscopy in 10, percutaneous ultrasonic lithotripsy in 9, extracorporeal shock wave lithotripsy (ESWL) in 10 and chemolysis in 2. Of the patients 10 required a combination of these technologies and 2 required an open operation. Of the 31 units 23 were free of stones when the patient was discharged from the hospital. Of 8 patients with retained stones only 3 had fragments greater than 3 mm. in diameter. Based on this experience an algorithm was developed for the urological management of cystine stones. Ureteral calculi may be removed by ureteroscopic techniques or manipulated into the renal pelvis and managed as renal stones. Cystine renal calculi of less than 1.5 cm. may be treated with ESWL monotherapy. Stones of 1.5 to 3 cm. may be treated with ESWL and dissolution, or percutaneous ultrasonic lithotripsy plus dissolution. Staghorn calculi may be treated by percutaneous ultrasonic lithotripsy plus ESWL and/or dissolution for retained fragments.     

The current role of percutaneous chemolysis in the management of urolithiasis: review and results

The treatment of urolithiasis has changed dramatically over the past several decades. Novel technologies have led to new management protocols. Percutaneous chemolysis as a primary or adjuvant treatment for urinary tract stones has widely been neglected. We present our own experience with it and discuss it in the light of an extensive literature review. From a MEDLINE search on percutaneous chemolysis we evaluated the most important studies, a total of 58 articles, 43 case series and 15 review articles. In our unit between 2001 and 2011, 29 patients (mean age 62 years) with infectious staghorn calculi were treated with adjuvant percutaneous chemolysis post-percutaneous nephrolithotripsy. There were 17 women, with 10 complete and 14 partial staghorn stones (mean size 32 mm). Patients were generally deemed at high risk to undergo another procedure in the future. Suby G solution was used following an established protocol. Sixteen patients (55.1 %) were stone free after chemolysis, eight stones showed partial dissolution, half of them with so-called “insignificant” residual fragments <4 mm. Patients with residual stones underwent SWL. Mean follow-up was 5.25 years (1–11). One stone-free patient (6 %) and three of eight patients (37.5 %) with residual fragments post local chemolysis, developed new stones during follow-up. The often neglected percutaneous chemolysis represents a significant and effective.     

Treatment of cystine urolithiasis by a combination of extracorporeal shock wave lithotripsy and chemolysis

Minimally invasive surgical procedures are particularly desirable in patients with cystine stones because of their often multiple previous operations, complicated stone situations, and high risk of recurrences. Twenty-four treatment episodes for cystine stones were carried out, 12 with extracorporeal shock wave lithotripsy (ESWL) as monotherapy and 12 with a combination of ESWL and percutaneous irrigation with chemolytic solutions. In the ESWL monotherapy group, five of 12 renal units became stone-free and one more patient was discharged stone-free, except for an untreated stone in a calix diverticulum. Combined treatment, most often given in association with more complicated stone situations, rendered seven out of 12 kidneys stone-free. Even in this group, one patient was discharged with an untreated residual stone in a calix diverticulum. Our results show that even complicated cystine stone situations can be successfully treated in a minimally invasive way, with the best results obtained with a combination of ESWL and percutaneous chemolysis. Alkalization of urine seemed to be insufficient in preventing stone formation. No difference in recurrence rate was observed between our two treatment groups.     

Percutaneous chemolysis—An important tool in the treatment of urolithiasis

Persistent residual calculi after therapy, i.e. extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolitholapaxy (PNL), as well as pyelo-and nephrolithotomy are big problems in the treatment of urolithiasis. Furthermore, the therapy of stones is problematic in patients with inadequate drainage, impaired kidney function, or with high risks against anaesthetics. Between 1991 and 1997 percutaneous antegrade chemolysis was carried out in eleven patients. In nine of them complete dissolution of stones was achieved. In two further cases, in which calcium oxalate was the main component of the stoens, chemolysis was unsuccessful. Through our was the main component of the stones, chemolysis was unsuccessful. Through our own cases and under consideration of the literature, we will show that percutaneous chemolysis in these cases is useful and effective in the treatment of urolithiasis.     

Cystine calculi: clinical management and in vitro observations

Although cystine stones account for 1 to 3 per cent of renal calculi, many of these patients are difficult to manage because of recurrent urolithiasis. Seven cases of homozygous cystinuria are summarized. The evolution to the present treatment of percutaneous extraction and chemolysis appears to be the preferred form of treatment although extracorporeal shock wave lithotripsy (ESWL) may also be utilized. In addition, in vitro experiments were conducted to study the effectiveness of different chelating agents and buffers at different urinary pHs. The effect of cystinuric and noncystinuric urines was also evaluated.     

Cystine: a promoter of the growth and aggregation of calcium oxalate crystals in normal undiluted human urine.

PURPOSE: Many variables are known to be associated with the formation of calcium oxalate stones. We noted that on analysis a number of patients with calcium oxalate calculi also had cystine in the stones. Some but not all of these patients showed urinary cystine excretion slightly above the normal limits, resembling heterozygous carriers. This finding raised the question of whether some recurrent stone formers may be at risk for calcium oxalate calculi when they excrete cystine in above normal concentrations. MATERIALS AND METHODS: Pooled urine obtained from 3 pairs of age and sex matched controls was independently analyzed. Each urine sample was divided into spun and filtered, and ultrafiltered urine. A Multisizer II (Coulter Electronics Ltd, Beds, England) was used to measure particle number, diameter and volume. The metastable limit of each specimen was determined. Promotion activity was measured in spun and filtered, and ultrafiltered urine using 3 concentrations of cystine (80, 160 and 320 micromol./l.). Results were confirmed by measuring the incorporation of (14)C-oxalate into the crystals. Scanning electron microscopy was performed to study further the agglomerates as well as exclude cystine crystals. Each experiment was repeated 6 times. Crystalline material was collected for x-ray powder diffraction analysis. RESULTS: The urine metastable limit did not change with increasing cystine concentrations. Particle diameter increased significantly from 10.6 microm in ultrafiltered urine alone to 11.6 and 13.5 microm (p < 0.05) at 160 and 320 micromol/l. cystine, respectively. In addition, particle volume also increased proportionally in a dose response manner to cystine concentration. The dose of 320 micromol/l. cystine increased the crystal growth rate 52%. 14C-oxalate experiments confirmed these results. Scanning electron microscopy at 500x magnification revealed no cystine crystals in any experiments performed. Furthermore, x-ray powder diffraction analysis of samples revealed that experimentally determined parameters matched reference values for calcium oxalate trihydrate but not for cystine, again confirming absent cystine in the samples. CONCLUSIONS: Adding cystine to undiluted human urine resulted in the marked enhancement of calcium oxalate crystal precipitation. When considered with the finding of cystine in calcium oxalate stones in the noncystinuric population, this result implies that urinary cystine may be a risk factor for calcium oxalate calculi. Cystine was not observed in any calcium oxalate crystals, suggesting that the mechanism of crystal formation was a salting out effect.     

Effects of inositol hexaphosphate (phytate) on calcium binding, calcium oxalate crystallization and in vitro stone growth

PURPOSE: We measured and compared 3 activities of inositol hexaphosphate, also known as phytate, to explore their importance in relation to antilithogenic potential. MATERIALS AND METHODS: Calcium binding activity by inositol hexaphosphate was measured with a calcium electrode in artificial and whole urine. Calcium oxalate crystallization inhibition was measured by a 96-well plate turbidimetric method with artificial and whole urine. Effects on stone growth were measured in an in vitro system of 12 stones grown simultaneously (a stone farm) using artificial urine alone or supplemented with urinary macromolecules. RESULTS: Phytate decreased ionized calcium, increased the metastable limit, decreased the crystallization turbidity rate index and decreased the in vitro stone growth rate. The effective concentration for calcium binding reduction was about 2 orders of magnitude higher than that required for crystallization inhibition, which in turn was about 2 orders of magnitude higher than that required for stone growth inhibition. When human urine or artificial urine supplemented with urinary macromolecules was used, the effective concentration of phytate for inhibiting crystallization and stone growth was increased by about 1 order of magnitude. CONCLUSIONS: Inhibition of crystallization by phytate does not depend on decreasing the effective ionized calcium concentration and inhibition of in vitro stone growth does not depend on inhibiting crystallization of the suspended crystals. To our knowledge this is the first demonstration of a quantitative distinction between the inhibition of crystallization and stone growth. Inhibition of in vitro stone growth in the presence of macromolecules occurred at concentrations consistent with urinary phytate excretion.     

Experimental studies and first clinical experience with a new Lithoclast and ultrasound combination for lithotripsy

OBJECTIVES: A new lithotriptor for intracorporeal lithotripsy was developed combining the two most effective lithotriptors. A combination of the mechanically driven Lithoclast Master and a new ultrasonic device was constructed. Efficacy was tested in standardized model stones and in patient treatment. MATERIAL: The new lithotriptor is composed of a Lithoclast Master and an ultrasonic device (EMS, Nyon, Switzerland). The 1.0 mm Lithoclast probe is advanced off-center through the hollow 3.3 mm ultrasonic probe and protrudes about 1 mm. Five different artificial stones of defined hardness and density were used as model stones for disintegration. Time until first fragmentation and complete fragmentation (particles smaller than 2.2 mm to fit through the ultrasonic probe), percent disintegration after 1 min and time until 50% disintegration were determined for the new device as well as lithoclast and ultrasound alone. A total of 68 patients were treated by percutaneous nephrolitholapaxy (PNL) with the new device from February 1999 to August 2001. Lithotripsy was performed after fluoroscopically guided puncture of the lower calix and dilatation of the nephrostomy tract with coaxial bougies. Thirty-five patients had complete and 33 patients partial staghorn calculi. RESULTS: First fragmentation was reached 25-200 times faster with the combination as with either mode alone. Disintegrated stone mass after 1 min was 1.5-4 times larger in combined lithotripsy and 50% disintegration time 30-50% shorter. Clinically, complete stone free rate (KUB and ultrasound) was 66% after the first PNL. Sixteen out of 68 patients had a second look PNL with an overall stone free rate of 89.7% by dismission. Stone composition was calcium-oxalate-monohydrate in 13%, Ca-ox-monohydrate/uric acid in 35%, apatite in 20% and cystine in 11%. CONCLUSION: In in vitro experiments and clinically the new lithotriptor provides easy handling and high effectivity in fragmentation of all stones regardless of their composition.     

Experience with percutaneous nephrostomy, extracorporeal shock wave lithotripsy and chemolysis in the treatment of obstructive uric acid stones.

Intravenous pyelography (IVP), retrograde ureteral catheterization and percutaneous nephrostomy (PCN) have been used to locate radiolucent stones during ESWL in an X-ray localization system lithotripter. We also used an alternative method combining PCN, ESWL and chemolysis to treat 8 obstructive uric acid stones. The average number of shock wave pulses was 1,725 (range 1,000-2,000), the generator voltage of the HM-3 Dornier lithotripter was 20-22 kV, and the local chemolysis lasted 4 days (range 2-7). All radiolucent uric acid stones were successfully disintegrated. Of the 8 patients treated, 5 were completely free of stones and the other 3 had insignificant residual stones after 3 months. Three patients who developed fever during local chemolysis with 0.1 M sodium bicarbonate solution were managed conservatively without severe sequelae. Only 1 patient retained a PCN tube after discharge. Because PCN can provide a path for local chemolysis and better localization, it is especially helpful in treating obstructive uric acid stones.     

Clinical experience of extracorporeal shock wave lithotripsy for cystine calculi

Thirty patients (16 men and 14 women) with cystine urinary stones were treated by extracorporeal shock wave lithotripsy (Dormer HM-3) from December 1984 through October 1989. The average patient age was 35.2 years with a range of 14 to 59 years. Seventy per cent of these subjects had had previous open surgical operations for stones. The cases consisted of 7 ureteral stones and 37 renal stones, including 15 staghorn calculi. An average of 1.3 session of ESWL was carried out to treat ureteral stones. Thirty-seven renal units with renal stone required 96 sessions of lithotripsy (average 2.6 sessions per unit). Seven patients with ureteral stones required auxiliary procedures, i.e., one transurethral lithotripsy (TUL), two percutaneous nephrostomies (PNS) and one open surgery. Thirty-seven renal stones, including staghorn calculi was treated by ESWL and auxiliary treatment of 21 TUL procedures, one PNS, 16 PNL procedures and one chemical chemolysis. Successful fragmentation (residual debris less than or equal to 4 mm) was achieved in 85.7% of ureteral stones, 90.9% of renal stones and 73.3% of staghorn calculi. The stone free rates of patients with ureteral stones, renal stones and staghorn calculi were 71.4%, 50.0% and 53.5%, respectively, at 3 months after ESWL. No serious complications were seen in this series. Fever above 38.5 degrees C was the most common complications (13.5%). Ureteral perforation was encountered once in TUL procedures. Transfusion and selective arterial embolization were needed for one case treated by PNL procedures. Although cystine stone is harder to be fragmented by ESWL than other stone composition, ESWL and endourology may be effective and safe procedures for cystine stone patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Infrared spectroscopic analysis of urinary stones (including stones induced by melamine-contaminated milk powder) in 189 Chinese children

Aim

The aim of the study was to investigate the composition of the stones in Chinese children with urolithiasis, including peculiar stones induced by melamine-contaminated milk powder.

Materials and Methods

Between 1999 and 2009, 189 urinary stones from children of East China were received at our institution. Among them, 12 stones were received from pediatric stone formers with a history of consuming melamine-contaminated milk powder in 2008; and the remaining stones were defined as “natural” stones. All stones were analyzed by Fourier transform infrared spectroscopy.

Results

Among 177 “natural” stones, whewellite stone (49.72%) was observed most frequently followed by weddellite stone (15.25%), uric acid anhydrous stone (9.6%), carbapatite stone (9.04%), cystine stone (9.04%), ammonium acid urate stone (4.52%), struvite stone (2.26%), and sodium urate stone (0.56%). Twelve young children who consumed melamine-contaminated milk powder were younger than 3 years, and their stones were composed of a mixture of uric acid dihydrate and ammonium acid urate based on Fourier transform infrared spectroscopy. In addition, the stones were radiolucent and could be dissolved by urine alkalinization.

Conclusions

Our study emphasizes the relatively high rate of calcium oxalate stones and cystine stones, and the relatively low rate of struvite stones in Chinese children with urolithiasis. The stones caused by melamine-contaminated milk powder are composed of the mixture of uric acid dihydrate and ammonium acid urate.     

How to improve lithotripsy and chemolitholysis of brushite-stones: an in vitro study

Because of their resistance to fragmentation, treatment of brushite stones is a big problem. This study was performed to look for an improvement in therapeutic strategies by using artificial stones made of brushite (Bon(n)-stones), which are comparable to their natural counterparts. Using an ultrasound transmission technique, longitudinal wave propagation speeds were measured at different time intervals during treatment with hemiacidrin. From these and density measurements, transverse wave speed, wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of artificial stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of brushite stones through treatment with hemiacidrin. Additionally, we demonstrated the efficacy of Suby G in dissolving artificial brushite stones using an experimental arrangement simulating the physiological conditions in the upper urinary tract. Moreover, the efficacy of four different intracorporeal lithotripsy devices (electrohydraulic, pneumatic, laser and ultrasound) was tested and it was shown that electrohydraulic lithotripsy seems to be the best system for comminution of brushite stones. Received: 7 September 1998 / Accepted: 10 February 1999