The Use of Chemical Treatments for Improved Comminution of Artificial Stones

[Mineral-based alkaline waters' prescription in France: Patients are the key point for both nephrologists and urologists]

Alkali therapy is frequently used during chronic kidney disease and nephrolithiasis: nephrologists and urologists are the key operators. Very few is known about the underlying conditions of such a prescription: the aim of this study was to delineate those determinants. We conducted a prospective survey where French nephrologists and urologists were involved. Responders were without gender distinction and principally nephrologists. Prescription frequency was associated with gender (women), specialty (nephrologists), indications and perceived efficiency. Urologists prescribe more often during nephrolithiasis and nephrologists during chronic kidney disease. Urologists were more expert (by scoring on mineral-based alkaline waters compositions knowledge). By multivariate analysis, prescription frequency is associated with gender (women), indications and perceived efficiency by prescribers, which is itself influenced by feedback from patients. These results could have been influenced by a huge representation of nephrologists but foster physicians to go on listening to feedback from patients, due to a lack of clinical trials on the efficiency of mineral-based alkaline waters in such a field. Finally, physicians' education (especially young nephrologists) on mineral-based alkaline waters should be intensified.

In vitro dissolution of calcium oxalate stones with ethylenediaminetetraacetic acid and snake venom thrombin-like enzyme

OBJECTIVE

The aim of this study was to determine the feasibility of using snake venom thrombin-like enzyme (SVTLE) and/or ethylenediaminetetraacetic acid (EDTA) to dissolve calcium oxalate stones in vitro.

METHODS

Seven calcium oxalate stones were incubated with various chemolytic agents [EDTA, Tris-HCl/EDTA (TE) buffer or SVTLE diluted in TE buffer]. The pH, calcium concentration, stone weight and stone surface integrity were recorded, as well as related pathological changes to bladder mucosae.

RESULTS

Compared to all other solutions, those containing SVTLE and buffered EDTA had higher concentrations of mobilized calcium and caused significantly more stone weight loss, stone fragility and gaps in the calcium crystals. Also, there were no adverse pathological effects on rabbit bladder mucosae from any of the solutions.

CONCLUSIONS

The data indicate that buffered EDTA and SVTLE can be used to dissolve calcium oxalate stones and, at the concentrations used here, do not damage tissue.

Chemolysis of calcium oxalate stones: study in vitro and possible clinical application

The flow cell modeling clinical conditions have been used to study the interaction between dilute chemolytic solutions and large calcium oxalate renal stones. The stone treatment with 5% disodium ethylenediaminetetraacetate aqueous solutions or citrate buffer are found not to provide notable disruption of the samples studied. The significant improvement is reached with the mixed compositions containing both natural and synthetic chelating reagents:citrate and ethylenediaminetetraacetate ions as well as an antibiotic. Description of the chemolytic irrigation, numerical results and their possible clinical application are the main topic of the present research.

New concepts in shock wave lithotripsy

This monograph reviews the basic principles of shock wave lithotripsy. The focus is on new research on stone fragmentation and tissue injury and how this improved understanding of shock-wave technology is leading to modifications in lithotripsy that will allow this therapy to be a safer, more effective treatment for nephrolithiasis.

Management of stones in patients with anomalously sited kidneys

PURPOSE OF REVIEW

Congenital abnormities in urology are very common. Horseshoe, malrotated and ectopic kidneys, as well as duplex systems, are the most frequent in this respect. The combination of both abnormalities and stones is of clinical importance. The question is asked if standard procedures for stones apply also to stones in abnormal kidneys.

RECENT FINDINGS

In general, open surgery, extracorporeal shock-wave lithotripsy, percutaneous procedures, endoscopic procedures and laparoscopy are possible procedures in both normal and abnormal kidneys. The importance of ureteric pelvic junction obstruction has to be taken into account and a metabolic work-up remains important.

SUMMARY

The trend for treatment of stones in abnormal kidneys goes towards endoscopical and laparoscopical procedures, whereas a combination of both seems to be appropriate in many cases.

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.

Citrate and vitamin E blunt the shock wave-induced free radical surge in an in vitro cell culture model

Free radical formation plays a major role in shock wave lithotripsy induced renal damage. Moreover, previous studies suggest that free radicals may also promote de novo calcium oxalate crystallization of previously damaged urothelium. Citrate is a known inhibitor of renal stone formation and has also been used as a free radical scavenger. Using an in vitro model with Madin-Darby canine kidney (MDCK) cells, we investigated the influence of two free radical scavengers, citrate and vitamin E, on the prevention of the shock wave-induced free radical surge. Suspensions of MDCK cells were placed in containers for shock wave exposure. Six groups of six containers each were examined: (a) no scavengers 0 shocks, (b) no scavengers 100 shocks, (c) citrate 0 shocks, (d) citrate 100 shocks, (e) vitamin E 0 shocks, (f) vitamin E 100 shocks. An unmodified HM3 was used to deliver 100 shocks at 24 kV. The cell groups that were not shocked acted as the control group and were handled identically, except for the lack of shock wave exposure. After shock wave administration, the containers were emptied and cell suspensions were immediately centrifuged. The supernatant was examined for lactate dehydrogenase (LDH) and 8-isoprostane (8-IP), markers of cellular injury and free radical formation, respectively. Intracellular LDH uniformly increased in all groups exposed to shock wave energy. Similarly, 8-IP increased in all shocked groups. However, the 8-IP increase was significantly reduced when the free radical scavengers were employed. As citrate is a well-known inhibitor of calcium nephrolithiasis, its mechanism of action may be further enhanced, based on its ability to reduce free radical formation, by a protective effect on the urothelium. These data further support the use of citrate based medications during the peri-operative period of shock wave lithotripsy, not only to inhibit stone formation and facilitate fragment passage, but also to reduce the incidence of shock wave induced renal damage. Further studies are warranted to clinically test this hypothesis.

Fatigue of kidney stones with heterogeneous microstructure subjected to shock-wave lithotripsy

In this article a theoretical framework is developed for the mechanics of kidney stones with an isotropic, random microstructure--such as those comprised of cystine or struvite. The approach is based on a micromechanical description of kidney stones comprised of crystals in a binding matrix. Stress concentration functions are developed to determine load sharing of the particle phase and the binding matrix phase. Measurements have shown the inclusions to be considerably harder than the binder; consequently, loading of a stone leads to higher stresses in the inclusions than in the binder. As an illustration of the theory, the fatigue of kidney stones subject to shock-wave lithotripsy is considered. Stress concentration functions are used to construct fatigue-life estimates for each phase, as a function of the volume fraction and of the mechanical properties of the constituents, as well as the loading from SWL. The failure of the binding matrix, or of the particulate phase, is determined explicitly in a model for the accumulation of distributed damage. The theory can be used to assess the importance of microscale heterogeneity on the comminution of renal calculi, and to estimate the number of cycles to failure in terms of measurable material properties.