Ultracal-30 gypsum artificial stones for research on the mechanisms of stone breakage in shock wave lithotripsy

Artificial stones are used in research on the mechanisms of stone breakage in shock wave lithotripsy (SWL) and in assessing lithotripter performance. We have adopted Ultracal-30 gypsum as a model, finding it suitable for SWL studies in vitro, acute animal experiments in which stones are implanted in the kidney, and as a target to compare the in vitro performance of intracorporeal lithotripters. Here we describe the preparation of U-30 stones, their material properties, shock wave (SW) breakage characteristics, and methods used for quantitation of stone fragmentation with this model. Ultracal-30 gypsum cement was mixed 1:1 with water, cast in plastic multi-well plates, then, the stones were liberated by dissolving the plastic with chloroform and stored under water. Stone breakage in SWL was assessed by several methods including measures of the increase in projected surface area of SW-treated stones. Breakage of hydrated stones showed a linear increase in fragment area with increased SW-number and SW-voltage. Stones stored in water for an extended time showed reduced fragility. Dried stones could be rehydrated so that breakage was not different from stones that had never been dry, but stones rehydrated for less than 96 h showed increased fragility to SWs. The physical properties of U-30 stones place them in the range reported for natural stones. U-30 stones in vitro and in vivo showed equivalent response to SW-rate, with ~200% greater fragmentation at 30 SW/min compared to 120 SW/min, suggesting that the mechanisms of SW action are similar under both conditions. U-30 stones provide a convenient, reproducible model for SWL research.     

Effect of potassium citrate therapy on stone recurrence and residual fragments after shockwave lithotripsy in lower caliceal calcium oxalate urolithiasis: a randomized controlled trial

BACKGROUND AND PURPOSE: To evaluate the efficacy of potassium citrate treatment in preventing stone recurrences and residual fragments after shockwave lithotripsy (SWL) for lower pole calcium oxalate urolithiasis. PATIENTS AND METHODS: One hundred ten patients who underwent SWL because of lower caliceal stones and who were stone free or who had residual stone 4 weeks later were enrolled in the study. The average patient age was 41.7 years. All patients had documented simple calcium oxalate lithiasis without urinary tract infection and with normal renal morphology and function. Four weeks after SWL, patients who were stone free (N = 56) and patients who had residual stones (N = 34) were independently randomized into two subgroups that were matched for sex, age, and urinary values of citrate, calcium, and uric acid. One group was given oral potassium citrate 60 mEq per day, and the other group served as controls. RESULTS: In patients who were stone free after SWL and receiving medical treatment, the stone recurrence rate at 12 months was 0 whereas untreated patients showed a 28.5% stone recurrence rate (P < 0.05). Similarly, in the residual fragment group, the medically treated patients had a significantly greater remission rate than the untreated patients (44.5 v 12.5%; P < 0.05). CONCLUSION: Potassium citrate therapy significantly alleviated calcium oxalate stone activity after SWL for lower pole stones in patients who were stone free. An important observation was the beneficial effect of medical treatment on stone activity after SWL among patients with residual calculi.     

Prognostic variables for shockwave lithotripsy (SWL) treatment success: no impact of body mass index (BMI) using a third generation lithotripter

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? Therapy success in SWL treatment differs between individuals. According to recent studies done with first and second generation lithotripters, different prognostic variables like stone size, stone location, stone composition, age of patient and BMI have been shown to have prognostic relevance for outcome after SWL treatment. This study has been performed with a newer, third generation lithotripter. According to this study, BMI has no impact on SWL treatment success. Therefore, SWL treatment with newer generation lithotripters should be considered for the treatment of kidney stones in overweight and obese patients.

OBJECTIVE

? To investigate the effect of different variables including body mass index (BMI) on therapy outcome in patients with upper urinary tract stones treated with a third generation lithotripter, as BMI has been reported to be an independent predictor for stone‐free status after extracorporeal shockwave lithotripsy (SWL) performed with first or second generation lithotripters.

PATIENTS AND METHODS

? In all, 172 patients with kidney stones with a mean (range) size of 9.2 (3.0–32.0) mm were included in the study. ? In all, 91 patients (52.9%) were treated with a ureteric stent in situ. ? For SWL therapy a third generation, electromagnetic lithotripter (Siemens Lithoskop^TM) was used. Stone‐free status was reached, when no more treatable stones were present (no stone or stone < 3 mm). ? BMI, stone size and localization, age, gender, treatment parameters and ureteric stent in situ were evaluated for their prognostic relevance on therapy success.

RESULTS

? The mean (range) BMI of all patients was 27.8 (19.0–58.6) kg/m². ? Patients were categorized into two groups: A) patients that were stone free after one treatment; B) patients with residual stones. The mean (sd ) BMI was 27.4 (4.6) kg/m² and 28.4 (6.1) kg/m² for A and B, respectively. ? Univariate and multivariate analysis for freedom of stones showed that only stone size (P < 0.01) and presence of a ureteric stent (P= 0.01) were independent prognostic variables. ? BMI had no significant influence on therapy outcome (P= 0.51).

CONCLUSIONS

? Using a third generation lithotripter, BMI was not an independent predictor of stone‐free rate after SWL therapy of kidney stones. ? This effect might be attributed to a greater penetration depth of the shockwave energy. Stone size and a ureteric stent in situ were the only variables with prognostic significance.     

Management of lower pole renal calculi: shock wave lithotripsy versus percutaneous nephrolithotomy versus flexible ureteroscopy

Current ureteroscopic intracorporeal lithotripsy devices and stone retrieval technology allow for the treatment of calculi located throughout the intra-renal collecting system. Difficulty accessing lower pole calculi, especially when the holmium laser fiber is utilized, is often encountered. Herein we review our experience where lower pole renal calculi were ureteroscopically managed by holmium laser fragmentation, either in situ, or by first displacing the stone into a less dependent position with the aid of a nitinol stone retrieval device. Lower pole stones less than 20 mm can be primarily treated by ureteroscopic means in patients: that are obese; have a bleeding diathesis; with stones resistant to shockwave lithotripsy (SWL); with complicated intra-renal anatomy; or as a salvage procedure after failed SWL. Lower pole calculi are fragmented with a 200 μm holmium laser fiber via a 7.5 F flexible ureteroscope. For those patients where the laser fiber reduced ureteroscopic deflection, precluding re-entry into the lower pole calyx, a 1.9 F nitinol basket is used to displace the lower pole calculus into a more favorable position, thus allowing for easier fragmentation. A nitinol device passed into the lower pole, through the ureteroscope, for stone displacement cause only a minimal loss of deflection and no significant impact on irrigation. Eighty-five percent of patients were stone free by IVP or CT scan performed at 3 months. Ureteroscopic management of lower pole calculi is a reasonable alternative to SWL or percutaneous nephrolithotomy (PNL) in patients with low volume stone disease. If the stone cannot be fragmented in situ, nitinol basket or grasper retrieval, through a fully deflected ureteroscope, allows for repositioning of the stone into a less dependant position, thus facilitating stone fragmentation.     

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.     

Is there a simpler method for predicting lower pole stone clearance after shockwave lithotripsy than measuring infundibulopelvic angle?

BACKGROUND AND PURPOSE: Several anatomic factors influence the clearance of lower pole stones treated with shockwave lithotripsy (SWL). One of these is the infundibulopelvic angle, but its measurement is complex. METHODS: We proposed a more simple measure of caliceal dependence, the caliceal pelvic height (CPH), which we defined as the distance between a horizontal line from the lowermost point of the calix containing the stone to the highest point of the lower lip of the renal pelvis. RESULTS: In 62 patients who had SWL for solitary lower pole stones, a CPH < 15 mm was associated with a stone clearance rate of 92%, whereas with a CPH > or = 15 mm, the clearance rate was only 52% (p < 0.05). A majority (74%) of the patients with an infundibular width of > or = 5 mm were rendered stone free compared with 40% of those with a width of < 5 mm (p < 0.05). CONCLUSION: Measurement of the CPH, in conjunction with other anatomic factors, may more accurately predict the outcome of SWL in patients with lower pole stones.     

Synchronous twin-pulse technique to improve efficacy of SWL: preliminary results of an experimental study.

BACKGROUND AND PURPOSE: Extracorporeal shockwave lithotripsy (SWL) is the treatment of choice for the majority of renal and ureteral stones. The Dornier HM3 lithotripter has good results but with some limitations and complications. A number of second- and third-generation machines have been developed employing different energy sources, focusing devices, and coupling media. These devices overcome some of the limitations and lessen the complications but at the expense of the success rate. Use of the consecutive double-pulse technique (as in the MFL 5000) and of combined under-table and over-table modules consecutively (as in the Siemens Lithostar Plus) improves the efficacy of fragmentation. The aim of this study was to study the effects of the use of synchronous twin pulses generated by under-table and over-table identical shockwave reflectors for stone fragmentation. MATERIALS AND METHODS: We designed a lithotripter with two identical shockwave generators and identical reflectors (twin heads). One reflector was under the table and fixed, while the second reflector was over the table and hangs on a C-arm so that the angle between the axes of the two reflectors could be changed. The second focal points (F2) of the two reflectors lay in the same position. A lucent lightweight acrylic water tank with one side sealed by a silicon rubber membrane was fixed to the SWL table so that the membrane coupled with the water cushions of both reflectors. The tank was filled with degassed water and the targeted material was fixed on a holder and immersed in the water so as to be at F2. Comparison of the use of one shockwave source and two shockwave sources simultaneously was done relative to: (1) cavitation effect on aluminum foil; (2) quality of disintegration, shape of the focal zone, and ideal position of F2 using ceramic blocks; and (3) disintegrative efficacy using dental bone cement. RESULTS: The cavitation effect became more localized with the use of two reflectors. Also, the volume and rate of stone disintegration increased with the use of the two reflectors, with production of fine (<2-mm) fragments. The focal zone became smaller and conical with no propagation of shockwaves beyond F2. These results were more evident if the angle between the axes of the reflectors was 90 degrees. CONCLUSION: This new technique of SWL may improve the efficacy of treatment of urinary tract stones. It also may be less harmful to the renal tissues, but animal experiments must be carried out to prove this.     

Prefocal alignment improves stone comminution in shockwave lithotripsy

BACKGROUND: The Dornier HM-3 machine continues to be one of the most effective lithotripters in use. However, tissue damage occurs in most, if not all, shockwave lithotripsy (SWL) treatments. Cavitation appears to contribute to desired stone comminution as well as to undesired tissue damage. Studies of cavitation in electrohydraulic shockwave lithotripters indicate that the greatest cavitation activity occurs, not at the geometric focus, F2, but at a site proximal to F2 by 1 to 3 cm. In clinical practice, however, stones are aligned with F2. MATERIALS AND METHODS: In vitro stone comminution, hemolysis, and free-radical production were assessed along the focal axis, and pig kidneys treated with SWL in vivo were sectioned to determine the extent of hemorrhagic injury along the focal axis. Model gypsum stones received 200 shockwaves in vitro at 18 kV. RESULTS: At F2, the average number of fragments >1.5 mm was 1.3 +/- 0.5, and the weight loss was 11.3 +/- 1.1%. At 2 cm from F2 (F2-2 cm), these values increased to 4 +/- 2.8 and 16.1 +/- 4.2%, respectively. Samples of 10% hematocrit blood were similarly exposed. Hemolysis was equivalent at F2-2 cm (14.7 +/- 2.3%) and F2 (15.2 +/- 3%) but decreased significantly at all other positions. Samples of iodine solution received 1500 shockwaves at 20 kV. Hydroxyl radical production was greatest at F2-2 cm (0.384 +/- 0.035 microM) and decreased significantly distal to this position. The volume of tissue injury in pig kidneys was greatest with prefocal shockwave exposure. CONCLUSION: Stone comminution may be achieved more rapidly without greater tissue damage by a simple shift in stone alignment to F2-2 cm.     

Piezoelectric shockwave lithotripsy of urinary calculi: comparative study of stone depth in kidney and ureter treatments

PURPOSE: The aim of this prospective study was to assess the relation between stone depth and the efficiency of piezoelectric extracorporeal shockwave lithotripsy (SWL). PATIENTS AND METHODS: A total of 150 patients presenting with 25 pelvic, 75 caliceal, and 25 upper and 25 lower ureteral calculi were treated using the EDAP LT02 lithotripter. All of the stones were easy to localize with sonographic and radiographic systems, and their largest diameter ranged from 4 to 25 mm (mean 8.5 mm). Renal and upper ureteral calculi were treated with the patient in the supine position and lower ureteral stones in prone position. On the basis of a meticulous stone localization and focusing, depth measurements were carried out under real-time ultrasonic guidance, the minimal distance between the cutaneous plane and the focal point being recorded only for definitely localized calculi. RESULTS: Ureteral calculi were significantly deeper than renal stones (p < 0.0001), but the distance from the cutaneous plane was statistically similar for upper and lower ureteral calculi. Stone depth was statistically affected by body mass index (BMI), patients with a BMI >25 having significantly deeper renal and ureteral calculi than subjects with a BMI < or =25 (p < 0.00001 and 0.01, respectively). Renal stones resisting SWL were significantly deeper than successfully treated calculi (p < 0.03). At the level of the ureter, the success rate after one SWL session was 85% for stones with a depth < or =110 mm and 57% for deeper stones, the difference being significant (p < 0.05). CONCLUSION: Stone depth has a significant influence on treatment outcome after piezoelectric SWL for both renal and ureteral calculi. We recommend particular attention be given to corpulent patients presenting with ureteral stones.     

Is measurement of stone surface area necessary for SWL treatment of nonstaghorn calculi?

BACKGROUND AND PURPOSE: The size of urinary tract stones is usually assessed by the longest diameter (LD) alone. Logically, however, two-dimensional measurement of the stone surface area (SSA) susceptible to shockwaves would give more useful information for the planning of treatment by extracorporeal shockwave lithotripsy (SWL). This has been shown for staghorn calculi. The aim of this study was to determine for nonstaghorn kidney and ureter stones whether the LD alone identifies as reliably a subgroup of patients with a stone of a certain size as does the SSA. Furthermore, we sought to determine whether the LD alone indicates as reliably the number of patients who would be rendered stone free after one SWL session within a certain subgroup as would the SSA. PATIENTS AND METHODS: Retrospectively, SWL treatment and radiographic data of 330 patients who had undergone SWL for a single stone were analyzed. RESULTS: Ureteral stones were significantly smaller on average, and ureteral stone patients needed fewer SWL treatment sessions and fewer shockwaves to become stone free. Stratification of both kidney and ureteral stones by either LD or SSA resulted in comparable groups of patients. There were no significant differences in patient, stone, or treatment data. More importantly, the stone-free rates after one treatment did not differ significantly. CONCLUSION: The LD does accurately reflect the size of a nonstaghorn kidney or ureteral stones. Therefore, the measurement of LD, as generally practiced, appears clinically sufficient and appropriate for the assessment of stone size prior to SWL in both kidney and ureteral stones.     

Why stones break better at slow shockwave rates than at fast rates: in vitro study with a research electrohydraulic lithotripter

BACKGROUND AND PURPOSE: Stones break better when the rate of shockwave (SW) delivery is slowed. It has been hypothesized that the greater cavitation accompanying a fast rate shields pulse propagation, thus interfering with the delivery of SW energy to the stone. We tested this idea by correlating waveforms measured at the SW focus with cavitation viewed using high-speed imaging. MATERIALS AND METHODS: A series of U30 gypsum stones held in a 2-mm mesh basket were exposed to 200 SWs at 30 or 120 SW/min from a research electrohydraulic lithotripter (HM3 clone). Waveforms were collected using a fiberoptic probe hydrophone. High-speed imaging was used to observe cavitation bubbles in the water and at the stone surface. Results: Stone breakage was significantly better at 30 SW/min than at 120 SW/min. The rate had little effect on SW parameters in the water free field. In the presence of particulates released from stones, the positive pressure of the SW remained unaffected, but the trailing tensile phase of the pulse was significantly reduced at 120 SW/min. CONCLUSIONS: Cavitation bubbles do not persist between SWs. Thus, mature bubbles from one pulse do not interfere with the next pulse, even at 120 SW/min. However, cavitation nuclei carried by fine particles released from stones can persist between pulses. These nuclei have little effect on the compressive wave but seed cavitation under the influence of the tensile wave. Bubble growth draws energy from the negative-pressure phase of the SW, reducing its amplitude. This likely affects the dynamics of cavitation bubble clusters at the stone surface, reducing the effectiveness of bubble action in stone comminution.     

10-year experience with extracorporeal shockwave lithotripsy in the state of Colorado

PURPOSE: To evaluate trends in the utilization of extracorporeal shockwave lithotripsy (SWL) and the potential need for medical prophylaxis of urolithaisis in the state of Colorado. MATERIALS AND METHODS: We examined patient and stone characteristics of individuals undergoing SWL for renal or upper-ureteral stones over a 10-year period (1987-1996) at the Kidney Stone Center of the Rocky Mountains. There were no significant changes in the in-state physician referral patterns nor SWL treatment criteria over this time interval. All patients were treated on the Dornier HM3 lithotripter. From September 1999 to December 1999, 198 consecutive patients undergoing SWL filled out a 10-point questionnaire regarding their interest in medical prophylaxis of urolithiasis. RESULTS: The number of patients from Colorado rose 32.5%: from 15.7 per 100,000 population in 1987 to 20.8 per 100,000 in 1996. Patient demographics such as sex, race, age, and history of nephrolithiasis did not change. Furthermore, there were no significant changes in the treated stone size or stone location. The overall increase in treatment numbers was attributable equally to increases in the number of upper ureteral and renal stones. Of the 198 patients questioned, 114 (58%) were recurrent stone formers, but only 52 (45%) of these had been offered a metabolic evaluation. CONCLUSIONS: Over the 10 years since the introduction of WSL in Colorado, there has been a gradual increase in its utilization. This higher utilization is probably multifactorial. Patients undergoing SWL have a strong desire to prevent future stone episodes and are very interested in medical prophylaxis of their stone disease.     

Effect of potassium citrate therapy on stone recurrence and regrowth after extracorporeal shockwave lithotripsy in children

BACKGROUND AND PURPOSE: Stone disease in children may cause functional and morphologic changes in the urinary tract during longer-term follow-up. Prevention of stone recurrence will be possible only with careful metabolic evaluation and appropriate management. The possible preventive effects of potassium citrate therapy on true stone recurrence, as well as regrowth rates after shockwave lithotripsy (SWL), were evaluated in children treated for renal stones. PATIENTS AND METHODS: Following assessment of the efficacy of SWL, 96 children (72 male, 53 female aged 4 to 14 years with a mean of 6.6 years) were evaluated for the effects of potassium citrate on residual fragments as well as true new stone formation during long-term follow-up. All children had calcium-containing stones with normal renal morphology and function without any urinary-tract infection. Depending on the outcome of treatment, patients with and without residual stones were allocated independently to Group I (N = 52) and Group II (N = 44), which were matched for sex and age. Group I was given oral potassium citrate 1 mEq/kg daily for 12 months; the remaining children served as controls. Follow-up ranged from 12 to 36.6 months, with a mean of 24.4 months. Follow-up results for at least a year with respect to the stone recurrence or stone growth rates were recorded in both groups. RESULTS: Stone-free children undergoing no specific therapy had significant new stone formation compared with the group receiving potassium citrate on a regular basis (34.6% and 7.6%, respectively). Children with residual fragments receiving no specific preventive measure also showed significant new stone formation, along with enlargement of the fragments. CONCLUSION: In addition to stone removal, treatment of pediatric urolithiasis requires a thorough metabolic evaluation. Depending on the abnormalities, each patient should be advised on adequate drinking to increase the urine volume in accordance with body size. Although children with hypocitraturia may well benefit from therapeutic agents that raise the urine citrate concentration, our results did clearly show that all children bearing residual fragments should be counseled on adequate fluid intake along potassium citrate treatment to prevent stone regrowth or formation during long-term follow-up.     

Significance of lower-pole pelvicaliceal anatomy on stone clearance after shockwave lithotripsy in nonobstructive isolated renal pelvic stones

PURPOSE: To investigate the probable effect of lower-pole pelvicaliceal anatomy on stone clearance after shockwave lithotripsy (SWL) in patients with nonobstructive renal pelvic stones. PATIENTS AND METHODS: The clinical records of patients with isolated renal pelvic stones who underwent SWL between 1996 and 2005 were reviewed. After excluding patients with obstruction leading to dilatation, major anatomic abnormalities, noncalcium stones, metabolic abnormalities, history of recurrent stone disease, multiple stones, and previous renal surgery, 153 patients were enrolled in the study. Lower pole infundibulopelvic angle (IPA) and infundibular length and width were measured from intravenous urography. Patients were classified into three groups according to stone burden (group 1, <100 mm(2); group 2, 101-200 mm(2); group 3, 201-400 mm(2)). RESULTS: The mean stone size was 142.08+/-86.3 mm(2). Overall stone-free rate was 53.6%. Localization of clinically significant or insignificant residual fragments was in the lower calix, renal pelvis, and both in 50 (32.6%), 29 (18.9%), and 8 (5.2%) patients, respectively. There was no statistically significant difference in pelvicaliceal anatomic features except narrower IPA (P=0.02) in group 1 patients with residual stones. CONCLUSION: The falling of stone fragments to the lower calix in spite of the ureter whether clinically significant or not after SWL of pelvic stones initially seems to be related to stone burden rather than lower caliceal anatomy. However, existence of a more narrow IPA in group 1 patients with residual fragments led us to believe that lower-pole IPA can play a role in stone clearance, especially for smaller stones, probably because of smaller residual fragment size or the more mobile nature of the primary stone.     

Is intravenous urography a prerequisite for renal shockwave lithotripsy?

PURPOSE: To determine whether intravenous urography (IVU) is a prerequisite for shockwave lithotripsy (SWL) of renal stones by addressing whether using non-contrast-enhanced CT (NCCT) instead of IVU for delineating urinary tract anatomy is associated with post-SWL complications. PATIENTS AND METHODS: Thirty-eight patients treated by SWL (Econolith 2000) for radiopaque renal stones underwent either IVU or NCCT. Twenty patients with normal urinary tracts or with mild hydronephrosis proximal to the stone on urography comprised the IVU group. Eighteen patients who underwent NCCT and plain abdominal (KUB) films and had urinary tract systems similar in appearance to the IVU group comprised the NCCT group. The two groups were of similar mean age (45.75 years, range 24-73 years; and 49.0 years, range 26-72 years, respectively) and had a similar mean stone size (10.1-10.2 mm). Patients with internal ureteral or nephrostomy catheters were excluded. Information on episodes of intractable renal colic, urinary tract infections, and hospitalization was recorded at follow-up 2 to 6 weeks post-SWL. RESULTS: The IVU and NCCT patients had similar mean stone fragmentation rates (80% and 74%, respectively) at 2 to 6 weeks post-SWL. Four IVU patients (20%) had intractable renal colic. One NCCT patient (5.5%) had a urinary infection. Complication and hospitalization rates in the two groups were not significantly different (P = 0.34; Fisher' exact test). CONCLUSIONS: Using only NCCT before SWL was not associated with higher complication rates. Thus, IVU is not a prerequisite for SWL of radiopaque renal stones in patients with a normal urinary tract anatomy as seen on NCCT.     

Extracorporeal shockwave lithotripsy compared with ureteroscopy for the removal of small distal ureteral stones

INTRODUCTION: The treatment of small distal ureteral stones smaller or equal to 5 mm in size is still highly controversial. In distal ureteral stones larger than 5 mm in size, ureteroscopy (URS) has been shown in many studies to be superior to shockwave lithotripsy (SWL). The objective was to analyze the stone-free rate after treatment of distal ureteral stones with in situ SWL or URS. MATERIALS AND METHODS: A total of 3,857 SWL treatments were performed at our institution between 1996 and 2001. During this period 45 in situ SWL procedures were performed with the Dornier MFL 5000 lithotripter on distal ureteral stones regardless of the stone size. A total of 262 URS treatments were performed on distal ureteral stones. URS for small (5 mm or less) distal ureteral stones was performed in 110 cases. RESULTS: Distal ureteral stones smaller or equal to 5 mm in size were treated successfully stone free in 78% in one SWL session. Patients required a second SWL in 14% of the cases and 8% of the patients required a third SWL session. URS patients were successfully stone free after the procedure in 97% of the cases. Failed URS that needed an additional URS were performed in 2 and 1% of the patients had one SWL in situ treatment. CONCLUSIONS: URS treatment has shown to be the therapy of choice for distal ureteral stones. It is more effective than SWL treatment in this stone location. In experienced hands URS is a safe though even more invasive procedure than SWL. This can be expected as urologists perform more than 40 URS procedures per year.     

Effect of vibration massage therapy after extracorporeal shockwave lithotripsy in patients with lower caliceal stones

PURPOSE: To determine whether vibration massage influences the results of extracorporeal shockwave lithotripsy (SWL) in patients with lower caliceal stones. PATIENTS AND METHODS: One hundred three patients with lower caliceal stones were entered in the study. Patients were divided into two groups that received either SWL alone (Group A, N = 52) or with vibration massage (Group B, N = 51). There was no statistically significant difference between the two groups in stone size, duration of follow-up, or patient age. The complication, stone-free, and stone recurrence rates of the groups were compared. RESULTS: There was no statistically significant difference between the groups in the number of shockwaves, number of SWL sessions, or shockwave energy. The renal colic rate was higher in Group B than in Group A (P = 0.03). The stone-free rates in Group A and Group B were 60% and 80%, respectively (P = 0.003). The stone recurrence rate was higher in Group A than in Group B (P = 0.0006). CONCLUSIONS: This retrospective study demonstrates that SWL with vibration massage appears to have a beneficial effect on the passage of fragments in patients with lower caliceal stones.     

Endoscopy vs. extracorporeal shockwave lithotripsy in the treatment of distal ureteral stones: ten years' experience.

BACKGROUND: The lower third is the location of the great majority of ureteral stones. Treatment of these stones remains controversial: in situ extracorporeal shockwave lithotripsy (SWL) vs. ureteroscopy (URS). METHODS: During the last decade, 633 distal ureteral calculi were treated at our institution using in situ SWL (Siemens Lithostar electromagnetic lithotripter) in 395 patients and URS (with 11.5F instrument and ultrasonic lithotripsy) in 228 patients. The patients' age and stone size were similar in the two groups. All SWL therapies were performed on an outpatient basis. RESULTS: The overall success rate was 99% for SWL, and the efficiency quotient (EQ) was 92.4%. The treatment was more effective for <10 mm calculi. In the URS group, there was a 92% overall success rate with an EQ at 91.2%. Compared with SWL, URS was more time consuming, at least for the initial cases; often required intravenous sedation; entailed routine placement of a ureteral stent; and more often led to hospitalization. On the other hand, stone clearance was rapid after URS, although most of the SWL patients were stone free at the end of 6 weeks. The cost was similar in the two groups. CONCLUSION: We believe that multiple factors should be considered when deciding the most appropriate approach to distal ureteral calculi. In situ SWL provides optimal first-line treatment for calculi < 10 mm, whereas URS is better reserved for stones >10 mm.     

Lower pole ratio: A new and accurate predictor of lower pole stone clearance after shockwave lithotripsy?

BACKGROUND: Lower pole spatial anatomy is an important determinant of success after extracorporeal shockwave lithotripsy. In the present study, we determine whether there is a significant relationship between lower pole ratio (infundibular length : infundibular width) on preoperative intravenous urograms and stone fragment clearances after shockwave lithotripsy. METHODS: A total of 42 patients with isolated lower pole stones were retrospectively reviewed. Anatomical factors, such as infundibular length, width and infundibulopelvic angle were measured and the lower pole ratio was calculated on pretreatment intravenous urogram. Stone fragment clearance was assessed at three months with a plain abdominal X-ray. RESULTS: The overall three-month stone-free rate was 62%. Mean stone size +/- SD was 10 +/- 4.8 mm, mean infundibular length was 21.7 +/- 6.9 mm, mean infundibular width was 6.1 +/- 2.3 mm, mean infundibulopelvic angle was 62.1 +/- 30.1 degrees and mean lower pole ratio was 4.3 +/- 2.8. Stone-free status after shockwave lithotripsy was significantly related to infundibular length and width as well as to lower pole ratio, but not to infundibulo-pelvic angle. Infundibular length less than 30 mm, width greater than 5 mm and lower pole ratio less than 3.5 were noted to have an improved three-month stone-free rate (P = 0.049, 0.01 and <0.01, respectively). CONCLUSION: Caliceal anatomy is an important consideration for lower pole stone clearance after shockwave lithotripsy. The present study suggests that a lower pole ratio of less than 3.5, which considers both infundibular length and width, is a promising predictor for stone-free status.     

Stone fragility: its therapeutic implications in shock wave lithotripsy of upper urinary tract stones

OBJECTIVE: To analyse the impact of stone composition on stone fragility (fragmentation) and clearance of upper urinary tract stones after shock wave lithotripsy (SWL). MATERIAL AND METHODS: Between 1st July 1998 and 31st July 2001, 300 renal and ureteric units of 290 patients (10 being bilateral) underwent SWL for upper urinary tract calculi. The degree of fragmentation was divided into four types: (I) Excellent, (II) Good, (III) Fair and (IV) No fragmentation. Stone composition was done by X-ray diffraction crystallography. A statistical comparison was made between degree of fragmentation, number of shock waves delivered, voltage setting, number of sessions required and requirements of adjuvant procedures according to the stone composition. RESULTS: Stone analysis revealed that 90% of the patients had calcium oxalate stones. Of these 80% were calcium oxalate monohydrate (COM) and 20% calcium oxalate dehydrate (COD). Struvite, apatite and uric acid stones comprised of 6%, 3% and 1% respectively. Type-I fragmentation was achieved up to 63.96%, 50% and 100% in COD, struvite and uric stones respectively as compared to 44.9% and 44.44% for COM and apatite stones. Type-III fragmentation was seen up to 8.79% and 33.3% respectively in COM and apatite as compared to 5.55% or less in other types of the stones suggesting that COM and apatite stones produce larger fragments. The mean number of shock waves, voltage and number of treatments was significantly higher for COM and apatite stones (p value < 0.005) with a stone free rate of only 65-66% and 65-68% respectively at three months (p value < 0.001). Similarly the number of adjuvant procedures required in COM alone was more, i.e. 31 as compared to 17 procedures in rest of the other kinds of stones (p value < 0.05). CONCLUSION: Stone composition in Indian subcontinent is different from the western world. Fragility of a stone varies with the composition of the stone and affects the therapeutic results.