Fragmentation Of Calculi Research Articles

Enlargement of calcium oxalate stones to clinically significant size in an in-vitro stone generator.

To develop and validate an in vitro method suitable for the quantitative investigation of the growth of calcium oxalate stones through to a clinically significant size. Small fragments of calcium oxalate calculi were suspended in a mixed suspension/mixed product removal crystalliser supplied with artificial urine supersaturated with calcium oxalate. The fragments were weighed at regular intervals until they reached approximately equal 500 mg. The results were plotted as weight against time and fitted to equations corresponding to constant increase in diameter, surface area-controlled and constant-deposition growth patterns. The choice of the most appropriate model was based on the squared regression coefficient (r2). Eight fragments (2-6 mm in diameter) were grown to approximately 10 mm in diameter over periods from 137 to 369 h. Seven of the growth curves were best-fitted (r2 > or = 0.988) by the equation w = kt(3/2) + c, where w is the weight, k is a growth constant, t is the time and c is a constant approximating to the initial weight. This corresponds to a surface area-dependent mechanism. The growth of these small fragments to a clinically significant size accelerated throughout the experimental period in a way which was consistent with a surface area-dependent mechanism. We have developed a resilient model suitable for studying the kinetics of calcium oxalate stone growth in vitro.

Clinical outcomes in patients who undergo extracorporeal shock wave lithotripsy for chronic calcific pancreatitis

Background: There is controversy as to whether extracorporeal shock wave lithotripsy fragmentation and ERCP retrieval of pancreatic stones are associated with relief of chronic pain or relapsing attacks of pancreatitis. Our most recent experience with this technology is reviewed. Methods: Forty patients with chronic calcific pancreatitis who required extracorporeal shock wave lithotripsy between 1995 and 2000 to facilitate pancreatic duct stone removal were retrospectively reviewed. Data collected included patient presentation, number of lithotripsy and ERCP sessions required, complications, and outcomes measures to include pre- and post-ESWL pain scale, monthly oxycodone (5 mg)-equivalent pills ingested, yearly hospitalizations, and need for subsequent surgery. Results: A single extracorporeal shock wave lithotripsy session was required for 35 patients who underwent a total of 86 ERCPs to achieve complete stone extraction from the main pancreatic duct. Minor complications occurred in 20%. There was one episode of pancreatic sepsis that was treated with antibiotics and removal of an occluded pancreatic prosthesis. At a mean [SD] follow-up of 2.4 (0.6) years, 80% of patients had avoided surgery and there was a statistically significant decrease in pain scores (6.9 [1.3] vs. 2.9 [1.1]; p = 0.001), yearly hospitalizations for pancreatitis (3.9 [1.9] vs. 0.9 [0.9]; p = 0.001), and oxycodone-equivalent narcotic medication ingested monthly (125 [83] vs. 81 [80]; p = 0.03). Conclusions: Extracorporeal shock wave lithotripsy fragmentation of pancreatic duct calculi in conjunction with endoscopic clearance of the main pancreatic duct is associated with significant improvement in clinical outcomes in most patients with chronic pancreatitis. (Gastrointest Endosc 2002;56:496-500.)

Erbium: YAG laser Lithotripsy Mechanism

We tested the hypothesis that the mechanism of long pulse erbium:YAG laser lithotripsy is photothermal. Human urinary calculi were placed in deionized water and irradiated with erbium:YAG laser energy delivered through a sapphire optical fiber. Erbium:YAG bubble dynamics were visualized with Schlieren flash photography and correlated to acoustic emissions measured by a polyvinylidene fluoride needle hydrophone. The sapphire fiber was placed either parallel or perpendicular to the calculus surface to assess the contribution of acoustic transients to fragmentation. Stones were irradiated using desiccated stone irradiated in air, hydrated stone irradiated in air and hydrated stone irradiated in water. Ablation crater sizes were compared. Uric acid stones were irradiated in water and the water was assayed for cyanide. During the early phase of vapor bubble expansion, acoustic transients had minimal effects on calculus fragmentation. Fragmentation occurred due to direct absorption of laser energy transmitted to the calculus through the vapor channel between the sapphire fiber tip and calculus. The forward axial expansion of the bubble occurred more rapidly than the radial expansion. A parallel oriented fiber on the calculus surface produced no fragmentation but generated larger amplitude acoustic transients compared to perpendicular orientation. In perpendicular orientation the erbium:YAG laser did not generate any collapse acoustic waves but fragmentation occurred. Crater width was greatest for desiccated stones irradiated in air (p <0.03). Cyanide production increased as erbium:YAG irradiation of uric acid calculi increased, (r2 = 0.98). The erbium:YAG laser fragments stones through a photothermal mechanism.

Bare naked baskets: optimizing ureteroscopic stone extraction

Baskets placed through the working channels of flexible ureteroscopes limit mobility and irrigant flow. We describe a new technique to minimize these limitations. An unsheathed “bare naked” basket affords enhanced ureteroscopic efficacy by limiting obstruction of the working channel. We have used the technique clinically to treat stones in difficult locations successfully and to remove fragments of calculi after ureteroscopic lithotripsy.

DOSE A URETERAL ACCESS SHEATH FACILITATE URETEROSCOPY?

Ureteral access sheaths were initially developed to facilitate difficult ureteroscopic access. However, to our knowledge no formal evaluations have been performed to assess the routine use of ureteral access sheaths. Therefore, we prospectively analyzed intraoperative time, symptomatic outcome, major complications, stone-free rate and overall costs related to the routine use of a new ureteral access sheath during standard ureteroscopic procedures. Patients undergoing 6.5Fr semirigid or 7.5Fr flexible ureteroscopy were prospectively randomized to unaided ureteroscopy with no access sheath or ureteroscopy via a 12-14Fr ureteral access sheath. Patients who required ureteral dilatation were randomized to the ureteral access sheath used as a dilator or a standard 18Fr ureteral balloon dilator. Patients were evaluated postoperatively on days 0, 1 and 6 with a questionnaire to assess pain, irritative symptoms and complications. The stone-free rate and long-term complications were determined by excretory urography or computerized tomography at 3 months. Enrolled in the study were 59 consecutive patients, who underwent a total of 62 ureteroscopic procedures. Of the 47 patients (76%) who did not require ureteral dilatation 23 (49%) underwent ureteroscopy via the ureteral access sheath and 24 (51%) underwent unaided ureteroscopy. Seven of the 15 patients (28%) who required ureteral dilatation underwent access sheath dilatation, while balloon dilatation was performed in 8. There was no significant difference in postoperative symptoms, complication rate or stone-free status in the access sheath and nonaccess sheath groups in patients not requiring ureteral dilatation (p <0.05). A significant increase in postoperative symptoms was noted when the balloon was used as a dilator compared to the access sheath. Operative time and costs in all patients who underwent access sheath dilatation were less than in those in whom the access sheath was not used. In the 15 patients who required dilatation 71% of access sheath and 100% of balloon dilatations were successful. Routine use of a ureteral access sheath appears to facilitate semirigid and flexible ureteroscopy by decreasing operative time and costs, allowing direct visualization of ureteroscope insertion with simple ureteral re-entry and assisting renal and ureteral access with minimal associated morbidity. A ureteral access sheath should be considered for routine ureteroscopic procedures.

INFUNDIBULOPELVIC ANATOMY AND CLEARANCE OF INFERIOR CALICEAL CALCULI WITH SHOCK WAVE LITHOTRIPSY

We evaluate the significance of inferior caliceal radiographic anatomy and determine its influence on successful fragmentation and clearance of inferior caliceal calculi with extracorporeal shock wave lithotripsy (ESWL). Between November 1996 and February 1998, 88 patients and 90 renal units with single or multiple inferior caliceal calculi of all sizes and composition were treated with ESWL. The size, number and area of calculi, length and width of the stone bearing inferior calix and infundibulopelvic angle were determined on pretreatment excretory urography. The infundibulopelvic angle was measured by 2 methods using the angle between the inferior caliceal infundibular and ureteral axes (angle 1), and between the infundibular and ureteropelvic axes (angle 2). Cases with residual fragments not clearing within 6 months of satisfactory fragmentation after lithotripsy were considered failures. Overall stone clearance at 6 months was achieved in about 72% of the renal units. Infundibular length was 30 mm. or less in 77% of successful cases and in 64% of failures. Similarly, the smallest infundibular width of 5 mm. or more was found in 75% of successful cases compared to 41% of failures. Angle 1 of 35 degrees or more was observed in 73% of cases with compared to 18% without clearance. Angle 2 of 45 degrees or more was seen in 71% of successful cases compared to 9% of failures. The chances of a patient becoming stone-free with all favorable criteria of infundibular length 30 mm. or less, infundibular width 5 mm. or greater and infundibular ureteropelvic angle 45 degrees or greater was 100% (23 patients). Radiographic features of a stone bearing inferior calix and its relation to the renal pelvis can be easily measured on standard excretory urography. An infundibular width of 5 mm. or more and infundibulopelvic angle 1 of 35 degrees or more or angle 2 of 45 degrees or more were statistically significant factors of radiographic anatomy in stone clearance following ESWL. Inferior caliceal length was not statistically significant, although length of 30 mm. or less appeared to be more favorable for stone clearance. The ideal treatment of inferior caliceal calculi in patients with all 3 favorable criteria is ESWL.

Host, heredity and helicobacter

<h3>Introduction</h3> Extracorporeal shock wave lithotripsy (ESWL) of pancreatic duct stones, followed by endoscopic retrograde cholangio-pancreaticography (ERCP) with mechanical clearance of the pancreatic duct, and subsequent stenting is an established treatment...

Endoscopic intracorporeal lithotripsy for sialolithiasis

Purpose: This article describes a technique of salivary gland endoscopy using a 2.1-mm endoscope with a 1-mm working channel. The technique allows intracorporeal lithotripsy under endoscopic control. Two types of energy to produce calculi fragmentation were analyzed. Patients and Methods: Of 39 patients who presented with obstructive sialoadenitis, endoscopic treatment was possible in 27. Eighteen had a diagnosis of Sialolithiasis. Intracorporeal lithotripsy was done under endoscopic control in these patients. Laser energy was used to produce fragmentation in 3 cases and pneumobalistic energy in 9. In 6 cases, the calculi were extracted with forceps. Results: Fifteen patients are free of stones and symptoms after a 6-month follow-up. Fragmentation and extraction of the calculi were not possible in 3 patients. Two of these patients required open surgery. The other patient is under observation. Conclusions: The use of endoscopes with a working channel allows irrigation to improve visibility during exploration. Both extraction of calculi and lithiasis fragmentation using different energies can be carried out through the channel. In this series, pneumoballistic energy (Lithoclast) has been shown to produce calculus fragmentation with more efficiency than lasertripsy (Dornier Impact). When dilation and placement of a canula (Abocath 16 G) was done 2 days preoperatively, endoscopy was performed more easily. Postoperative drainage has proven effective in avoiding complications.

Mechanical impactor employing Nitinol probes to fragment human calculi: fragmentation efficiency with flexible endoscope deflection.

The Browne Pneumatic Impactor (BPI; Browne Medical Systems, Minneapolis, MN) is a new mechanical lithotripter that relies on a pneumatically driven metal probe. It can be employed through both rigid and actively deflectable flexible endoscopes. Prior in vivo studies have shown excellent fragmentation of hard human calculi while employing the BPI with active endoscope deflection of as much as 45 degrees. In this study, we set out to define the efficiency of stone fragmentation with active endoscope deflection and to quantify the extent of retrograde stone migration that is often noted when mechanical lithotripters are employed. Pressure transducer testing of the BPI revealed an inverse relation between increased deflection of the endoscope and transduced voltage. Calculus fragmentation tests showed that as the endoscope was actively deflected to 90 degrees, the BPI still was able to fragment human calcium oxalate monohydrate calculi into extractable fragments with as few as six pulses. The maximum active endoscope deflection was 95 degrees with the 0.020-inch Nitinol probe passed through the working channel. At this deflection, the BPI was able to fragment an 8 mm pure calcium oxalate monohydrate calculus into two fragments after 14 pulses. Retrograde migration was evaluated by employing the BPI in a simulated ureter in a waterbath. The travel distance of a 5-mm 5-g calculus with one pulse averaged 12.2 mm (range 1-44 mm). Smaller, less dense calculi travelled farther. A rebound effect was occasionally noted, and this was associated with an off-center delivery. In conclusion, the BPI is an efficient mechanical lithotrite able to fragment hard human calculi when employed with active endoscope deflection of as much as 95 degrees. Delivered energy decreased with active endoscope deflection, but this change did not prevent fragmentation. Retrograde migration was an important variable more notable with smaller calculi.

Outpatient fragmentation of ureteral calculi with mini-ureteroscopes and laser lithotripsy.

Laser lithotripsy with mini-ureteroscopes is a minimally invasive method to fragment ureteral calculi. This study reviewed the efficacy and morbidity of outpatient laser lithotripsy for the treatment of ureteral calculi. The 248 patients were initially treated by outpatient ureteroscopy and laser lithotripsy with the Candela pulsed-dye laser over a period of 3 1/2 years. Thirty-six patients had prior unsuccessful fragmentation of ureteral calculi by SWL. Twenty-eight patients had undergone unsuccessful ureteroscopy with attempted basket extraction or attempted fragmentation with methods other than laser. Calculi were located in the upper ureter in 31% and in lower ureter in 69% of these patients. The 1-month stone-free rate was 92% for upper ureteral calculi and 96% for lower ureteral calculi, with an overall success rate of 94.7%. Ninety per cent of the patients were discharged the same day and 96% within 23 hours. Hospital admission was needed in only 4% of patients. Parenteral analgesia was required in 18% of patients, and major complications occurred in 0.8%. The combination of mini-ureteroscopes and laser lithotripsy is an effective method for fragmentation of ureteral calculi in outpatients with low morbidity and few complications.

Actively deflectable, flexible cystoscopes: no longer solely a diagnostic instrument.

The recent evolution of actively deflectable, flexible endoscopes has included the flexible cystoscope. Improvements in optics, deflectability, and the size of the outer sheath and working channel have been accomplished. A superior flexible cystoscope is one with an outer sheath of 16F or less and working channel large enough to admit standard endoscopic instruments (> or = 6F). The 180 degrees two-way thumb-directed deflection and a removable light bundle are significant improvement. We present 55 patients with either urethral, bladder, or upper urinary tract lesions who were treated at the bedside using the flexible cystoscope in many settings. Local anesthesia alone was usually used. Flexible cystoscopy was also used for emergency intraoperative consultation requiring endoscopy. A treatment cart was constructed consisting of a light source, endoscopic instruments, irrigating supplies, and the endoscope. Urethral strictures, perforation, and bladder neck contractures were treated. Ureteral catheters were placed under direct vision. Removal of ureteral stents and foreign bodies, treatment of small bladder tumors with the Nd:YAG laser, and fragmentation of bladder calculi with the pulsed-dye laser were also therapeutic applications. Explanations of each treatment type and the instruments used concurrently with this endoscope are provided.

Nonvisual Laser Lithotripsy Aided by Plasma Spectral Analysis: Viability Study and Clinical Application

Nonvisual laser lithotripsy implies laser fragmentation without the aid of endoscopic or direct vision. Using the laser delivery fiber for retrograde transmission of plasma spectrum and its analysis on an optical multichannel analyzer, we designed a project with the objective of identification and fragmentation of calculi by continuous analysis of the plasma feedback spectrum. We were successful in achieving the objectives in the in vitro and ex vivo studies. In the in vivo studies we successfully recorded the plasma spectrum of the stones from inside the ureter and monitored the process of fragmentation with the laser. We have been able to identify the problems for its clinical application. We conclude that by monitoring the feedback spectrum of plasma emission, nonvisual laser lithotripsy is reliable and safe, and can be used successfully in patients with some modifications. Its development is not to replace established endoscopic lithotripsy procedures but rather as an additional armament for the urologist in special situations. Also, the technique can be further exploited for a variety of clinical uses.

Fragmentation of Biliary Calculi in 71 Patients by Use of Intracorporeal Electrohydraulic Lithotripsy

Failure of percutaneous or endoscopic removal of biliary calculi is often associated with impacted stones or stones larger than 1.5 cm. In these difficult cases, intracorporeal electrohydraulic lithotripsy (EHL) is a method that allows large stones to be fragmented and removed percutaneously or endoscopically. In this study, the authors expand their experience with EHL and further evaluate the safety and efficacy of this technique to remove biliary tract calculi. Intracorporeal electrohydraulic lithotripsy was used to treat 71 patients with calculi in the bile ducts (n = 35) or gallbladder (n = 36). Access was obtained by means of a surgical T-tube tract (n = 16), percutaneous transhepatic biliary drainage (n = 14), percutaneous cholecystostomy (n = 36), an intraoperative approach during common duct exploration (n = 2), and at endoscopic retrograde cholangiopancreatography (n = 3). EHL lithotripsy was effective in fragmenting all biliary stones in 69 of the 71 patients (97%). All of the stone fragments were removed in 67 of these 69 patients (94%). Major complications, including bile peritonitis and gallbladder necrosis, occurred in five patients; however, all major complications were related to the initial percutaneous drainage or tract dilation. No significant complications were directly attributable to the EHL procedure. Intracorporeal EHL is a safe and effective method that can be used to improve the success of percutaneous and endoscopic biliary calculi removal.

Mechanisms Responsible for Diminished Fragmentation of Ureteral Calculi: An Experimental and Clinical Study

We molded 24 synthetic stones (mean weight 680mg., range 641 to 715) from a commercial mixture of gypsum, silica, cellulose and polyvinyl acetate. Each stone was subjected to 400 shocks on a Wolf 2300 Piezolith and groups of 6 stones were treated in 4 different modes. Mean amounts fragmented were 243 ± 18mg. in a free environment, 62 ± 18mg. confined loosely in a latex tube, 22 ± 8mg. impacted in the tube and 30 ± 8mg. impacted alongside a 7F stent.During a 30-month period 118 patients received in situ extracorporeal shock wave lithotripsy for ureteral calculi using the same lithotriptor. The mean stone burden was 11.4mm. (range 4 to 29). Success was greater for patients with calculi 10mm. or less than for those with stones greater than 10mm. (71% versus 51%, p <0.05), despite the former group receiving less shocks (5,404 versus 7,491). The influence of size was then excluded by studying the number of shocks delivered per mm. of calculus. Patients receiving 500 to 699 shocks per mm. showed a higher success rate than those receiving a smaller number of shocks per mm. Treatment with a greater number of shocks per mm. did not improve success rate.The experimental study demonstrated that confinement and impaction significantly diminish the rate of fragmentation of calculi. However, the clinical study suggested that there may be an optimum number of shocks per mm. that should be delivered. Treatment beyond this point fails to improve results. The 28% failure rate even in those receiving the highest number of shocks per mm. suggests that large, impacted calculi are unsuitable for treatment with in situ shock wave lithotripsy on this machine.

The feasibility of blind fragmentation in laser lithotripsy

In laser lithotripsy, it has been found that calculi fragmentation is always accompanied with the formation of a plasma which has two characteristics, i.e. the acoustic signal or shock waves, and the optical signal or plasma emission. By monitoring the feedback signals of the shock waves, the temporal behaviour and the spectra of plasma emission, the feasibility of so-called blind fragmentation has been investigated. The shock wave feedback is found to be not as reliable as the plasma emission feedback and the use of an optical multichannel analyser system to detect, analyse and display the spectra of the feedback plasma emission has proved to be reliable and direct for blind fragmentation. The blind fragmentation technique has been found to be successful in ex vivo experiments in which stones were inserted into pigs' ureters and then fragmented without the use of a ureteroscope. It has also been investigated in vivo in studies from about one dozen patients, and for the first time a series of the plasma spectra have been obtained and analysed in vivo. These indicate promising prospects for the clinical application of the technique and, in addition, application to real-time stone composition analysis. The technique has also been tested for biliary stone fragmentation and for laser angioplasty, again the results have shown good prospects.

Basic mechanisms in laser lithotripsy: 2 Spectroscopic analysis

The basic mechanisms in laser lithotripsy have been studied experimentally and theoretically. A model, in which the stone surface is first vaporized, ablated and then ionized by absorption of the remaining laser pulse energy to form a plasma, and finally fragmented by the expansion of the resulting plasma in a shockwave, is presented and discussed to explain the mechanisms of stone fragmentation. The spectral analysis of the plasma produced by different calculi shows the important role of calcium atoms in plasma formation. The plasma temperature and electron density for calcium abundant calculi are calculated to be 104K and 1018 cm−3, respectively. The role of multiphoton ionization and cascade ionization in the plasma formation consisting chiefly of calcium (Ca) atoms are evaluated respectively. The conclusion drawn is that these two ionization mechanisms lead to strong ionization of calcium atoms and sharp absorption of laser energy which, in co-operation with the inverse Bremsstrahlung effect, leads to plasma formation, expansion and finally calculi fragmentation.

Basic mechanisms in laser lithotripsy. 1: Optoacoustic-mechanical analysis

Extensive studies on laser lithotripsy of urinary and gall calculi using a microsecond pulsed dye laser have yielded information on the mechanism of plasma initiation, expansion and shock wave fragmentation relevant to the determination of optimum fragmentation conditions. The key to plasma formation lies in the initial absorption of laser energy by the calculus surface to produce a sufficient density of localized vapour to absorb strongly laser energy. The subsequent ionization of the vapour by the further absorption of laser energy leads to plasma formation. The absorbance of several calculi pigmentations have been measured giving an indication of the individual susceptibility to laser induced breakdown. The plasma threshold is measured to be fluence dependence, which is caused by the vaporization and the further heating of the vapour. The transient expansion of the plasma imparts an impulse on stone and induces a sharp shock wave with peak pressure as high as 10 kilobar leading to the fragmentation of calculi.

Extrusion of calculi from upper urinarytract into perinephric and periureteric tissues during endourologic stone surgery

We report on 11 patients in whom fragments of calculi were extruded into the perinephric or periureteric tissues at the time of endourologic stone surgery. All patients have been managed conservatively. In 2 patients ureteric strictures developed, but these were probably secondary to an electrical injury as a result of electrohydraulic lithopaxy. The remaining 9 patients have not experienced serious sequelae as a result of the calculus extrusion.

Comparison of Alfentanil and Ketamine Infusions in Combination with Midazolam for Outpatient Lithotripsy

Sixty unpremedicated outpatients undergoing elective extracorporeal shock wave lithotripsy using an unmodified Dornier HM-3 lithotriptor were randomly assigned to receive an intravenous infusion of either alfentanil or ketamine as an adjuvant to midazolam for sedation and analgesia. Although both drug regimens allowed the maximal number of shock waves and energy level, the alfentanil group had significantly better calculi fragmentation (78% vs. 50% of patients with fragments less than 2 mm). Ketamine infusion provided superior intraoperative cardiorespiratory stability; however, it was associated with more disruptive movements (22 vs. 5) and dreaming (35% vs. 5%) during the procedure (P less than 0.05). Postoperatively, confusion also occurred more frequently in the ketamine-treated patients (31% vs. 5%, P less than 0.05). Alfentanil infusion was associated with more episodes of hemoglobin oxygen desaturation to less than 90% (12 vs. 2, P less than 0.05), itching (23% vs. 4%, P less than 0.05), and ability to recall intraoperative events (45% vs. 12%, P less than 0.05). The incidence of postoperative nausea was decreased (not significantly) in the alfentanil group (32% vs. 54%). The mean anesthesia time was similar in both groups; however, discharge times (means +/- standard deviations) were shorter in the alfentanil group (142 +/- 42 min vs. 161 +/- 31 min, P = 0.05). These data suggest that although both techniques proved effective for anesthesia in outpatients undergoing immersion lithotripsy, alfentanil is superior to ketamine as part of a sedative-analgesic technique because of the improved recovery profile and calculi fragmentation.

Percutaneous Biliary Stone Extraction: Radiologic and Combined Radiologic-Endoscopic Techniques

In certain clinical settings, percutaneous fragmentation and extraction is an acceptable option for the treatment of biliary calculi. There are three potential percutaneous access routes: a mature surgical T-tube tract, a percutaneous transhepatic entry into a bile duct, or a percutaneous entry into the gallbladder. Fluoroscopic guidance is used to locate and extract the calculi. Fragmentation of large calculi can be accomplished using mechanical, laser, electrohydraulic, or ultrasonic lithotripsy. Direct dissolution therapy is also being investigated to decrease stone load. A multidisciplinary approach using a combination of endoscopic and radiologic techniques can be helpful.