Electrohydraulic Probe Research Articles

Cracking Difficult Biliary Stones.

Apart from difficult biliary cannulation, biliary stone removal is considered one of the hurdles in endoscopic retrograde cholangiopancreatography. Generally, simple common bile duct (CBD) stones can be removed either with an extraction balloon or a basket. However, there are difficult stones that cannot be removed using these standard methods. The most difficult stones are large CBD stones and impacted stones in a tapering CBD. A few decades ago, mechanical lithotripsy was usually required to manage these stones. At present, endoscopic papillary large balloon dilation (EPLBD) of the biliary orifice has become the gold standard for large CBD stones up to 1.5 cm. EPLBD can reduce the procedural time by shortening the stone removal process. It can also save the cost of the devices, especially multiple baskets, used in mechanical lithotripsy. Unfortunately, very large CBD stones, stones impacted in a tapering CBD, and some intrahepatic duct stones still require lithotripsy. Peroral cholangioscopy provides direct visualization of the stone, which helps the endoscopist perform a probe-based lithotripsy either with an electrohydraulic probe or a laser probe. This technique can facilitate the management of difficult CBD stones with a high success rate and save procedural time without significant technical complications.

Editorial comment

There has been relatively little controversy in the management of upper ureteral stones over the years, mainly because access to the upper ureter with available ureteroscopes was always a chancy affair. Additionally, if the stone could be accessed, fragmentation was limited for practical purposes to the electrohydraulic probe or possibly the Coumarin dye laser. In the past few years, however, small, flexible, steerable ureteroscopes have become widely available, with a parallel evolution in the technique of URS, particularly with the use of the access sheath. Thus, it is now routinely possible to access the upper ureter in the vast majority of patients. Efficiency and cost of treating proximal ureteral stones: Shock wave lithotripsy versus ureteroscopy plus holmium:yttrium-aluminum-garnet laserUrologyVol. 64Issue 6PreviewTo compare the success rates, cost effectiveness, and efficiency of ureteroscopy (URS) and extracorporeal shock wave lithotripsy (ESWL) for proximal ureteral stones. Full-Text PDF

Identifying stone composition using infrared analysis of filtered urine after ureteroscopic lithotripsy.

With the development of small-caliber ureteroscopes and lithotripsy devices, it is now possible to perform intracorporeal stone fragmentation without dilatation of the ureteral orifice. Ureteral stones are typically fragmented into small particles that can be difficult to retrieve for stone analysis. Infrared spectroscopy (IRS) of the precipitate from urine after intracorporeal lithotripsy represents a method for obtaining stone analysis. A total of 69 patients underwent ureteroscopic lithotripsy with the holmium laser or the electrohydraulic probe for stones in the ureter (N = 65) or kidney (N = 4). Each patient's bladder was then drained and the urine filtered. The resulting precipitate was analyzed using IRS. The amount of material for analysis was < or =1 mg in 56 patients (82%). Stone composition was positively identified in 44 patients (64%). Material suitable for analysis was recovered from 73% of patients when the bladder was drained with a cystoscope sheath compared with 43% when a urethral catheter was used (P = 0.03). There was no significant difference in pretreatment stone size in the patients who had a positive v a negative result (11.7 mm v 10.9 mm; P = 0.06). Similarly, the stone location was not significantly related to the likelihood of positive analysis (P = 0.29). Straining the urine after ureteroscopic intracorporeal lithotripsy and analyzing the precipitate with IRS is able to identify stone composition in the majority of patients. This method is especially useful in the setting of holmium laser lithotripsy, in which the majority of the stone is converted to spontaneously passable particles.

Treatment of urinary tract stones.

Replacement of open surgery with minimally invasive techniques for treating stones in the renal tract has greatly reduced patients' morbidity and mortality and the period of hospitalisation and convalescence. Extracorporeal shockwave lithotripsy does not require anaesthesia and requires little analgesia so that treatment can be given on an outpatient basis, and there is no wound to heal. Only a small puncture site is needed for percutaneous endoscopic lithotomy, and with the advent of prophylactic antibiotics there are few complications. Of renal stones, about 85% can now be successfully treated by extracorporeal lithotripsy alone, and almost all of the stones too large or hard for lithotripsy can be treated endoscopically, with ultrasonic or electrohydraulic probes being used to fragment the stone. Stones in the upper and lower thirds of the ureter can be treated by extracorporeal lithotripsy, but stones in the middle third, which cannot normally be visualised to allow focusing of the shockwaves, usually require ureteroscopy. Nearly all bladder stones can be treated by transurethral endoscopy with an electrohydraulic probe. Only the largest renal tract stones still require open surgery.

The Electromechanical Impactor: The Results of Design Modifications

The first generation clinical electromechanical impactor was a 5F device that used a 3.0F electrohydraulic probe within a coiled spring with a blunt solder end cap. Clinical trials showed that this device fragmented 70% of the calculi but failed to fragment the harder stones. Applying the principle that impact kinetic energy is most dependent on velocity (KE = 1/2 MV2), 3 major design modifications were made to improve fragmentation efficiency: 1) the spring was changed from an extension to a compression type that captured and used more of each electrical spark, 2) the tip was changed from solder to lightweight titanium and 3) the tip shape was changed from blunt to conical. The result was a 41% increase in impact kinetic energy, a 40% increase in probe longevity and successful in vitro fragmentation of the harder calculi without compromise in tissue safety as determined by membrane perforation studies.

Direct Percutaneous Pouch Cystostomy with Endoscopic Lithotripsy for Calculus in a Continent Urinary Reservoir

Continent urinary reservoirs are an accepted mode of urinary diversion in appropriate patients. Such procedures are associated with long-term complications. A patient who underwent a continent urinary diversion (modified Indiana pouch) 4 years ago for a neurogenic bladder presented with a large irregular calculus in the pouch. Endoscopic attempts to remove the calculus through the stoma were unsuccessful and extracorporeal shock wave lithotripsy failed to fragment the pouch calculus. Finally, an endoscopic approach through a direct percutaneous pouch cystostomy, and use of ultrasonic and electrohydraulic probes resulted in successful fragmentation and removal of the calculus.

New tip design and shock wave pattern of electrohydraulic probes for endoureteral lithotripsy.

A new tip design of a 3.3F electrohydraulic probe for endoureteral lithotripsy was evaluated in comparison to a regular probe. The peak pressure, as well as the slope of the shock front, depend solely on the voltage. Increasing the capacity leads merely to broader pulses. A laser-like short high-pressure pulse has a greater impact on stone disintegration than a corresponding broader low-pressure pulse of the same energy. Using the regular probe, only positive pressures were obtained. Pressure distribution around the regular tip was approximately spherical, whereas the modified probe tip "beamed" the shock wave to a great extent. In addition, a negative-pressure half-cycle was added to the initial positive peak pressure, which resulted in a higher maximal pressure amplitude. The directed shock wave had a greater depth of penetration into a model stone. Thus, the ability of the new probe to destroy harder stones especially should be greater. The trauma to the ureter was reduced when touching the wall tangentially. No difference in the effect of the two probes was seen when placing the probe directly on the mucosa.

Non-surgical management of bile duct stones refractory to routine endoscopic measures

Endoscopic sphincterotomy and percutaneous approaches to the biliary tract have revolutionized the treatment of bile duct stones. Both the endoscopic and transhepatic approaches are less invasive than open surgery. This is an advantage for the mostly elderly and frail patients with common bile duct stones. Other patients with intrahepatic stones, e.g. young patients with oriental lithiasis, may also profit from the non-surgical approach. In this latter group it is often difficult for the surgeon to obtain access to the stone-bearing bile ducts. Due to the anatomical situation, size or impaction of stones the non-surgical approach, including mechanical disintegration, may primarily fail. Several techniques such as intracorporeal lithotripsy using electrohydraulic probes or laser light, extracorporeal shockwave lithotripsy or direct contact dissolution are now available and often allow complete clearance of the bile ducts. If a kidney lithotripter with radiographic devices is available, it should be used after an attempt at mechanical lithotripsy has failed (Figure 1). According to the literature, experience with this method is greater than with any other ‘third-step approach’. The procedure is simple, relatively safe and successful in approximately 80% of patients. However, in at least one third of patients, several sessions have to be performed and further endoscopy is frequently required for extraction of fragments. Intracorporeal techniques may become the procedure of choice in the future, at least in patients with common bile duct stones. At the moment, however, the different devices are still not fully developed and too susceptible to damage. A further major drawback, especially with high-energy electrohydraulic intracorporeal lithotripsy, is the danger of bile duct injury or even perforation, so that most procedures must be performed under optical control. The use of contact dissolution cannot generally be recommended. Treatment with mono-octanoin or modified mono-octanoin solvents takes too long, is often not successful and has a high rate of side-effects. MTBE may shorten the procedure considerably, but is suitable only for cholesterol stones, and the danger of spill-over into the intestine with absorption and systemic side-effects has to be weighed against the probability of success.

Endoscopic Management of Difficult Bile Duct Stones

More than 90% of all common bile duct concrements can be removed via the endoscopic retrograde route via endoscopic sphincterotomy, stone extraction by baskets and balloon catheters, or mechanical lithotripsy. Oversized, very hard or impacted stones, however, often still resist conventional endoscopic therapy. Promising new or improved approaches for the treatment of these stones are intracorporeal or extracorporeal shock wave lithotripsy. Shockwave lithotriptors for extracorporeal shockwave lithotripsy are currently available worldwide. However, for the waterbath first generation devices, general anesthesia is required since shockwaves are very painful. Furthermore, an x-ray localization system is essential to visualize the stones after having filled the bile duct over a nasobiliary catheter. An average of two shockwave treatments with additional two to four endoscopic sessions are required. ln tracorporeal lithotripsy promises more comfort and less effort for the patient. Shockwaves are generated either by means of the spark gap principle (electrohydraulic probes) or by laser-induced plasma generation. Laser-induced shockwave lithotripsy appears to be more safer, since with dye and solid state lasers, athermal, well-controlled shockwaves can be generateJ without the risks for duct perfo ration (as described for the electrohydraulic system). Furthermore, a recently developed stone-tissue detection system integrated in a new dye laser system enchances the safety of laser-induced lithotripsy. ln consequence, lithotripsy without direct endoscopic control appears possible in selected cases.

Pressure Threshold for Shock Wave Induced Renal Hemorrhage

Studies were performed with an interest in determining a pressure threshold for extracorporeal shock wave induced renal damage. Histological evidence of intraparenchymal hemorrhage was used as an indicator of tissue trauma. Depilated C3H mice were anesthetized and placed on a special frame to enhance visualization and treatment of the kidneys in situ. A Wolf electrohydraulic generator and 9 French probe designed for endoscopic use were utilized to expose the kidneys to 10 double spherically divergent shock waves. Measurements of the shock waves revealed two positive pressure peaks of similar magnitude for each spark discharge. The kidneys were exposed to different peak pressures by choice of distance from the spark source and were removed immediately after treatment for histologic processing. A dose response was noted with severe corticomedullary damage apparent following 15 to 20 MPa shocks. Hemorrhage was more apparent in the medulla where evidence of damage could be seen following pressures as low as three to five MPa. When a latex membrane was interposed to prevent possible collapse of the initial bubble from the spark source against the skin surface, histological evaluation revealed substantial reduction of severe tissue damage associated with the highest pressures tested, 20 MPa. However, the threshold level for evidence of hemorrhage remained about three to five MPa. Hydrophonic measurements indicated that the membrane allowed transmission of the acoustic shock waves and suggested that collapse of the bubble generated by electrohydraulic probes may have local effects due to a cavitation-like mechanism.

Experience with Management of Stones Formed Within Kock Pouch Continent Urinary Diversions

The treatment of stones within Kock pouch urinary diversions is challenging yet gratifying in terms of reduction of symptoms. Using endoscopic means, the procedures can be done totally on an outpatient basis, with a considerable reduction in cost. Extracorporeal shock wave lithotripsy has limited, if any, place in the treatment of this particular urologic problem. If a full endourologic armamentarium is not available, the procedure can be accomplished with an operating nephroscope, direct grasping instruments, and an electrohydraulic probe, although the procedure may take longer. Technical modifications in the construction of the Kock pouch, and possibly routine postoperative endoscopy to remove any exposed staples, and considerably reduce the incidence of this complication.

Electrohydraulic Lithotripsy in the Ureter

Intravesical lithotripsy using electrohydraulic probe appears to be a rapid and safe technique to treat ureteral stones that are too large for intact extraction and inaccessible to ESWL. Strict adherence to the guidelines that have been discussed must be maintained to assure its safety.

The Pulsed Dye Laser for Fragmenting Urinary Calculi

The properties of a laser which effect stone fragmentation have been studied. The pulsed dye laser emitting at 504nm. in one microsecond duration pulses appears to be the optimum out of a wide range of parameters tested. The laser is coupled to a 200 micron core fiber; this complete with its cladding has a total diameter of only 0.25mm. Most calculi are fragmented by a series of pulses of up to 30mJ. The system is used by firing bursts of pulses with the fiber actually in contact with the stone. The result is a very controlled fragmentation which is particularly suited to use in the confines of the ureter. This modality of treatment utilises less energy than ultrasound or electrohydraulic probes to fragment a stone and the very fine, flexible fiber represents a considerable miniaturisation.

Percutaneous Nephrolithgtripsy: A Functional and Morphological Study

Percutaneous removal of renal calculi requires a nephrostomy track, irrigation and lithotripsy The purpose of this study is to investigate the effects of these procedures on renal function and anatomy.Renal access was obtained through a small left subcostal incision and a 22 Ch nephrostomy track was formed by fine parenchymal puncture and serial dilation in 15 dogs. Three liters of glycine solution were perfused through these tracks. In a further 16 dogs, human calculi were placed transparenchymally in the renal pelvis and disintegrated under vision through the Wolf nephroscope using an ultrasonic probe in8and electrohydraulic probe in 8. Assessments were made in all animals at 48 hours or 6 weeks by creatinine clearance, microfil casts, contrast radiography and ex-situ conventional and digital subtraction angiography.There was no significant urinary leakage or bleeding from the nephrostomy track at 48 hours. There was a small track hematoma and at 6 weeks a surface dimple and fine linear parenchymal scar. There was no ureteric or pelvic damage. Microfil casts showed small track defects at 48 hours resolving to a fine scar at 6 weeks. All angiograms were normal. Some IVtPs displayed minor track defects at 48 hours but all were normal at 6 weeks. Corrosion casts and subtraction angiography demonstrated no significant vascular defects. Creatinine clearance showed no significant difference between experimental and control sides. Occasionally, intra pelvic scatter of fine calculus fragments was seen at 48 hours but none was detectable at 6 weeks.Transparenchymal nephrostomy, irrigation and nephrolithotripsy caused initial minor anatomical defects that rapidly resolved and were not associated with any loss of renal function.