Intracorporeal Lithotripsy

Updated: Dec 11, 2018
Author: Michael Grasso, III, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS 

Overview

Background

Endoscopic lithotripsy refers to the visualization of a calculus in the urinary tract and the simultaneous application of energy to fragment the stone or stones into either extractable or passable pieces.

Many calculi in the upper urinary tract are treated with extracorporeal shockwave lithotripsy (ESWL). However, for stones that are poor candidates for this modality, endoscopic therapy is indicated. Ureteroscopy is the most common means of visualizing an upper urinary tract calculus. In addition, percutaneous techniques (eg, percutaneous endourology) can also be used.

Depending on stone size and location and associated ureteral obstruction, various treatments can be used. Most ureteral stones are small (< 5 mm) and should pass spontaneously without surgical intervention. Larger stones (< 1.5 cm) that are not associated with complete ureteral or renal obstruction can frequently be treated with ESWL in a noninvasive manner.

Endoscopic treatment is most commonly used to manage obstructive and/or large stones. Most infectious calculi are large and are usually located in the kidney. Thus, these are also commonly treated with endoscopy. In these scenarios, retrograde ureteroscopic lithotripsy or percutaneous nephrostolithotomy is used.

Intravenous pyelography defines a functioning kidn Intravenous pyelography defines a functioning kidney with a large branching intrarenal stone burden.

This article reviews the available endoscopic lithotrites and their clinical applications.

History of the Procedure

Endoscopic lithotrites include ultrasonic, electrohydraulic (EHL), and mechanical devices, as well as various lasers. These instruments are passed through the working channel of the endoscope to fragment stones into extractable pieces. Baskets and graspers are used during lithotripsy to immobilize stones and to remove stone fragments.

Ultrasonic lithotripsy

Ultrasonic lithotripsy was used initially. This modality requires a rigid endoscope and is commonly used via a percutaneous renal approach. It is less useful with ureteroscopy.

Electrohydraulic lithotripsy

EHL probes deliver energy via 2 coaxial electrodes. Ignition creates a small spark of high temperature that vaporizes a small volume of water into a gaseous bubble. The bubble expands circumferentially. Power is proportional to the diameter of the probe. Drawbacks of EHL lithotripsy include its potential for damaging adjacent tissue, producing large fragments, and occasionally failing to fragment the hardest calculi, including calcium oxalate monohydrate.

Mechanical lithotripsy

Pneumatic mechanical devices, such as the Lithoclast, are small endoscopic jackhammers that work best when passed through a straight endoscopic working channel. With reusable stainless steel probes, the Lithoclast can be used through rigid or semirigid endoscopes. The Lithoclast is an efficient and economical means of fragmenting calculi and is particularly useful for managing large and hard stones. It is commonly used for large renal stones (percutaneously) and distal ureteral stones (ureteroscopically).

Laser lithotripsy

Laser lithotripsy was first introduced commercially in the late 1980s with the pulsed-dye laser, which uses 504 nm of light delivered through optical quartz fibers. This was a nonthermal safe laser that produced plasma between the tip of the fiber and the calculus, fragmenting stone with a photo-acoustic effect. The small flexible probes complemented both the semirigid and flexible ureteroscopes and could fragment most urinary calculi, excluding cystine. However, this was not a solid-state laser, and it required frequent maintenance, including changing of the coumarin dye. The energy available at the tip of the fiber is proportional to the fiber diameter. The 200-µm fiber allows the most endoscopic deflection but can deliver only 80 mJ of energy, which is frequently insufficient to fragment calcium oxalate monohydrate calculi.

Advancing laser technology has led to the development of the holmium:YAG (yttrium-aluminum-garnet) laser, which is a thermal laser that uses a 2150-nm wavelength of light. The energy is delivered in a pulsatile fashion through low–water-density quartz fibers. Johnson studied the soft-tissue effects of this laser and found that the thermal effect of this laser within a water-based medium was confined owing to a vaporization bubble formed at the tip of the fiber.[1] In 1995, Matsuoka et al presented the first clinical series of endoscopic lithotripsy with this wavelength and found it to be safe and efficient in treating ureteral stones.[2] As opposed to the coumarin pulsed-dye laser, holmium laser lithotripsy produces smaller fragments that can be, in part, irrigated from the collecting system during treatment.

This is an endoscopic image of a holmium laser fib This is an endoscopic image of a holmium laser fiber fragmenting a stone burden.

The energy available at the tip of the holmium laser does not depend on the diameter of the fiber. Techniques used to increase treatment efficiency by varying fiber diameters with complementary endoscopes have been described. These techniques involve larger fibers complemented by increased stiffness, which decrease the flexibility of the endoscope.

For additional information, see Medscape Reference’s Lasers in Urology article.

Indications

Ureteroscopic lithotripsy as a common treatment for distal ureteral stones began in the early 1980s. During the same period, ESWL was introduced as a treatment for uncomplicated, moderately sized renal calculi.

  • While ureteroscopy progressed over the next 10 years, extracorporeal shockwave lithotriptors evolved to second-generation and third-generation devices that required fewer anesthetics during treatment but yielded lower stone-free rates and more related procedures than the first-generation machines.

  • New generators with smaller focal zones had focused shockwaves and required lower overall power.

  • The imaging on the newer extracorporeal lithotriptors allowed easier localization of ureteral stones, and there was great enthusiasm for treating stones throughout the entire upper urinary tract with this modality.

  • In certain cases, ureteral stents were also placed to localize stones in the ureter prior to shockwave lithotripsy and to ensure drainage of an obstructed upper urinary tract.

  • The newest devices did not obtain the success rates of the first-generation Dornier HM3.

In the early 1990s, the American Urological Association (AUA) developed guidelines for treating calculi. The guidelines were based on published clinical experience with ESWL and endoscopic lithotripsy.

  • The first guidelines panel dealt with the treatment of large renal stones (>2.5 cm). In this study, the AUA panel suggested that percutaneous nephrostolithotomy was superior to shockwave lithotripsy for such stones.

  • The second guidelines panel addressed the treatment of ureteral calculi. Treatment was stratified by stone size and location and other considerations. The panel suggested that stones smaller than 5 mm that are unassociated with high-grade upper urinary tract obstruction frequently pass without surgical intervention. The panel also suggested that patients with such stones but without prolonged, symptomatic, or complete upper urinary tract obstruction or associated infection should be monitored clinically.

  • The AUA panel recommended that larger ureteral calculi and those associated with significant obstruction can be treated with either ESWL or ureteroscopic lithotripsy. The most recent clinical series have found shockwave lithotripsy based on the newest extracorporeal lithotriptors to be less invasive and less efficient in treating ureteral stones, with fragment clearance often requiring as many as 4 months of follow-up.

  • Ureteroscopic treatment of renal calculi is gaining popularity because of the recognition of limitations of ESWL. Although ESWL is associated with minimal morbidity, its effectiveness is decreased in the treatment of certain stone compositions (eg, calcium oxalate monohydrate, cysteine), large stones, and stones located in the lower pole.

Flexible ureteroscopy with holmium laser lithotripsy is an attractive alternative to shockwave lithotripsy in the management of renal calculi in anomalous and/or ectopic kidneys (ie, horseshoe kidneys). In addition, ureteroscopy is a primary treatment in select patients with symptomatic stones in pelvic kidneys.

Certain patients or stone characteristics may favor ureteroscopic lithotripsy over ESWL or percutaneous nephrolithotripsy (PCNL). These include the following:

  • Lower-pole stone location

  • Cysteine or calcium oxalate monohydrate stone composition

  • Morbid obesity

  • Uncorrectable bleeding diathesis

  • Stones within a calyceal diverticulum or infundibular stenosis

  • Ectopic kidney

Contraindications

No contraindications to endoscopic lithotripsy exist, with the exception of those associated with endoscopy.

 

Workup

Laboratory Studies

No specific laboratory tests are required beyond those associated with the endoscopy, ie, coagulation profile, CBC count with a platelet count, electrolytes, BUN, and creatinine.

 

Treatment

Surgical Therapy

Ultrasonic lithotripsy

See the list below:

  • This used most commonly via a percutaneously placed rigid endoscope.

  • This form of endoscopic lithotripsy requires a straight working channel because power is decreased significantly with any endoscope deflection.

  • In addition, ultrasonic lithotripsy is used most commonly to manage infectious calculi in which the hollow core probe and suction can simultaneously fragment and evacuate stone particles.

    Treatment was based on percutaneous access and rig Treatment was based on percutaneous access and rigid endoscopic lithotripsy to clear the central stone burden with the hollow core ultrasonic lithotripter. On this image, a flexible nephroscope and holmium laser were also used to address portions of the stone burden inaccessible to the rigid equipment.

Electrohydraulic lithotripsy

See the list below:

  • These probes are based on sparking an electrode on a wire cable that can be placed through rigid or flexible endoscopes.

  • These fragment stones into extractable pieces but are less efficient than holmium:YAG lasers on the hardest calculi.

  • In most centers, this form of endoscopic lithotrite has been replaced and/or supplemented by holmium lasers.

Mechanical and ballistic lithotripsy

See the list below:

  • These devices are powerful and based on pneumatically driven projectiles that strike a metallic probe placed endoscopically on a calculus. Commonly, the created fragments require extraction with either an endoscopic basket or grasper.

  • These devices work best when they are used through a rigid endoscope, and they can be associated with stone migration during treatment.

  • The flexible pneumatic lithotripsy probe was developed to complement flexible endoscopes. Tip displacement and fragmentation ability of the probe have been shown to be inversely related to the degree of active deflection of the ureteroscope; thus, this has minimal clinical usefulness.

Laser lithotripsy

See the list below:

  • The pulsed-dye laser was the first commonly used laser lithotripter.

  • When using a light energy of 504 nm delivered in a pulsatile fashion through quartz fibers, calculi are fragmented.

  • A photo-acoustic effect forms plasma between the tip of the fiber and the calculus, fragmenting stones along fracture planes.

  • The deliverable energy is limited by fiber diameter, with the smallest fibers able to deliver only 80 MJ, which is often insufficient to fragment the hardest stones. In addition, this laser energy has little effect on cystine calculi; 504 nm of light energy passes through this crystal rather than creating the aforementioned plasma on the surface.

  • Various lasers used in lithotripsy include the following:

    • Holmium:YAG laser

      • The holmium:YAG laser is one of the most commonly used lasers and has been universally accepted as the standard for intracorporeal lithotripsy.[3] Multiple recent studies have demonstrated that holmium:YAG laser lithotripsy is superior to electrohydraulic lithotripsy, ultrasonic lithotripsy, and pneumolithotripsy in terms of stone fragmentation and complications.

      • Using 2150-nm light energy in a pulsatile fashion, this thermal laser produces a vaporization bubble at the tip of low–water-density quartz fibers. Even with the small 150- to 200-µm fibers, the energy delivered is sufficient to fragment all types of urinary stones into fine dust and small pieces that can then pass easily through the urinary tract. Therefore, hard stones in difficult locations (eg, lower-pole calyx) can be treated using a small-diameter fiber that is easily deflected with the ureteroscope.

      • Holmium laser energy is rapidly absorbed by water, creating a vaporization bubble that has minimal effects on adjacent tissue (2-3 mm from the fiber tip). These qualities result in minimal adjacent tissue trauma. However, direct contact with tissue should be avoided unless tissue resection is planned. In addition, sufficient cooling irrigant through the endoscope should be used to prevent adjacent thermal soft-tissue effects.

      • Holmium laser lithotripsy is more effective than other endoscopic lithotrites for large and complex stone burdens composed of uric acid or cystine.[4]

    • Frequency-doubled, double-pulse neodymium:YAG (FREDDY) laser

      • The FREDDY laser is a neodymium:YAG double-pulse laser.

      • Recent work in Europe has shown that the FREDDY laser is inferior to the holmium:YAG laser in lithotripsy. Whereas the holmium:YAG laser is controlled via a distal tip vaporization bubble that creates acoustic percussion waves that destabilize and fragment stones, neodymium:YAG, even when pulsed, is a high-temperature laser with limited fragmentation capabilities for hard stones and causes significantly greater stone retropulsion. In addition, the FREDDY laser is less versatile and is unable to treat urinary-tissue lesions.[5]

    • The erbium:YAG laser and the thulium:YAG laser are two newly developed lasers being tested in clinical and in vitro trials to improve the efficiency of stone lithotripsy in the future. Fiber delivery for the both lasers is still in its infancy.[6, 7]

    • The video below depicts ureteroscopy and holmium laser lithotripsy.

      Ureteroscopy and laser lithotripsy. Video courtesy of Dennis G Lusaya, MD, and Edgar V Lerma, MD.

Intraoperative Details

Endoscopes: Please refer to the Medscape Reference article Ureteroscopy.

Bladder stones

Rigid, continuous-flow cystoscopic equipment is preferred to treat bladder stones. In addition, a large-caliber resectoscope sheath and laser bridge is a very efficient means of delivering the 1000-µm holmium laser fiber. The larger laser fiber produces a sizable vaporization bubble in saline irrigant, allowing the surgeon to sculpt stone into dust rapidly, while the large sheath keeps the operating field clear be facilitating evacuation of the created debris.

Ureteral stones

Distal ureteral stones are addressed with semirigid endoscopes ranging in diameter from 4.5F-9F. These fiberoptic-based endoscopes can be angled approximately 30° while maintaining clear optical images. Many of the endoscopes are based on a 2-channel system. This allows the surgeon to simultaneously use both an endoscopic lithotrite and basket or grasper. This is particularly useful when a stone is mobile in a dilated ureter. In this case, a basket, or Stone Cone device, can be used to prevent stone migration while the laser is used to sculpt the stone into an extractable core fragment.

Proximal ureteral stones are frequently treated with actively deflectable flexible ureteroscopes. These endoscopes are most commonly smaller than or equal to 8.5F in diameter and have only a single working channel. The smallest-diameter lithotrites are used through these endoscopes. One operative strategy with mobile stones in the proximal ureter is to position the patient in the Trendelenburg prior to endoscopic manipulation. If proximal stone migration is noted during endoscopic lithotripsy, the flexible endoscope can follow the stone into an upper- or middle-pole calyx, where it is more stable and can fragment quickly with the laser lithotripter.

Renal stones

Retrograde ureteroscopic treatment of intrarenal calculi is performed with actively deflectable flexible ureteroscopes. The smallest-diameter lithotripsy probes (eg, 200-µm laser fiber, 1.4F EHL probe) are required to treat lower-pole calyceal calculi.

Percutaneous nephrostolithotomy is performed with both rigid and flexible endoscopes. Rigid nephroscopes usually have offset lens systems to facilitate the straight ultrasonic lithotripsy probes. These probes are hollow and allow for simultaneous evacuation of debris during fragmentation. This is useful for treating infectious, matrix-based, staghorn calculi.

Staghorn renal calculus is noted on plain radiogra Staghorn renal calculus is noted on plain radiograph of the abdomen.

Flexible nephroscopy is usually performed after the rigid nephroscope and ultrasonic lithotripter have cleared a large, central, stone burden and peripheral calyceal calculi remain. The rigid endoscope is often prohibited access to these peripheral stones, while the flexible 15-18F nephroscope can direct a lithotrite safely onto them. The same flexible lithotripsy probes used for ureteroscopic lithotripsy are passed through the large (>6F) working channel. Nitinol basket extractors are also commonly passed through the flexible nephroscope to extract the remaining small stones and fragments.

All endoscopic lithotrites are used under direct vision through the working channel of an endoscope.

Endoscopic baskets can also be used, most often through a dual-channel rigid endoscope, to stabilize a mobile stone during fragmentation.

Take care when using the holmium:YAG laser in this setting because the laser can easily damage the wires of the basket. Basket fragmentation may lead to foreign bodies within the urinary collection system.

Ureteropyeloscopic treatment of large upper urinary tract calculi

Ureteroscopic treatment of large, noninfected upper urinary tract calculi was first described in 1998 in patients with comorbidities prohibiting percutaneous nephrostolithotomy, who were accrued and treated with retrograde endoscopic techniques.[8] The most recent series was based on 145 patients with 164 stone burdens in excess of 2 cm in diameter, including 36 partial staghorn calculi.[9] The stone-free rate at 3 months was 87%, with an average of 1.6 procedures per patient with minimal complications.

Technically, the procedure begins in a similar fashion to any flexible ureteropyeloscopic procedure. The flexible ureteroscope and laser lithotripter are used to fragment the calculus into fine dust and small residual passable debris smaller than 3 mm. A 14F Foley catheter is placed transurethrally next to the flexible ureteroscope to maintain continuous bladder drainage during the procedure.

Ureteroscopic fragmentation continues until the endoscopic field of view is obscured by dust or debris. All patients are counseled that second-stage ureteroscopy may be required to clear the stone burden. At the conclusion of endoscopic lithotripsy, large-caliber ureteral stents (8-10F) are used to maximize drainage and to passively dilate the ureter overtime, which ultimately helps clear stone debris.

Most importantly, patients with infectious struvite calculi or infected stones are poor candidates and should not be offered this treatment, in that there is a higher risk of perioperative infectious complications. Additionally, residual infectious stone debris may act as a nidus for stone regrowth and future infections. These patients should undergo a percutaneous nephrostolithotomy unless contraindicated.

Postoperative Details

Internal ureteral stents are often placed after ureteroscopic lithotripsy to help facilitate healing and to ensure drainage, particularly if vigorous therapeutic maneuvers were performed. Internal stents may minimize the risks of urinomas (collections of urine outside the urinary collecting system) and/or ureteral strictures after traumatic endoscopy.

Internal ureteral stents commonly cause lower urinary tract symptoms, which include urinary frequency, urgency, and mild-to-moderate transient hematuria.

The ureteral stents are removed after a period of healing, ranging from a few days to 6-8 weeks, depending on the complexity of the treatment. Stents are usually removed in the office with either an attached nylon suture left through the urethra postoperatively or cystoscopically.

Patients are discharged on oral antibiotics, analgesics, and, occasionally, anticholinergic medication to decrease symptoms associated with the ureteral stent. Antibiotics are commonly used to eliminate any bacteriuria after all tubes have been removed.

Follow-up

For excellent patient education resources, see eMedicineHealth's patient education articles Kidney Stones and Intravenous Pyelogram.

Complications

The complications of intracorporeal lithotripsy include problems associated with the endoscopy (potentially, trauma to the urinary tract) and the specific problems created by incomplete stone fragmentation and incomplete fragment elimination.

Incomplete and/or inadequate pulverization of the stones occasionally occurs with all types of lithotripsy. The residual fragments can lead to renal or ureteral colic and secondary procedures.

Outcome and Prognosis

The endpoint of endoscopic lithotripsy has changed based on new technology. Stone extraction was once commonly used; today, however, devices such as the holmium laser allow the surgeon to safely convert the stone burden to fine particulate debris. This debris is partially irrigated from the collecting system during the procedure or allowed to pass over time.

  • Studies indicate that holmium:YAG lithotripsy is associated with shorter operative time and postoperative hospitalization period than lithoclast lithotripsy for ureteral stones. Data also suggest that holmium:YAG lithotripsy is safe and more effective than lithoclast lithotripsy, with significantly better immediate stone-free rates.

  • The holmium:YAG laser lithotripter can fragment and destroy all compositions of stone. The stone-free rate for ureteral stones approaches 100%. The overall success rate for ureteroscopic treatment of renal stones varies from 75-92%. Complications are rare and minimal when used with the current technique.

Ultrasonic lithotriptors used only through rigid endoscopes provide high fragmentation rates (97-100%) and stone-free rates (94%). Limitations are based primarily on failure of endoscopic access, since this class of lithotrite cannot be deflected significantly and is thus not complementary with semirigid or actively deflectable flexible ureteroscopes.

Future and Controversies

Traditional open surgical lithotomy procedures have been replaced by extracorporeal, intracorporeal, and percutaneous lithotripsy. Extracorporeal lithotripsy is the least invasive method for eliminating stones, but it has a relatively high failure rate with large stones, obstructing stones, cystine stones, and other complex stones. Intracorporeal lithotripsy is minimally invasive and yields high success rates with most ureteral stones and renal stones.[10] The holmium:YAG laser is currently the most effective and widely used laser available today. Current studies are investigating newer lasers and devices to continually improve the efficiency, cost, and visualization of stone fragmentation via an endoscopic approach.

Controversy still exists about the preferred endoscopic approach, percutaneously through the kidney versus ureteroscopically. The preferred approach is the one that, in the hands of the operator, offers the greatest chance of rendering the patient stone-free with the least morbidity and expense. Therefore, for most urologists, the preferred approach is strongly influenced by the number, size, location, and probable composition of the stone(s) and by the body habitus of the patient.