Intracorporeal Lithotripsy Treatment & Management

Ultrasonic lithotripsy

• 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 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

• 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

• 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

• 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. 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.
  • 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.^[3]
  • 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.^{[4, 5]}
  • 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.

Endoscopes: Please refer to the eMedicine 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.

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.

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.

For excellent patient education resources, visit eMedicine's Kidneys and Urinary System Center. Also, see eMedicine's patient education articles Kidney Stones and Intravenous Pyelogram.

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.

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.

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. 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.